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Jorge
2005-Jul-15, 09:55 PM
Would it be possible to use a large catapult to shoot things into a orbit around earth?

or a combination of a catapult and rockets to save on fuel costs?

Zamzara
2005-Jul-15, 10:26 PM
Very unlikely.

Any system that worked like that would have to be very long indeed, to reach the speeds necessary at a reasonable rate of acceleration, and very very high as well, to protect the payload from atmospheric heating.

Jorge
2005-Jul-15, 10:49 PM
A long underground tunnel with that strongy curves upwards at the end?

gopher65
2005-Jul-16, 12:55 AM
Are you talking about a magnetically accelerated launching apparatus? If so, I think it would be a good idea for microsatellites :). Especially if they can make them maybe 10 or 20 cm in diameter.

It would be sorta like a really big rail gun.

Jorge
2005-Jul-16, 01:07 AM
I was thinking long the lighs of using magnets yes, but not sure that would be good for the stuff we lauch.

I wasn't thinking big stuff. i was thinking like
small comunication stalites and stuff.

Kaptain K
2005-Jul-17, 06:08 AM
Considering how much of the take-off weight is fuel and how much of that fuel is used just to accelerate that mass of fuel to a couple of kilometers of altitude and a few hundred kilometers/hour, I think that the concept of using a catapult as a first stage is not only possible, but could be very feasible financially.

Jorge
2005-Jul-17, 08:28 AM
Considering how much of the take-off weight is fuel and how much of that fuel is used just to accelerate that mass of fuel to a couple of kilometers of altitude and a few hundred kilometers/hour, I think that the concept of using a catapult as a first stage is not only possible, but could be very feasible financially.

that was more or less the idea, to cut costs for launching statelites,

using less fuel = less payload = less money

Jens
2005-Jul-17, 02:58 PM
Very unlikely.

Any system that worked like that would have to be very long indeed, to reach the speeds necessary at a reasonable rate of acceleration, and very very high as well, to protect the payload from atmospheric heating.

I think these are significant issues. On one hand, it's true that a lot of the fuel spent at the beginning is used to accelerate other fuel, so therefore the catapult idea makes sense.

But on the other hand, I think the catapult idea is counterindicated by the fact that the atmosphere, and hence drag, is thickest at low altitude and becomes thinner as one gets higher. Thus, it makes sense to have the rocket move slowly at low altitudes and then go faster as it gets higher, which is what they do today.

For this reason, I think the idea of using balloons to bring a payload to high altitude, and then use rocket fuel beyond that, is really a better solution than a catapult, unless you can somehow get the catapult high in altitude.

Jorge
2005-Jul-17, 07:31 PM
building the ramp on the slope of a hight mounten could work to get it a bit higher

JohnD
2005-Jul-18, 11:57 PM
Jorge,
You're not the first to think of this.
George Pal, the legendary SciFi film director used it in "When Worlds Collide". See: http://www.aldrichastro.org/orbit.html

John

Jorge
2005-Jul-19, 12:03 AM
Jorge,
You're not the first to think of this.
George Pal, the legendary SciFi film director used it in "When Worlds Collide". See: http://www.aldrichastro.org/orbit.html

John

Never claimed i was first lol,

I actualy got it from a japanese anim series TekkaMan or something do'nt understand much of it lol

AGN Fuel
2005-Jul-19, 12:51 AM
Very unlikely.

Any system that worked like that would have to be very long indeed, to reach the speeds necessary at a reasonable rate of acceleration, and very very high as well, to protect the payload from atmospheric heating.

I think these are significant issues. On one hand, it's true that a lot of the fuel spent at the beginning is used to accelerate other fuel, so therefore the catapult idea makes sense.

But on the other hand, I think the catapult idea is counterindicated by the fact that the atmosphere, and hence drag, is thickest at low altitude and becomes thinner as one gets higher. Thus, it makes sense to have the rocket move slowly at low altitudes and then go faster as it gets higher, which is what they do today.

Your payload would have to be quite..er..sturdy, as well. The g-forces in a catapult system would be phenomenal! :o

PatKelley
2005-Jul-19, 01:59 AM
Just go for a big coil-driven gun. Wrap enough copper cable around a redirected iron sewer conduit, and voila! You can control the acceleration, the cylindrical cargo is both suspended and imparted some spin by the conduit, and if you have enough length you can work your way up to phenomenal speeds, cutting a path through the air by hitting it with a laser and turning the air in the way into a plasma.

But again, all of this is purely speculative.

Sock Munkey
2005-Jul-19, 07:58 AM
Our best bet is to run the track up the side of the Andes at the equator where the air is nice and dry and we can get as much of a boost from the spin of the earth as possible. If the track can accelerate the craft to over 600kph it can use ramjets from that point untill the air gets too thin and only then does it need to run its' engines off internal oxygen.

I have a clever little notion that would further increase the performance of said craft.

Scooping up atmospheric air into those of its' fuel tanks which have been spent on the way into the upper atmosphere would mean that it could get by with a smaller LOX tank.

Maksutov
2005-Jul-19, 11:47 AM
I'm reserving judgment on this subject until Trebuchet (http://www.badastronomy.com/phpBB/profile.php?mode=viewprofile&u=4533) checks in.

Ilya
2005-Jul-19, 01:42 PM
The biggest problem I see with magnetic catapult is keeping the entire length of it free of air. Maintaining vacuum integrity in a tube tens of kilometers long is EXPENSIVE. Especially since it will necessarily refill with air at every launch.

Note that I said "expensive" not "insurmountable". From engineering standpoint it is not a complicated task, but it can easily eat up all cost savings compared to a rocket.

PatKelley
2005-Jul-19, 01:51 PM
Maybe a close cost to rocketry, except that it is immediately reusable. You could even send up trains of objects if you got the timing right.

Early speculation on coil vs. rail guns speculated a muzzle velocity of 6 miles per second was possible, if difficult - and with small projectiles, would make almost any armor useless. Would mean less complicated targeting algorithms as a 10 meter drop after one second would be a minor deflection if the target was 1/4 mile away... and the lack of explosive propellant means it would be possible to fire multiple projectiles in series. An extension of the solenoid.

Early railgun experiments caused rattling towards the end of the track as the "sled" was not perfectly aligned, and at higher velocities this meant minor deflections would destroy the track by the second or third firing. The coilgun was cited as a possible solution to this (back in 1993, if I'm not mistaken) and goodness knows what's been done since. It provided the above advantages to stabilizing and imparting spin to the projectile. As far as evacuating air... depends on the length of your tube, I suppose.

Zamzara
2005-Jul-19, 03:49 PM
I was originally thinking about a literal elastic-type catapult in my first post. I agree that a magnetic system would be far more feasible.

skrap1r0n
2005-Jul-19, 04:42 PM
Ben Bova used the idea of a rail ramp in his Moon War series. Of course, it was on the moon so Escape velocity was much less. I believe the real issue with it here on earth is air resistance.

There have been thoughts along the line of making the first few stages of the trip in a vaccum tunnel and only using rail tech to accellerate a scramjet to the needed speed in order for them to activate.

The problem is exiting the tunnel. Unless, as mentioned before it was run up the Andes then exiting to the atmosphere would not be unlike hitting water. Besides, you would have the same issues with heat shielding on the way up as well as the way down.

This brings up an intertesting question though. Is there a maximum speed solid matter can reach in a pressurized atmosphere? I mean if heat wasn't an issue, would there be an absolute limit to how fast something can travel through the atmoshere?

Another thought... Would it be possible to have some type of Plasma beam or something that would effectivley burn a hole in the atmosphere to eliminate any air pressure for the craft following it?

Ilya
2005-Jul-19, 06:09 PM
This brings up an intertesting question though. Is there a maximum speed solid matter can reach in a pressurized atmosphere? I mean if heat wasn't an issue, would there be an absolute limit to how fast something can travel through the atmoshere?

Well, if you hit the atmosphere from outside, then there is no limit -- although you may get a spectacular explosion. Your question, however, seems to be "how fast can an object get if it accelerates from standstill within atmosphere?" Assuming infinitly heat-tolerant materials, I don't think there is a limit -- or rather, your energy source becomes the limit. At supersonic speeds air resistance is proportional to the square of velocity, so the faster you, the (much) more energy it takes to gain next meter/second. At some point resistance becomes equal to thrust, and you can't accelerate any more.

Trebuchet
2005-Jul-19, 07:18 PM
I'm reserving judgment on this subject until Trebuchet (http://www.badastronomy.com/phpBB/profile.php?mode=viewprofile&u=4533) checks in.

Now I'm dreaming of orbiting pumpkins!

This has actually been discussed on the Catapults Message Board (http://www.thehurl.org). Consensus was it isn't practical, although I could see a rail gun on the moon having some application.

PatKelley
2005-Jul-19, 07:25 PM
Done some calculating, and postulating a device of sufficient capacity (haven't done the electronics for this) - a released cargo module would have to be at approximately 7.72 km per second traveling east to achieve a 200 km orbit (roughly Mach 22 at sea level). Rather than pumping a tube free of air, heating the air to a plasma at 12,000 to 15,000 degrees would reduce the pressure to approximately 1/40 of atm, presuming room temperature air. Granted, one is trading heat for heat, but at least forward resistance is reduced, and could be extended for a region in front of the muzzle for however long it would be feasable and practical.

However, acceleration is another matter. To achieve an even acceleration to 7.72 km/s at sea level requires accelerating at 1 G for 788 seconds over a distance of 3,000 km. At 5 G's, for 157 seconds over a distance of 600 km, and at 20 Gs for 39 seconds over 150 km.

This all assumes linear. I'm fairly certian that containment at higher speed would generate enough force to smash flat any elements in a circular track before launch.

In short, unless somebody has a disused tunnel of appreciable length and cargo capable of sustaining 40 seconds of 20 G's... my own idea is unlikely.

Jpax2003
2005-Jul-20, 07:01 PM
I think Heinlein suggested a tall mountain with a long eastward slope would be ideal in his novel, The Moon Is a Harsh Mistress. He suggested Nanda Devi in northern India might work. I always thought that the Altaplano in South America might be workable.

Last week I was driving down the road and saw an image in my mind of a highway of light going up into the sky. Upon reflection I think it was the idea of driving a space capable car onto an electromagnetic highway. As it ramps up the vehicle is ejected into the air where high power lasers push it the rest of the way to a skyhook where it is captured and then eventually released in a lunar trajectory. The idea of individual random access to space is fanciful but I wonder if that particular sequence of staging is possible.

I have also thought about using a two-stage system using an air breathing first stage. This would not be for lofting really heavy items, but might be for small passenger shuttles. Basically, a winged mothership powered by turbojets at low altitude with ram/scramjets at higher altitude lifts a Passenger Shuttle Craft on a ballistic trajectory where the PSC is released at the apex. The PSC then launches the rest of the way using a disposable rocket booster. The mothership returns and is reused. The PSC disposable rocket motor is either deorbited or left in orbit as scrap where it's valuable material may be used to make a station in orbit or on the moon.

publiusr
2005-Jul-20, 10:06 PM
All rocket propulsion is still best for now. Movies like Star Wars have spoiled people into hating rockets, and got people to call them 'primative' 'wasteful' etc.

So we get cranks with anti-gravity, space-elevators--and folks fall all over themselves to keep from building bigger rockets--convincing themselves it is 'too expensive' as if their own Rube Goldberg contraptions aren't.

Jpax2003
2005-Jul-21, 12:02 AM
All rocket propulsion is still best for now. Movies like Star Wars have spoiled people into hating rockets, and got people to call them 'primative' 'wasteful' etc.

So we get cranks with anti-gravity, space-elevators--and folks fall all over themselves to keep from building bigger rockets--convincing themselves it is 'too expensive' as if their own Rrube Goldberg contraptions aren't.

I do agree with that. I think that John Walker's Rocket-a-Day (http://www.fourmilab.ch/documents/rocketaday.html) makes it clear that an economy of scale would greatly reduce the cost of space access. However, I think we'd need heavy lift in addition to John Walker's hypothetical ubiquitous rocket that carries 2000 kg. My multistage design uses an air breathing lower stage for lofting a small passenger shuttle in order to increase comfort and safety. Range safety is the only real concern for cargo, which should be lifted on the likely cheaper and more efficient rocket-only stack.

This is why I propose a heavy-duty lunar colony as a primary goal. It would require the use of many medium to large rockets lifting construction materials into LEO or lunar transfer orbits. The more rockets we launch the lower the cost per launch. I suspect that the cost may eventually reach a 10:1 or even a 100:1 launch cost ratio to the NASA STS. We no longer ship goods across the ocean in ships like the Nina, Pinta, and Santa Maria, we use ships like the Columbo Express that carry thousands of times more cargo more safely and more efficiently and more quickly with the complementary analog of UPS 747s. It's time we made an economy class form of spaceflight.

Charlie in Dayton
2005-Jul-21, 01:50 AM
You also have to keep in mind the acceleration limits of the cargo/passengers. Sudden application of acceleration (such as would be seen with the equivalent of firing them from a cannon) would render the occupants into a thin red organic paste...

gopher65
2005-Jul-21, 03:04 AM
I think this was meant only for small, hardened satellites and probes. No passengers allowed:)

Sock Munkey
2005-Jul-21, 04:48 AM
Bob Truax was right all along.

publiusr
2005-Jul-21, 04:51 PM
He certainly was. He had a great article in Aerospace America that I haven't found a link too--speaking on how upper stages cost as much if not more than the first stages.

Truax is in bad health these days. There are two people in his footsteps. One is Bill Sprague over at www.aeraspace.com I think--the other is John London over at Marshall who--like Truax--is a big pressure fed advocate. Rocket-a-day is nice for transfer of light articles--but simple heavy-lifters like Truax's Sea Dragon are what we really need. Griffin's HLLV is a step in the right direction.

John London's book LEO ON THE CHEAP should be available on the web if you want to look it up. He works at Marshall now with Bob Sackheim.

http://www.dunnspace.com/leo_on_the_cheap.htm

Big Pressure-Feds of the Truax kind:

http://www.astronautix.com/lvs/searagon.htm
http://www.astronautix.com/lvs/bealba2.htm

Faultline
2005-Jul-24, 05:59 AM
When you launch a rocket, you have a reaction mass pushing (accelerating) the craft for as long as you have fuel.

With a catapult, wether it comes from ACME or is a futuristic E-Mag device, you have to get ALL of your orbital velocity at once, for your craft will immediately begin to slow down right after leaving the cup/barrell. Air friction and gravity will go to work immediately.

That's an awful lot of G forces on your payload. If it's human payload, they'd be strawberry jam in a microsecond. If it's electronics, better make sure they're more solidly built than my first VCR.

Faultline

Jpax2003
2005-Jul-25, 08:06 AM
When you launch a rocket, you have a reaction mass pushing (accelerating) the craft for as long as you have fuel.

With a catapult, wether it comes from ACME or is a futuristic E-Mag device, you have to get ALL of your orbital velocity at once, for your craft will immediately begin to slow down right after leaving the cup/barrell. Air friction and gravity will go to work immediately.

That's an awful lot of G forces on your payload. If it's human payload, they'd be strawberry jam in a microsecond. If it's electronics, better make sure they're more solidly built than my first VCR.

Faultline

A catapult might increase velocity over longer distances to keep acceleration below the strawberry-jamification level.

Faultline
2005-Jul-25, 01:44 PM
When you launch a rocket, you have a reaction mass pushing (accelerating) the craft for as long as you have fuel.

With a catapult, wether it comes from ACME or is a futuristic E-Mag device, you have to get ALL of your orbital velocity at once, for your craft will immediately begin to slow down right after leaving the cup/barrell. Air friction and gravity will go to work immediately.

Faultline

A catapult might increase velocity over longer distances to keep acceleration below the strawberry-jamification level.

How can a catapult increase velocity over longer distance than a rocket? The rocket fires reaction mass out its back end the whole way up! A catapult has to get the object to escape velocity by the time it reaches the end of the catapult! Is this catapult 60 miles long? Really?

Faultline

Jpax2003
2005-Jul-25, 05:53 PM
How can a catapult increase velocity over longer distance than a rocket? The rocket fires reaction mass out its back end the whole way up! A catapult has to get the object to escape velocity by the time it reaches the end of the catapult! Is this catapult 60 miles long? Really?

Some published designs are hundreds of km long.

Faultline
2005-Jul-25, 06:49 PM
Some published designs are hundreds of km long.

What would be the point? So it launches on a rail that lays on the ground (or in the ground) and leaves the end of it fast enough to make it to orbit. That means it needs enough velocity to overcome gravity and air resistance for the trip out of the atmosphere and still have enough left over to break into orbit at 17,500 or so mph.

It would be like a meteor headed upwards, with a re-entry flame surrounding it. Jeez! With that much aerobraking, how much initial velocity would it need to make it to an altitude of 60 miles when it loses its propulsion the instant it leaves the catapult?


Can someone calculate the g-forces of accelerating to orbital velocity (plus the velocity needed to overcome the loss from gravity and aerobraking) within 100 kilometers?

Faultline

PatKelley
2005-Jul-25, 07:00 PM
Done previously here. (http://www.badastronomy.com/phpBB/viewtopic.php?p=505375#505375)

With several measures of speed-to-orbit-velocity assuming an eastward trajectory and calculating for constant accelerations of 1G, 5G and 20G. The atmosphere is thinning rather than thickening going up, and additionally creating a plasma-pathway with a laser was brought up (reducing atmospheric density to 1/40 atm). Still, the 20G path would take 150 km. Not infeasable, but a possible route for cargo and raw materials to orbit.

Jpax2003
2005-Jul-25, 07:27 PM
I couple of the proposals I read were 300 to 500 km long. Perhaps not likely but possible, at least with a modest increase in materials science. These proposals were to have an ejection end in the mountains for lower atmospheric density. Some have proposed using rocket boosters on the catapult pod (catapod?) in order to reduce the necessary velocity at ejection and, thus, reduce the length of the catapult. Of course, some have proposed floating the entire 100 km length of the catapult in the air with balloons to reduce atmospheric density.

As for the point, I think those that propose such designs suppose it will be less wasteful of resources, less polluting, cheaper, more accessible, and safer.

Faultline
2005-Jul-25, 08:06 PM
Floating something that big in the air would be ludicrous.

300km to 500km long is preposterous. Yes, you'd reduce the g forces but I still believe you'd need an incredible amount of velocity to still be at orbital velocity after penetrating that much atmosphere and fighting gravity all the way up.

Faultline

Jorge
2005-Jul-25, 08:39 PM
Why not use rockets at a later stage to maintain the velocity?

a catapult to get it a a nice speed, and then rockets to carry it onwards into orbit.

Jpax2003
2005-Jul-25, 08:54 PM
Floating something that big in the air would be ludicrous.

I thought so too. But I think SAMU was the proponent of that particular design, IIRC.


300km to 500km long is preposterous. Yes, you'd reduce the g forces but I still believe you'd need an incredible amount of velocity to still be at orbital velocity after penetrating that much atmosphere and fighting gravity all the way up.

Check out this wikipedia article (http://en.wikipedia.org/wiki/Mass_driver) for information on electromagnetic mass drivers.

CL8
2005-Jul-26, 01:13 PM
this is great but why not a floating platform that lanches the rockets from around 50 km up using lighter than air tech to suspend a rocket at the edge of the platform than use like compressed air to jet it off the platform than light and let it be on its marry way.

I unlike alot i see think that rockets have to be replaced by somthing more efffeceint.

Musashi
2005-Jul-26, 04:08 PM
What is the heaviest payload ever lifted by lighter-than-air technology?

Valiant Dancer
2005-Jul-26, 04:40 PM
What is the heaviest payload ever lifted by lighter-than-air technology?

From a cursory internet search, I get 3.5 tons (3182 kg approx.). (Stratoscope II, 1971)

Although NASA may have lifted a heavier payload in 1996 for balloon testing.

publiusr
2005-Jul-26, 08:00 PM
I couple of the proposals I read were 300 to 500 km long. Perhaps not likely but possible, at least with a modest increase in materials science. These proposals were to have an ejection end in the mountains for lower atmospheric density. Some have proposed using rocket boosters on the catapult pod (catapod?) in order to reduce the necessary velocity at ejection and, thus, reduce the length of the catapult. Of course, some have proposed floating the entire 100 km length of the catapult in the air with balloons to reduce atmospheric density.

As for the point, I think those that propose such designs suppose it will be less wasteful of resources, less polluting, cheaper, more accessible, and safer.

Kero/lox designs are clean compared to the av-gas (leaded gasoline) light aircraft use far more of--with R-7 by volume being an almost all LOX rocket with very small fuel tanks. Lox/LH2 burns to water.

it is best to buckle down--build big rockets--and leave Rube Goldberg in the comics, or on Nick-At-Night, next to Fibber McGee's closet.

Faultline
2005-Jul-26, 10:16 PM
Check out this wikipedia article (http://en.wikipedia.org/wiki/Mass_driver) for information on electromagnetic mass drivers.

Floating a 100km long E-mag catapult on a balloon? You know how much that would weigh? A lot more than 4 tons. A LOT MORE!

And I read the article. This system would work well on the lunar surface, where there is negligible atmosphere and far less gravity. On Earth, wind and gravity conspire to make it highly impractical.

Faultline

Jpax2003
2005-Jul-26, 10:31 PM
I couple of the proposals I read were 300 to 500 km long. Perhaps not likely but possible, at least with a modest increase in materials science. These proposals were to have an ejection end in the mountains for lower atmospheric density. Some have proposed using rocket boosters on the catapult pod (catapod?) in order to reduce the necessary velocity at ejection and, thus, reduce the length of the catapult. Of course, some have proposed floating the entire 100 km length of the catapult in the air with balloons to reduce atmospheric density.

As for the point, I think those that propose such designs suppose it will be less wasteful of resources, less polluting, cheaper, more accessible, and safer.

Kero/lox designs are clean compared to the av-gas (leaded gasoline) light aircraft use far more of--with R-7 by volume being an almost all LOX rocket with very small fuel tanks. Lox/LH2 burns to water.

it is best to buckle down--build big rockets--and leave Rube Goldberg in the comics, or on Nick-At-Night, next to Fibber McGee's closet.

It's not my idea, I'm just repeating the ideas of others here. I'm all for the brute force method of big dumb rockets. The only exception is that I would like to see a SSTO spaceplane become a reality. It's not an issue of efficiency or disposability but of ubiquity. Rockets generally require specialized launch facilities, but a spaceplane could possibly launch and land at any conventional airport. I was reading wikipedia articles about this last night and saw that some ideas are thought to have merit, such as the russian MAKS.

I was thinking of using a very small orbital passenger shuttle craft (PSC) that is launched from the back or belly of a supersonic or hypersonic mothership. The PSC would use a disposable rocket (LOX and R-7, or LH2 possibly) strapped to it's rear for propulsion after separation. The rocket booster would be scrapped in orbit and perhaps used for parts by an orbiting space facility. The PSC would carry one or two small space altitude rockets, as well as a cold reaction control system. It would also carry one or two small or moderate turbojets for use after re-entry. It would be a very small craft compared to the shuttle with a length of 70', a wingspan of 34' to 40' (considering an extendable wing for use in landing), and with a pressure hull of 8' dia. and 54' long. It would carry 14-21 passengers with a crew of 2-4 and luggage/cargo capacity of ~500 cuft or ~2500 lbs. I don't know if the design of the PSC is doable, much less the idea of hypersonic separation from a mothership, but I'm working on it as a proof of concept, or not.

Jpax2003
2005-Jul-26, 10:49 PM
Check out this wikipedia article (http://en.wikipedia.org/wiki/Mass_driver) for information on electromagnetic mass drivers.

Floating a 100km long E-mag catapult on a balloon? You know how much that would weigh? A lot more than 4 tons. A LOT MORE!

And I read the article. This system would work well on the lunar surface, where there is negligible atmosphere and far less gravity. On Earth, wind and gravity conspire to make it highly impractical.

Faultline

The highest payload from an aerostat? I don't know but I've read that the Hindenburg had a gross lift capacity of 242.2 tones and a useful lift of 112.1 tons. But don't talk at me about its nonfeasibility, I never thought it would work either. I think CL8 or SAMU proposed it last year.

As for earth based catapults, I yield to the authors of that article who probably know more about it thatn either of us. Some have suggested putting the ejection end on a mountain over 20,000 ft tall in order to reduce air resistance.

Bozola
2005-Jul-26, 11:12 PM
Heh! (http://www.badastronomy.com/phpBB/viewtopic.php?p=448501&highlight=#448501)

They all laughed!

Humots
2005-Jul-27, 02:25 AM
See:
http://xenotechresearch.com/?NewLoc=spa03.htm
http://www.homoexcelsior.com/omega.db/datum/megascale_engineering/lofstrom_loop/164
http://en.wikipedia.org/wiki/Lofstrom_loop

Humots
2005-Jul-27, 02:42 AM
Even better:
http://www.launchloop.com/

Kaptain K
2005-Jul-27, 06:18 AM
Your payload would have to be quite..er..sturdy, as well. The g-forces in a catapult system would be phenomenal!
Huh? The g-forces can be anything you want them to be!

v^2=2as

s=v^2/2a

Plug in the final velocity you want and the acceleration you can tolerate. The result is the length of catapult you need.

Suppose you can stand 3 g's and wish to reach 1000 kph (ramjet speed). You will need a catapult approximately 1.3 kilometers long. Commercial airport runways are a lot longer than that!

AGN Fuel
2005-Jul-27, 07:11 AM
Your payload would have to be quite..er..sturdy, as well. The g-forces in a catapult system would be phenomenal!
Huh? The g-forces can be anything you want them to be!

v^2=2as

s=v^2/2a

Plug in the final velocity you want and the acceleration you can tolerate. The result is the length of catapult you need.

Suppose you can stand 3 g's and wish to reach 1000 kph (ramjet speed). You will need a catapult approximately 1.3 kilometers long. Commercial airport runways are a lot longer than that!

I thought the intent was a realistic device that could send an inanimate payload into orbit? Obviously in that case, the launch velocity supplied by the catapult must be sufficient to overcome atmospheric drag to reach space and still retain sufficient velocity to attain orbit.

To attain that kind of velocity using a catapult of any realistic length will require greater than 3g's.

If you are launching a ramjet (how functional are they are very high altitudes?) or other vehicle that can generate its own thrust, or else if there is no limit on the proposed size of the catapult, then I agree the problem is not so daunting.

Faultline
2005-Jul-28, 06:53 PM
Keep in mind that the purpose of a launch catapult would be to make a less costly and more efficient way of getting something into orbit.

Keep in mind also that there would be limits imposed on the size of such a catapult and it would be exponentially more costly than airport runway tarmac.

Keep in mind also the eletrical power requirements of such a system. Just because we can plug in a lamp and get light doesn't mean it costs us pennies. The electricity has to come from somwhere, and might be in the gigawatt range for a single launching.

True, I'm speculating since I don't know enough about electricity and electromagnets to calculate the power needs. But SOMETHING has to be burned to produce that power, otherwise it needs a couple dozen 1,000 megawatt nuclear power plants to provide it with electricity.

Am I off? Am I too high on my estimates of power requirements for a 200-300 kilometer long e-mag mass driver?

Someone crunch numbers, please.

Faultline

Faultline
2005-Jul-28, 06:57 PM
8-[

Little Boy:
Mr. Owl, how many spent rocket cartridges does it take to equal the cost of building a 300 kilometer long mass driver and the nuclear power plant to supply it?

Mr. Owl:
Let's find out...

PatKelley
2005-Jul-28, 07:18 PM
8-[

Little Boy:
Mr. Owl, how many spent rocket cartridges does it take to equal the cost of building a 300 kilometer long mass driver and the nuclear power plant to supply it?

Mr. Owl:
Let's find out...

The utility of a linear coil-gun catapult would be not just in reusability but rapid reusability. If prep-work consists of getting the cargo into an appropriate container, and launch conditions can be extended into areas now deemed dangerous, the time-to-launch can be reduced, and the window in which objects can be put to orbit can be expanded. Reusable rockets require a retrieval and reoutfitting period, expendable rockets depend upon manufacturing times and costs and an extended logistics train.

There are pros and cons to each argument; and it would not be prudent to wholly abandon either, as they each offere differing advantages. For instance, for human spaceflight an early model coil-launch system would probably be unlikely. Cost was apparently an objection overcome in the Apollo program.

Faultline
2005-Jul-28, 08:48 PM
And another thing to consider: Aiming.

How the heck do you aim something longer than a dozen Sears Towers and heavier than the US Naval fleet?


Not everything that enters orbit enters into the same trajectory. If you couldn't design a carriage that could both rotate and elevate the monster, you'd be limited to controlling the speed of orbital insertion and that would restrict its usefulness.

I'm considering the suggested lengths of 100 to 300 kilometers that have been suggested. Size versus g-forces becomes a battle.

You make it bigger to reduce the g-forces to tolerable levels, but making it bigger reduces its usefulness and efficiency by requiring extreme feats of engineering and huge amounts of power.

A small, efficient design would reduce electronics to powder, while a big one becomes unwieldy.

And I'm still waiting on an electricity genius to estimate the power requirements of a string of electromagnets 100 to 300 kilometers long that are capable of accelerating an object to... (KPH = orbital velocity plus an extra amount needed to overcome air resistance and gravity)...

Also, would an e-mag pulse of that power level fry electronics? Protecting it would add weight. Preparation and creation of the satellite would require making sure none of its metal, ferrous components would be damaged by strong magnetic fields.

Oh heck. Just hire Magneto to do the job!

Faultline

Jpax2003
2005-Jul-28, 08:58 PM
Aiming? Are you serious? As long as the catapult points in a direction above the horizon the proper amount of velocity will take it to space. If you need to place it into a specific orbit, then wait until the earth rotates into position for launch. If you need to tweak the orbit, then the payload can have small thrusters for that.

Faultline
2005-Jul-28, 09:13 PM
Aiming? Are you serious? As long as the catapult points in a direction above the horizon the proper amount of velocity will take it to space. If you need to place it into a specific orbit, then wait until the earth rotates into position for launch. If you need to tweak the orbit, then the payload can have small thrusters for that.

Sure I'm serious. With a fixed mount, even with Earth rotation (it only goes one direction, one path, one big circle) and variable launch speed, you're limited in the type and angle of your orbital trajectory. There are bound to be a number of orbits that small tweaking won't get to.

But you're right, it's less of a problem than I thought at first. Still, an issue that limits it.

Still you have to contend with the effects of strong e-mags on electronics, hardening the satellite not only against g-forces but against the EMP adds considerable weight (ANY weight is considerable when talking orbital launches), and power requirements.

Any number crunchers want to estimate power requirements?

Faultline

formulaterp
2005-Jul-28, 10:15 PM
Aiming? Are you serious? As long as the catapult points in a direction above the horizon the proper amount of velocity will take it to space. If you need to place it into a specific orbit, then wait until the earth rotates into position for launch. If you need to tweak the orbit, then the payload can have small thrusters for that.

Let's say the catapult is built exactly on the equator running West to East. How exactly do you get your payload to a 51 degree inclination to deliver something to the ISS? That's a pretty big plane change you're requiring from a couple of small thrusters.


The utility of a linear coil-gun catapult would be not just in reusability but rapid reusability ... Reusable rockets require a retrieval and reoutfitting period, expendable rockets depend upon manufacturing times and costs and an extended logistics train.

Rapid reusability is absolutely no concern whatsoever for the satellite launching industry. It never has been, and it likely won't be in the foreseeble future. Lockheed, Boeing, Arianespace, RKK-Energia and others would be more than happy to launch at 2-3 times the current frequency. Unfortunately there's just nothing to launch.

Jorge
2005-Jul-28, 10:25 PM
well, if you can lauch lets say 15 small packets into orbit, it could be usefull for seding materials up there to build a big spacehsip in space, or a bigger space station for example.

Faultline
2005-Jul-28, 11:13 PM
well, if you can lauch lets say 15 small packets into orbit, it could be usefull for seding materials up there to build a big spacehsip in space, or a bigger space station for example.

Unfortunately, most things are more complicated than they seem in discussion.

Brute force rockets are the best and most efficient way for getting payloads into space. As powerful as the space shuttle is, and as fast as it flies, its biggest limitation is the altitude it can reach (someone quote the highest space shuttle flight for me :) ).

Altitude? That's right. In fact, a catapult would have to accelerate its payload to even MORE ridiculous speeds in order to reach geosynch orbit, which is pretty high indeed. Rocket engines are the best at this. (Someone can quote geosynch altitude for me, I'm sure).

And if you want to, say, launch it as far as you can get it with a catapult then let rockets carry it the rest of the way to geosynch, there's another problem. The weight of the rocket fuel would increase the amount of power needed to heft such a load into orbit.

At least a rocket gets lighter as it ascends!

Faultline

Jpax2003
2005-Jul-29, 12:16 AM
Let's say the catapult is built exactly on the equator running West to East. How exactly do you get your payload to a 51 degree inclination to deliver something to the ISS? That's a pretty big plane change you're requiring from a couple of small thrusters.

Rocket. You don't seriously think the length of a long coilgun can be moved and maneuvered, do you? So no, aiming is a non-issue. Any orbit that can't be reached by coilgun ejection is not suitable for launch by a coilgun. That would seem obvious.


Rapid reusability is absolutely no concern whatsoever for the satellite launching industry. It never has been, and it likely won't be in the foreseeble future. Lockheed, Boeing, Arianespace, RKK-Energia and others would be more than happy to launch at 2-3 times the current frequency. Unfortunately there's just nothing to launch.

There probably won't be much to launch while launch prices are so high. but you are right that it's not a matter of rapid re-usability as it is a matter of rapid usability. I think that the more often we can launch a payload for low cost the more often we would find something worth launching.

Jorge
2005-Jul-29, 03:24 PM
also if the cost is low, we might see more ameture(spelling is wrong i know) projects.

Jpax2003
2005-Jul-29, 07:04 PM
also if the cost is low, we might see more ameture(spelling is wrong i know) projects.

amateur

Faultline
2005-Aug-02, 12:26 AM
My backyard version of this thing cost me $1.3 billion to build and it's under a 1/4 mile long.

The highest I've ever launched a 50-ton payload is a short 20 miles above the Earth.

It needs tweaking, because the watermelon inside the capsule got smushed into a fine paste that I think I'll try to sell to Lyle Lovett as hair gel, watermelon scented.

Plus, my neighbors are complaining about the sonic booms.

It weighs less than I thought. Nuclear Power Plant, capacitors, carriage and all weigh in at 1,752 tons.

I need help from the community. Help me request that Congress allocate $9 billion to operate it for the next ten years, plus $254,329.22 for shockwave-proof windows in my home town.

:D :D :D
Faultline

PatKelley
2005-Aug-02, 12:33 AM
My backyard version of this thing cost me $1.3 billion to build and it's under a 1/4 mile long.

The highest I've ever launched a 50-ton payload is a short 20 miles above the Earth.

It needs tweaking, because the watermelon inside the capsule got smushed into a fine paste that I think I'll try to sell to Lyle Lovett as hair gel, watermelon scented.

Plus, my neighbors are complaining about the sonic booms.

It weighs less than I thought. Nuclear Power Plant, capacitors, carriage and all weigh in at 1,752 tons.

I need help from the community. Help me request that Congress allocate $9 billion to operate it for the next ten years, plus $254,329.22 for shockwave-proof windows in my home town.

:D :D :D
Faultline

I know this is silly and all- but how many people live close enough to Cape Canaveral to have their homes incinerated at every launch? Why would anyone live close enough to a supersonic aircraft airport to have their windows shattered by the overpressure? Why do you limit it to 1/4 mile, and just where are you sending watermelons that is 20 miles up and needs 50 tons per shipment?

Jorge
2005-Aug-02, 12:33 AM
you forgot the ask money for the payload that will be used for testing,

100 tons of gold seems a good payload to test 8)

we'll split it once the launch fauled

Faultline
2005-Aug-02, 12:51 AM
I know this is silly and all- but how many people live close enough to Cape Canaveral to have their homes incinerated at every launch? Why would anyone live close enough to a supersonic aircraft airport to have their windows shattered by the overpressure? Why do you limit it to 1/4 mile, and just where are you sending watermelons that is 20 miles up and needs 50 tons per shipment?

It's sillier than you know, Pat. It's sillier now that you've challenged my parody!

Rule number 5,331 in my book is never challenge a parody. You'll just be ridiculed.

But anyway, I built it in my backyard and my neighbors thought it was going to be a ski-lift.

I limited it to a 1/4 mile long because I'm afraid of heights. Plus, I had a lack of electrical wire. Mayer Electrical Supply and Home Depot only had about 8,000 miles of copper wire on hand of a quality that I could use to make good electromagnets.

And do you know how long it takes me to get 1.3 billion from Congress? They said something about taxpayers thinking it was a dumb idea, but I told them all about how Elvis Presley said to me "Build it, and they will come" in a dream and that pushed them over the edge.

Watermelons? I only put a watermelon in the capsule to test the g-forces. I was going to use the neighbor's pit bull, but I couldn't catch him.

Plus, this is only a test. Come up with something 250 times longer and try to get funding. I think it will take more than The King to convince them. But be sure to have a plan for funding over the next ten years just in case.

Never mind if it saves enough money to pay for itself, just get creative!

Faultline :P :P :P

PatKelley
2005-Aug-02, 01:24 AM
I see. Being dismissive of the idea is easy I suppose when bias exists agianst it in the first place.

Contemporary criticism of Goddard

Goddard was suspicious of others and often worked alone, which limited the ripple effect from his work. His unsociability was a result of the harsh criticism that he received from the media and from other scientists, who doubted the viability of rocket travel in space. After one of his experiments in 1929, a local Worcester newspaper carried the headline "Moon rocket misses target by 238,799 1/2 miles."

Most notable however was the, retrospectively funny, response of The New York Times to Goddard's landmark 1919 paper, "A Method of Reaching Extreme Altitudes." The Times lambasted his research because "everybody knows" rockets won't travel in the vacuum of space, where there's nothing to push against. Goddard, the article claimed, "seems to lack the knowledge ladled out daily in high schools."

link (http://www.answers.com/topic/robert-goddard)

formulaterp
2005-Aug-02, 02:09 AM
Yes, yes, they laughed at Goddard.
They laughed at Einstein.
They laughed at Galileo.
They laughed at Bozo the Clown.

Occasionally they're right. Some things are just silly.

PatKelley
2005-Aug-02, 02:11 AM
However, this is not a new idea.
Particle accelerators use similar technology and are already funded for rather large areas to the tune of millions of dollars with payloads measured in electron-volts.
It is not my own idea, and my only comparison in doing so was saying that parody does not invalidate the idea, as the technology exists and the only thing lacking is serious pursuit. In this the two are quite similar.

Even accelerations of 10,000 to 30,000 g's were apparently sustainable by some electronic payloads...
HARP and gun-launched sub-orbital probes. (http://www.dunnspace.com/harp.htm)

Faultline
2005-Aug-02, 08:05 PM
However, this is not a new idea.
Particle accelerators use similar technology and are already funded for rather large areas to the tune of millions of dollars with payloads measured in electron-volts.
It is not my own idea, and my only comparison in doing so was saying that parody does not invalidate the idea, as the technology exists and the only thing lacking is serious pursuit. In this the two are quite similar.

Even accelerations of 10,000 to 30,000 g's were apparently sustainable by some electronic payloads...
HARP and gun-launched sub-orbital probes. (http://www.dunnspace.com/harp.htm)

I read the article and missed where it said electronics could sustain 30,000 g's. I can't imagine a 1 ounce computer chip working properly after it gets jabbed by anywhere from 600 pounds to 1 ton. (Multiplying it's weight by the g-forces).

And this was all acheived with rockets using a gun to assist in the launch. It still had only 40 pounds of payload and 1960 pounds of reaction mass. That's 98% wasteful. How much better is that than current rockets?

I think someone looked at the numbers and said, "Pull the plug."

Faultline

Manchurian Taikonaut
2005-Aug-02, 08:09 PM
Cannon-shot, Catapult payloads some are talking about would cause the objects to burn-up from friction long before they reached orbit

Sock Munkey
2005-Aug-02, 08:31 PM
I think laser propulsion is our best option for reaching orbit. All the advantages of an EM launcher without the harsh acceleration.

Faultline
2005-Aug-02, 08:41 PM
Cannon-shot, Catapult payloads some are talking about would cause the objects to burn-up from friction long before they reached orbit

First, it's not friction that causes heat from extreme velocity in atmosphere. It's compression. The air can't get out of the way fast enough because of the object's velocity and gets compressed. Compressed gasses heat up.

What friction DOES cause is a loss of velocity, which means the initial velocity has to be MUCH higher in order to reach even a low orbit.

Not that I'm for the idea of a cannon-launched satellite, but we could make a capsule to hold and protect a satellite that can resist the heat from more than 9 kilometers (plus velocity needed to overcome friction loss) a second in atmophere.

It just means more weight and less payload, just like rocket fuel.

Faultline

formulaterp
2005-Aug-02, 08:50 PM
I think laser propulsion is our best option for reaching orbit. All the advantages of an EM launcher without the harsh acceleration.

I think you might find that laser propulsion has a couple of technical hurdles as well.

I just have a hard time understanding why rockets are such a bad idea. If rockets are too expensive, ... build ... cheaper ... rockets.

I know what you're thinking, easier said than done. Wanna a quick and dirty solution to chop a few bucks off the price of a Delta IV or Atlas V? Take the blueprints for the factory and tooling and set up shop in India or China. How much money would you save? Why not start with a cheaper rocket like Proton or Soyuz and do the same?

Government red tape aside, isn't this a bit more feasible than a 600km long railgun?

PatKelley
2005-Aug-02, 08:56 PM
I think laser propulsion is our best option for reaching orbit. All the advantages of an EM launcher without the harsh acceleration.

I think you might find that laser propulsion has a couple of technical hurdles as well.

I just have a hard time understanding why rockets are such a bad idea. If rockets are too expensive, ... build ... cheaper ... rockets.

I know what you're thinking, easier said than done. Wanna a quick and dirty solution to chop a few bucks off the price of a Delta IV or Atlas V? Take the blueprints for the factory and tooling and set up shop in India or China. How much money would you save? Why not start with a cheaper rocket like Proton or Soyuz and do the same?

Government red tape aside, isn't this a bit more feasible than a 600km long railgun?

Depends upon how much you intend to use each. Disposable resources have to be balanced against duration of use; consider how long we intend to be going into space: will it stop anytime soon? Is there a reason we spend money on disposable resources rather than creating a completely reusable launch system?

formulaterp
2005-Aug-02, 09:12 PM
Is there a reason we spend money on disposable resources rather than creating a completely reusable launch system?

I'm gonna take a wild guess and say that the only reusable launch system we've ever developed actually costs more than the disposable alternatives.

And it's not like rockets are necessarily disposable. Look at the SRB. Something as simple as a parachute, and voila! Reusability. (OK, not quite that simple :wink: ) No scramjets, no railguns, no giant lasers needed. Oh and they work.

PatKelley
2005-Aug-02, 09:19 PM
Is there a reason we spend money on disposable resources rather than creating a completely reusable launch system?

I'm gonna take a wild guess and say that the only reusable launch system we've ever developed actually costs more than the disposable alternatives.

And it's not like rockets are necessarily disposable. Look at the SRB. Something as simple as a parachute, and voila! Reusability. (OK, not quite that simple :wink: ) No scramjets, no railguns, no giant lasers needed. Oh and they work.

(Bolding mine) The sniping isn't necessary; I'm not assaulting rocketry or necessarily pushing alternatives. There are benefits in mass production of disposable rockets, in that eventually most of the kinks can be worked out. However, the long-term goal appears to be to reduce cost-to-orbit, and eventually develop a market lucrative enough to help reduce production costs through volume. It's a catch-22: to have low-cost-to-orbit, one needs to mass produce rockets; to mass produce rockets, one needs low cost-to-orbit to increase demand and justify mass production.

My question is why not a reusable system (regardless of origin) which has a fast turnaround time and shorter logistics trail? The Delta Clipper (single stage to orbit) was a good idea which might fare better given the current climate.

Jorge
2005-Aug-02, 11:05 PM
well, cheaper rockets could work...
maybe we need to make a new fuel mix that is more efficient.

Then again a huge railgun/Catapult is so much cooler

Faultline
2005-Aug-02, 11:31 PM
I don't imagine I'll settle this idea for the believers, but I'm going to have my final say and then (barring any flames) I'll be through with this thread.


All we can do is speculate. But so far, the speculation doesn't look favorable. I'd vote that launching something into orbit without reaction mass isn't viable because of the extra velocity needed to overcome air friction, and because of the size of the thing needed to reduce g-forces to managable levels would make it expensive and impossible to aim at more than a few simple orbits.

Expenses wouldn't end with its creation either. Like any "reusable" item, it would need crews for maintenance and replacement parts for both it's capacitors, it's rails, it's aiming system, it's power source. That's why I joked at needing $9 billion for 10 years. It's probably a fraction of what a 300 or 600km long unit would cost to maintain when you count teams of engineers and scientists and repair people working all the time on such a complex object.

Think about the crew (and security teams) a nuclear power plant needs. You'd need nuclear power to feed the thing!

Then, you'd still need regular rockets to get things into geosynch orbit, which I learned isn't 200 or 400 miles up, its... 24,300 miles up! Jeez! What kind of acceleration would you need for that?

And then, payload size hasn't really been discussed. If you want it to be rocket-assisted, you need to subtract from payload and add fuel. Then it needs a heat shield to withstand its own orbital velocity while leaving the atmosphere. That reduces payload, also.

Sure, we can put an artillery shell into orbit, but what happens when you want to put a 10 ton satellite up to a usable altitude of 300 miles? You're talking huge acceleration, huge EMP from the cannon, huge amounts of power, huge amounts of air friction to be overcome, super-tough electronics that can take not only the acceleration, but the magnetics that could fry them. The extra hardening and shielding both add weight and subtract from payload.

Until someone can tell us how big it would have to be, how much it would cost, and how much power it would require, and how much it would cost to maintain, and how much payload it could get to what altitude, I'm afraid I won't believe any such thing is practical.

Oh, my parody was based on some version of reality, too.

Ever hear of GURPS? It includes a system for designing e-mag cannons and I used it to make the biggest thing I could. The system is based in solid principles.

The thing was less than a quarter mile in length, had an aiming carriage that weighed as much as it did.

Even with generous estimates, I couldn't get the math to work. 20 miles was maximum altitude and the thing needed power like you wouldn't believe.

Try this for those who know GURPS design rules:
1800mm Electromagnetic Cannon TL/8
Extremely Long Barrel Low Power
Breechloader
Super Fine Quality
Plus, a TL/8 Nuclear Power Unit and enough TL/8 Power Cells to charge for 1 full power shot every two hours.
A Universal Casemate Mount

I considered removing the "Low Power" restriction, but I'm in Alabama and I don't think that Georgia would like that very much. 8) :D

Faultline

PatKelley
2005-Aug-02, 11:43 PM
HAHAHA! You used GURPS to design your gauss-cannon? :)
Glad to see another RPG'r is on the forums...

I managed to dredge up a proposal for a one-mile linear accelerator (particle) and associated projected costs on a 170 acre compound, as comparison with accelerators with bending magnets would not be appropriate :


According to information provided by DOE, the particle accelerator under consideration would be one mile long and part of a 170-acre complex. The proposed plant would be similar in some respects to the continuous electron beam accelerator facility (CEBAF) at the Thomas Jefferson National Accelerator Facility (the Jefferson Lab) in Newport News, Virginia, and the linear accelerator at the Los Alamos Neutron Science Center. The machine would require about 450 megawatts (MW) of power to deliver a high-power proton beam at 100 MW. That would be about two orders of magnitude greater than existing research accelerators, such as the one at Jefferson Lab. In addition to building the accelerator and related buildings at the Savannah River site, DOE would upgrade the existing tritium-recycling facilities there to support the accelerator plant. Assuming all went as planned, the plant would deliver the first tritium by 2008 and operate for 40 years. CBO estimates that construction and 40 years of operation would cost a total of $9.5 billion in 1999 dollars (see Table 1).
Link (http://www.cbo.gov/showdoc.cfm?index=831&sequence=0)


So construction, estimated at about 6 billion costed over a forty-year bond, means operation costs over forty years are projected at 3 billion.

As a comparison of power usage, the "Tower of Terror" (http://www.ride-extravaganza.com/rides/tower_of_terror/)which uses linear accelerators on a rail, uses 2.2 Megawatts over eight seconds to reach 160 km/h. With an available 450 Megawatts, it might be possible to accelerate a payload to orbital speeds.

publiusr
2005-Aug-03, 07:46 PM
Is there a reason we spend money on disposable resources rather than creating a completely reusable launch system?

I'm gonna take a wild guess and say that the only reusable launch system we've ever developed actually costs more than the disposable alternatives.

And it's not like rockets are necessarily disposable. Look at the SRB. Something as simple as a parachute, and voila! Reusability. (OK, not quite that simple :wink: ) No scramjets, no railguns, no giant lasers needed. Oh and they work.

Bingo! Beats a massive laser projector hooked to a nuclear pile a mile on a side. If its stout enought to (barely) put, say, A Soyuz capsule in LEO...

Its powerful enough to vaporize it on the way up.

Jorge
2005-Aug-03, 09:47 PM
Alternatively we can get a few poeple up there and start a breading program to replenish the crew 8) ...

well that is if humans can develop in space

Faultline
2005-Aug-04, 10:02 PM
HAHAHA! You used GURPS to design your gauss-cannon? :)
Glad to see another RPG'r is on the forums...

I managed to dredge up a proposal for a one-mile linear accelerator (particle) and associated projected costs on a 170 acre compound, as comparison with accelerators with bending magnets would not be appropriate :


According to information provided by DOE, the particle accelerator under consideration would be one mile long and part of a 170-acre complex. The proposed plant would be similar in some respects to the continuous electron beam accelerator facility (CEBAF) at the Thomas Jefferson National Accelerator Facility (the Jefferson Lab) in Newport News, Virginia, and the linear accelerator at the Los Alamos Neutron Science Center. The machine would require about 450 megawatts (MW) of power to deliver a high-power proton beam at 100 MW. That would be about two orders of magnitude greater than existing research accelerators, such as the one at Jefferson Lab. In addition to building the accelerator and related buildings at the Savannah River site, DOE would upgrade the existing tritium-recycling facilities there to support the accelerator plant. Assuming all went as planned, the plant would deliver the first tritium by 2008 and operate for 40 years. CBO estimates that construction and 40 years of operation would cost a total of $9.5 billion in 1999 dollars (see Table 1).
Link (http://www.cbo.gov/showdoc.cfm?index=831&sequence=0)


So construction, estimated at about 6 billion costed over a forty-year bond, means operation costs over forty years are projected at 3 billion.

As a comparison of power usage, the "Tower of Terror" (http://www.ride-extravaganza.com/rides/tower_of_terror/)which uses linear accelerators on a rail, uses 2.2 Megawatts over eight seconds to reach 160 km/h. With an available 450 Megawatts, it might be possible to accelerate a payload to orbital speeds.

450 MW won't cut it. If it takes 2.2 MW over 6 seconds to accelerate a 6 ton payload to 160 KPH, then 450 MW would (just using linear math, nothing fancy) get 6 tons moving at around 32,000 KPH. That's enough velocity to poke your nose into space and fall down by the time gravity and air resistance has its way.

Plus, we really need more than 6 tons. It's not much compared to the Space Shuttle's 17 tons.

[-(

Ara Pacis
2005-Aug-04, 11:21 PM
Plus, we really need more than 6 tons. It's not much compared to the Space Shuttle's 17 tons.

>1/3 payload with the advantage of quicker turnaround and lower maintenance costs per cycle.

Faultline
2005-Aug-05, 02:54 AM
Plus, we really need more than 6 tons. It's not much compared to the Space Shuttle's 17 tons.

>1/3 payload with the advantage of quicker turnaround and lower maintenance costs per cycle.

You might have missed the part where I said that 450 MW proposed by Patkelly wasn't enough to get 6 tons moving at (orbitalvelocity+velocity needed to overcome friction and still reach your target orbit).

Plus, even if you could get it to launch 6 tons, what good is a 6 ton payload if typical payloads are in the 10+ ton range?

Keep in mind other things that limit your ACTUAL payload size. To shoot something from a cannon you'd need to make it aerodynamically capable of breaking the sound barrier without shredding itself. That means making it look like a dart for flight stability. That subtracts from ACTUAL payload.

Then, it needs to be heat-resistant. It needs an outer shell on that aerodynamic casing that can take the heat. That, again, subtracts from ACTUAL payload.

Plus, the extra hardening needed for the g-forces of acceleration (assuming you want a smaller, more compact design for the launcher that can be aimed and isn't at the mercy of the Earth's position in rotation) will add weight and subtract from ACTUAL payload.

Then you have to make sure the electronics are tough enough and shielded enough versus the EMP produced by this 450+ MW string of electromagnets. That subtracts from ACTUAL payload.

Then, if you want to reach a higher orbit (or for a gargantuan, non-aimable version of this cannon), you need to have rockets on the thing for maneuvering or boosting. And that.... well, I won't say it again. You get the picture.

So if 450 MW can't get 6 tons into space and your 6 tons has to include all of the above, you're not getting a tradeoff.

Someone tell me how much power you need to electromagnetically sling an 18 ton payload up to low earth orbit! THAT will tell you if this thing can be made more efficient than the space shuttle!

This does not change the fact that we need a heavy orbital lifter to get things into higher orbits, even geosynch which is 24,300 miles up!

Ara Pacis
2005-Aug-05, 04:08 AM
Faultline, you may be correct, but how does all that disprove my points that a coilgun should have quicker turn-around time and lower maintenance costs per cycle?

PatKelley
2005-Aug-05, 05:50 AM
450 MW won't cut it. If it takes 2.2 MW over 6 seconds to accelerate a 6 ton payload to 160 KPH, then 450 MW would (just using linear math, nothing fancy) get 6 tons moving at around 32,000 KPH. That's enough velocity to poke your nose into space and fall down by the time gravity and air resistance has its way.

Plus, we really need more than 6 tons. It's not much compared to the Space Shuttle's 17 tons.

[-(

It's really .06 Mw per ton accelerated by a rough rate of 22m/second/second

Roughly.

Over the distance of a mile, and with more added Mw per ton over a longer duration...

And for notes:

Drag has the effect of consuming about 1500 to 2000 feet per second of the rocket's velocity.

The result of all this is that a first cut analysis shows that to achieve orbit, a rocket needs about 30,000 feet per second total velocity. It won't ever go that fast, because gravity and drag will have consumed some 5,000 feet per second, but your engines have to add that much energy to the vehicle.

Rockets don't burn up in the atmosphere, at least not on launch, mainly because of direction, angle, and cross-section. So, similar to rocketry, an extra 5000 feet per second needs to be factored in.

Faultline
2005-Aug-05, 09:45 PM
Faultline, you may be correct, but how does all that disprove my points that a coilgun should have quicker turn-around time and lower maintenance costs per cycle?

A 6-ton payload is too small when you have to take out for a heat shield and extra hardening and EMP shielding. That's my point.

Rockets don't burn up on launch because they don't START OUT at 30,000 feet per second! They work their way into thinner air, gradually accelerating until the wind resistance is low enough.

And mountain tops don't thin the air enough to make a difference, otherwise climbers of Mt. Everest couldn't breathe up there.

Ara Pacis
2005-Aug-05, 10:46 PM
And mountain tops don't thin the air enough to make a difference, otherwise climbers of Mt. Everest couldn't breathe up there.

The summit of Everest is above the Death Zone (http://en.wikipedia.org/wiki/Death_zone). While the availablility of oxygen is important for human physiology you have not stated how the density of all atmospheric gasses at this altitude would affect hypersonic transits of ballistic vehicles. In other words, your statement is a strawman fallacy.

DoktorGreg
2005-Aug-05, 10:48 PM
Im surprised no one here mentioned it. It is a pre-internet thing, so i have had trouble finding good google references to it, but...

Saddam Hussein was building a giant cannon prior to Bush War I that was capable of throwing a couple thousand pounds into space. As the Cannon was capable of throwing ordinance, it would seem like you could put a rocket in there, coast from the initial blast into space, then fire an orbital rocket to get to orbital velocity.

Or...

Park a skyhook in an orbit over the cannon, and catch the payload as it goes by.

Or...

Just scale the thing up to throw 100,000 lbs. things into orbit, rather than 2,000 lbs. things.

montebianco
2005-Aug-05, 10:59 PM
And mountain tops don't thin the air enough to make a difference, otherwise climbers of Mt. Everest couldn't breathe up there.

The summit of Everest is above the Death Zone (http://en.wikipedia.org/wiki/Death_zone). While the availablility of oxygen is important for human physiology you have not stated how the density of all atmospheric gasses at this altitude would affect hypersonic transits of ballistic vehicles. In other words, your statement is a strawman fallacy.

As the article states, atmospheric pressure on top of Mt. Everest is about 1/3 that at sea level. If air is a problem, it seems like reducing it by 2/3 ought to make a difference...

Ara Pacis
2005-Aug-05, 11:22 PM
As the article states, atmospheric pressure on top of Mt. Everest is about 1/3 that at sea level. If air is a problem, it seems like reducing it by 2/3 ought to make a difference...

I agree, putting it on a mountain would help. Does anyone have a graph showing the velocity of the STS or other rockets at that altitude? I looked but couldn't find one.


DocktorGreg, The man who was building the supergun was Gerald Bull (http://en.wikipedia.org/wiki/Gerald_Bull). Wikipedia has several articles about him, the Project Babylon Supergun, and Project Harp.

Launch window
2005-Aug-05, 11:39 PM
No it is not possible
the only way you'll do this trebuchet Catapult to space is in some children's little dream

Sorry guys, but the physics for this one are just way off

montebianco
2005-Aug-06, 12:38 AM
As the article states, atmospheric pressure on top of Mt. Everest is about 1/3 that at sea level. If air is a problem, it seems like reducing it by 2/3 ought to make a difference...

I agree, putting it on a mountain would help. Does anyone have a graph showing the velocity of the STS or other rockets at that altitude? I looked but couldn't find one.

No graph, but if a rocket flies from sea level straight up at a constant rate of acceleration, I'm getting that it's velocity at the height of Mt. Everest should be about 1360 ft/s times the square root of the number of Gs. In metric, that would be 415 m/s, or if you prefer, 930 miles/hr or 1500 km/hr.

Answering the question because it was asked, I'm not a big believer in this concept, and construction on the top of Mt. Everest seems rather less than feasible for a number of reasons...

PatKelley
2005-Aug-06, 01:45 AM
It is not a question of belief: it is a question of whether the physics is plausable, and if so, whether or not the construction dimensions are feasable, and fiscally attainable.

The military has already invested in coil-gun based technology, partly because railguns destroyed themselves through oscillations in the sled by firing two or three. Projected muzzle-velocities for combat were six miles per second, obviating armor and by extension manned combat vehicles.


Linear motors have not been pursued to anywhere near a comparable degree, although an appreciable literature exists. Linear motors might be on the threshhold of an evolution comparable to the evolution of rotary motors. The above survey indicates that there is no shortage of new concepts or uses. What makes this field exciting is the advent of new pulsed energy sources, and the challenging fact that a motor of zero curvature is virtually free of all fundamental limitations on size, acceleration and velocity.

Source (http://www.oz.net/~coilgun/theory/electroguns.htm)

From this gentleman's account (http://www.powerlabs.org/railgun2.htm) of his own successes, the military is still interested in this region of research, although railguns are, in my mind, still something of a more difficult technology than coilguns.

From a cached DARPA request for proposals website...


The Electro-Magnetic (EM) Mortar program will design and demonstrate EM guns (coilgun and railgun) capable of firing modified 120 mm mortar rounds to 420 m/s. The second goal is to evaluate significant system “trade space issues” for implementation including: 1) Ammunition integration and compatibility; 2) Vehicle integration concerns; 3) System reliability metrics (Barrel life, EM Interference); 4) Lethality change due to modification; and 5) System supportability metrics.

EM Mortar

* Conduct modeling and simulation to design the launcher, power supply, and projectile modifications for coupling to the launcher.
* Design launcher for mortar launch application and develop specifications for the power system coil and rail guns.
* Fabricate coil and rail gun launchers.
* Conduct laboratory testing of the launchers with capacitor-based power systems.
* Assess large-scale manufacturing issues for capacitors and demonstrate operation in a full-size module.
* Conduct ammunition and weapon system testing.



Edited to add: check this out at the TTO office of DARPA:
Infantry Robots (http://www.arpa.mil/baa/baa05-22.htm) are mentioned after unmanned combat vehicles in section 2 point f in "AREAS OF INTEREST"

montebianco
2005-Aug-06, 03:43 AM
It is not a question of belief:

I think the meaning of my statement is quite clear.

Faultline
2005-Aug-06, 04:40 AM
And mountain tops don't thin the air enough to make a difference, otherwise climbers of Mt. Everest couldn't breathe up there.

The summit of Everest is above the Death Zone (http://en.wikipedia.org/wiki/Death_zone). While the availablility of oxygen is important for human physiology you have not stated how the density of all atmospheric gasses at this altitude would affect hypersonic transits of ballistic vehicles. In other words, your statement is a strawman fallacy.

Okay, humans can't breathe for extended periods at that level because of a lack of oxygen. But planes fly regularly higher than 10,000 meters. While their pilots require pressurized cabins, obviously the atmosphere isn't so thin that the airfoil of their wings won't allow flight.


The atmosphere has no abrupt cut-off. It slowly becomes thinner and fades away into space. There is no definite boundary between the atmosphere and outer space. Three-quarters of the atmosphere's mass is within 11 km of the planetary surface. In the United States, persons who travel above an altitude of 50.0 miles (80.5 km) are designated as astronauts. An altitude of 120 km (75 mi or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Karman line, at 100 km (62 mi), is also frequently used as the boundary between atmosphere and space.

The above is also from Wikipedia. According to this, 3/4 of the mass of the atmosphere is below 11km altitude. Even at Mount Everest height, you still have a lot of air to plow through.

And the supergun was a legend. I read the Wikipedia article on Project Babylon. Though construction began, it was never completed and only rumored to be able to reach orbit. It's easy to rumor something, but rumors aren't fact. My personal opinion was that Saddam wanted a way to lob a WMD to Israel, not to put a sattelite into orbit.

What would Iraq do with a 2,000 pound sattelite? Their air force was so outdated that he didn't send any of them up to challenge ours in either war!

As for PatKelly's DARPA data, I'm sure that electromagnets would make good weapons by firing little projectiles at high speeds someday when storage of electrical power becomes more size efficient and other bugs are smashed out of the system. It's just not practical for orbital launch of vehicles or sattelites of STS payload weight that contain electronics.

Maybe someday you could use one to hurl chunks of metal into low earth orbit where a shuttle could take them to be processed into bulk parts by an orbital foundry. Just be prepared to lose some material on the way up.

PatKelley
2005-Aug-06, 03:20 PM
My point was that linear accelerators have been built. Power needs up to 450 Mw have been addressed. Technology for larger than particle size is practical enough for DARPA to include it in project proposals. Coil and Railgun proposals are on the books for other government projects. Faraday cages are enough to shield electronics from magnetic and electrical disturbance, and using such a device for raw material would free up other proposals to focus on human safety without constraints driven by cargo concerns.

The heating due to atmospheric compression at sea level has been invoked as enough to burn up the cargo on launch; however, re-entry vehicles are configured to use this compression for braking and to bleed off orbital speed, not to minimize it. Objects which do burn up are not shielded, not oriented, and expressely designed to not survive re-entry. Angles of ascent have a lot to do with this as well, as re-entry paths are not perpendicular to the atmosphere for the same reason re-entry vehicles are not streamlined. Additionally, titanium components of elements destined for burn-up on re-entry have survived to the ground.

While the ultimate feasability of such a project is definitely open to question, the outright dismissal and denegration of the idea through spurious argument is not appropriate to the debate. A better way to address this is through calculations, numbers and articles, preferably in line with the discussion.

montebianco
2005-Aug-06, 04:33 PM
the outright dismissal and denegration of the idea through spurious argument is not appropriate to the debate.

If simply expressing an opinion constitutes the outright dismissal and denegration of the idea through spurious argument, you might want to take a look at some of your own posts at this board.


A better way to address this is through calculations, numbers and articles, preferably in line with the discussion.

I had numbers and calculations in line with the discussion in my posts. Maybe you didn't see them?

PatKelley
2005-Aug-06, 07:08 PM
the outright dismissal and denegration of the idea through spurious argument is not appropriate to the debate.

If simply expressing an opinion constitutes the outright dismissal and denegration of the idea through spurious argument, you might want to take a look at some of your own posts at this board.


A better way to address this is through calculations, numbers and articles, preferably in line with the discussion.

I had numbers and calculations in line with the discussion in my posts. Maybe you didn't see them?

montebianco: the specifics above were addressed at Faultline's line of argument regarding the cargo instantaneously burning up in the atmosphere, and no calculations given by him: just assumptions because satellites and spent rocket stages burn up on re-entry, plus a droll comment given by Launch window:

No it is not possible
the only way you'll do this trebuchet Catapult to space is in some children's little dream

Sorry guys, but the physics for this one are just way off

I would rather folks discuss numbers and calculations rather than dismissing the idea out of hand, especially with such brief comments. When asked, I have provided estimates on required length of catapult for various G-loading, estimated possible capacity based on current capabilities, and even cost estimates for construction and operating costs considering current similar facilities.

I'll admit, to be dismissed without further reference is chafing. Especially being dismissed as a child.

montebianco
2005-Aug-06, 07:24 PM
OK, your post following mine and referring to "belief" caused me to think you were referring to me. If my subsequent comments were inappropriately based on this impression, then my apologies...

PatKelley
2005-Aug-06, 07:30 PM
OK, your post following mine and referring to "belief" caused me to think you were referring to me. If my subsequent comments were inappropriately based on this impression, then my apologies...

None necessary. With the fireworks over in BABB, I'd prefer to avoid misunderstandings and heated language myself. I'm slowly training myself to do that, but it's darn hard, and my writing style is terse in the first place. :)

Ara Pacis
2005-Aug-06, 11:39 PM
the outright dismissal and denegration of the idea through spurious argument is not appropriate to the debate.

If simply expressing an opinion constitutes the outright dismissal and denegration of the idea through spurious argument, you might want to take a look at some of your own posts at this board.


A better way to address this is through calculations, numbers and articles, preferably in line with the discussion.

I had numbers and calculations in line with the discussion in my posts. Maybe you didn't see them?

Montebianco, I think he is referring to Faultline as do I when I mention strawman fallacies and concerns for arguments based on data instead of anecdote. I appreciate you answering my question on rocket ascent velocities as I was wondering how the speeds of those vehicles compare to the projected ascent velocities of coilgun vehicles. It looks like there is a big difference at that altitude where one might place a mountain-based catapult ejection port.

For the record I am not sure that coilgun-based earth ascent is feasible now or ever. However, I do not think it is impossible either. I think it might work on the moon or even in orbit as a means of accelerating to earth escape velocities. I've also wondered if an explosive based ascent is possible using an Operation Plumbob (Pascal-B) type gun. Perhaps a mini-nuke or gamma-ray laser could vaporize rock in a vertical shaft that would push a vehicle out of the shaft with ascent to orbit or escape velocities. It might use one or more initiations to get to the proper speed (similar to Hitler's V3) and need a shock absorber on the vehicle, but it might be possible if ejected at a high elevation with proper aero dynamics.

cjl
2005-Aug-07, 12:41 AM
I believe that it could work to launch something from the moon to farther distances, but due to aerodynamic heating and drag, i believe that it would be a very implausible and ineficcient method to get off of any planet with an atmosphere.

Faultline
2005-Aug-09, 10:23 PM
So, based on the figures for the eletromagnetic thrill ride mentioned before, how many megawatts would it take to accelerate, say, 20 tons to low earth orbit?

Let's assume it takes an initial launch velocity of 50,000 kph to overcome wind resistance and gravity's deceleration.

Can we say that the payload is 17 tons (same as the shuttle)and the heat shield, aerodynamic shell, EMP shielding and hardening of electronics to take 10 or 20 g acceleration, and reaction mass for additional maneuvering all add up to a modest 3 tons (total of 20)?

Let's get rough and technical. Let's lay out some assumed numbers that we all agree are reasonable and get some calculators humming!

Look, we can all agree that the projectile will need some form of shield. Perhaps a capsule that is aerodynamic and shaped to reduce wind resistance and has heat-resistant tiles.

It needs to be hardened to resist high g forces because, let's face it, to make it useful you need every advantage you can get. An aimable launch platform is a big advantage over a fixed emplacement!

Can we figure the g-forces of accelerating to 50,000 kph over a distance of 1 kilometer? (Assuming we can aim a 1-kilometer launcher...)

Let's assume these numbers and get calculating:
Need 50,000 kph initial launch velocity to get from ground to 200 kilometer altitude while overcoming wind resistance and gravity. Safe assumption?

The payload is 17 tons (STS) and shielding capsule is 3 tons, for a total of 20 tons (18,200 kg).

How much electrical power?

What about getting 20 tons to an altitude of 24,300 kilometers (Geosynch)? What kind of velocity would you need there?

Faultline

publiusr
2005-Aug-10, 08:43 PM
That is a good question for www.liftport.com

I think they may be fooling themselves.

We need to buckle down--build rockets--and forget this pull yourself up by your bootstraps stuff.

Its just a distraction away from things we know work--much in the same way that "alt. med" types draw people away from badly needed doctor visits.

Faultline
2005-Aug-11, 05:34 AM
Maybe an e-mag catapult has one practical use on earth. Someone already mentioned this, but I forgot whom it was.

Forget reaching orbital velocity for low earth orbit. Forget big, giant launchers that are unaimable so that you cut back on g forces.

Just build a launch vehicle using scramjets. The e-mag launcher could certainly get it up to mach 2 or 3, whatever speed is needed to activate the particular model of scramjet. Then, its jets could push it to the edge of the atmosphere where a final stage could take over.

You wouldn't need nearly as much reaction mass as a ground-level rocket launch. The savings wouldn't make a tremendous difference, but it might push this idea into plausibility.

But we still need to know how much power it needs.

Faultline

publiusr
2005-Aug-11, 05:43 PM
There is a nice article in the Sept-Oct 2004 issue of AMERICAN SCIENTIST about diamagnetic levitation page 428--but you have to be careful with the clearance of just using standard magnets. Maglevs have better clearance--but permanent magnets don't need as much power.


Now if you want wild look at this space"plane"
http://www.astronautix.com/craft/naattocv.htm

And this huge saucer booster
http://www.astronautix.com/lvs/roost.htm

I suppose you could exploit the cryogenic nature of propellants and have the whole mass of the saucer levitate atop a huge magnetic 'strip.' You would accelerate it and fire rockets for a good run-and-go--and a top mount spaceplane would return to this landing strip normally.

If you spend about $100 billion.

Misc.

My writings:
http://www.xprizenews.org/index.php?p=1059

AF really in trouble now
http://www.cnn.com/2005/US/08/10/car.vandalism.ap/index.html

Nice toy for the kids:
http://www.apii.com/products.asp?idDept=17

Here is where the Xprize folks need to get their money:
http://guide.theemiratesnetwork.com/living/dubai/burj_dubai.php


Mega-lift airships
http://www.main.org/polycosmos/glxywest/aerie.htm

Huang, H., Mikyska, M. et al.: 1993, Aerotecture: The Return of the Rigid Airship, Institute of Design Communications Center, Illinois Institute of Technology, Chicago.

Also do a search for JP Aerospace for their airship concepts.