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cjackson
2011-Dec-15, 09:38 PM
If you leave Earth traveling at .01c can you reach Saturn in 6 days?

What type of presently conceptual craft could most realistically achieve this?

antoniseb
2011-Dec-15, 09:56 PM
If you leave Earth traveling at .01c can you reach Saturn in 6 days?

What type of presently conceptual craft could most realistically achieve this?

I didn't do the calculation but 6 days seems a little short. Whatever the light time of flight is times 100.
As to conceptual craft that could get a human there in six days? I think no matter what you do, the acceleration will kill you...

schlaugh
2011-Dec-15, 10:52 PM
I reckon about 3.85 days at 3000 KPS and using 1 billion kilometers to Saturn from the Earth. (divide 1 billion by 3000 [1 % of c] and you get 333,333 seconds or 92.59 hours or 3.85 days).

But as said, accelerating to that speed would be extremely fatal to anything made out of water, like humans.

ETA: For a more accurate estimate, use 1.2 billion KM for the closest distance between Earth and Saturn. About 4.6 days.

undidly
2011-Dec-16, 02:12 AM
I reckon about 3.85 days at 3000 KPS and using 1 billion kilometers to Saturn from the Earth. (divide 1 billion by 3000 [1 % of c] and you get 333,333 seconds or 92.59 hours or 3.85 days).

But as said, accelerating to that speed would be extremely fatal to anything made out of water, like humans.

ETA: For a more accurate estimate, use 1.2 billion KM for the closest distance between Earth and Saturn. About 4.6 days.

Speed is not fatal.
Acceleration can be fatal if large.
What acceleration can get a spaceship from Earth to Saturn in 4 days?

Jeff Root
2011-Dec-16, 03:09 AM
Speed can be fatal if you run into something that would be
non-fatal at a slower speed. And the higher speed can make
avoiding the thing more difficult or impossible.

Higher speed does make it less likely that you run into the
thing if you are just closing your eyes and hoping you won't
run into it...

-- Jeff, in Minneapolis

schlaugh
2011-Dec-16, 03:50 AM
My bad.

No, not fatal acceleration. Just uncomfortable.

At a constant 2g acceleration a craft could reach Saturn (1.2 billion km) in about 4.05 days.
At 1g you'd need about 5.7 days

And you'll be going really fast as you shoot past Saturn.

But...back to the OP, at 1G you'll need 3.54 days to reach 1 percent of c.

My earlier post assumed an instant start of 3000 kps. That would be fatal.

cjackson
2011-Dec-16, 04:19 AM
So 12 or more days if we want the crew to be alive? What kind of craft could do it?

undidly
2011-Dec-16, 09:14 AM
Speed can be fatal if you run into something that would be
non-fatal at a slower speed. And the higher speed can make
avoiding the thing more difficult or impossible.

Higher speed does make it less likely that you run into the
thing if you are just closing your eyes and hoping you won't
run into it...

-- Jeff, in Minneapolis

If you run into something or something runs into you it is the acceleration (to the new speed) that hurts you.
Speed is harmless.
Speed cannot even be detected by humans or measured by instruments except by external reference.

BioSci
2011-Dec-16, 05:13 PM
What kind of craft could do it?

The kind featured in science fiction.;)

antoniseb
2011-Dec-16, 05:44 PM
OK, so here's something close to what you might be thinking of ... science fiction, but no new physics...

It's a thousand years from now, and people have already established industry in the vicinity of Saturn.
There is a three million kilometer long rail launch thing on the back of the Moon going away through the Earth Moon Lagrangian point (with a few degrees of maneuverability), and the passengers breath deep-sea diving fluid, and are suspended in that fluid for launch. They accelerate the whole length of the rail at 20gs and then are in free fall for most of the rest of the trip. Near Saturn a similar rail receives the ship slowing it at 20 gs, and recaptures the energy of launch for reuse later.

This doesn't get to your 1% c, but it does get to 0.0025 c (a quarter of the speed you'd hoped for).
At 20gs, you'd need to make the rail 48 million kilometers to get up to 0.01c, and you might have some trouble avoiding Venus with the end of it.

IsaacKuo
2011-Dec-16, 07:42 PM
Or you could just go with beam propulsion. Either relativistic particle beam, or laser/microwave sail, or sailbeam could work. While a 6 day trip to Saturn would be unreasonably expensive, the beam system could be generally used for lower speed propulsion. A 6 day Saturn trip could be done for some special purpose...perhaps an expensive publicity stunt by the beam system owners.

Under normal circumstances, the microwave beam system could be used to deliver clean energy to Earth. However, demand will not precisely match supply, so there will be some excess beam capacity. This excess could be used by the energy companies for various optional activities. This could include accelerating microwave sailbots up to relativistic speeds (multi-gee acceleration of decimeter scale microwave sails has already been demonstrated in the lab by James Benford). These sailbots could then be used to accelerate and decelerate a manned spacecraft.

It's unlikely that such a high performance spacecraft would be developed specifically for a Saturn mission. More likely, it would be a step toward development of an interstellar mission.

Ilya
2011-Dec-16, 07:58 PM
My bad.

No, not fatal acceleration. Just uncomfortable.

At a constant 2g acceleration a craft could reach Saturn (1.2 billion km) in about 4.05 days.
And it will zoom by Saturn at almost 7000 km/sec.

If you accelerate halfway at 2 g then decelerate halfway, total trip time will be about 5.65 days and speed at turnover 4900 km/sec.

a1call
2011-Dec-17, 04:14 AM
Any acceleration gained by sling shots off of in-between bodies along the way will be experienced as free fall at delta 0 g.
If you don't mind crashing on the non definite surface of the gas giant then you could accelerate up-to 1.065 g (at the surface) at free fall (experiencing 0 delta g) using The giant's gravity.

Jeff Root
2011-Dec-17, 04:28 AM
I didn't follow the second part of that, a1call.
Where do you get 1.065 g? From Saturn? How?

-- Jeff, in Minneapolis

Trakar
2011-Dec-17, 04:28 AM
I didn't do the calculation but 6 days seems a little short. Whatever the light time of flight is times 100.
As to conceptual craft that could get a human there in six days? I think no matter what you do, the acceleration will kill you...

No matter what you do...?

How much leeway do you interpret into "conceptual?"

a1call
2011-Dec-17, 04:33 AM
Hi Jeff,
That's what the wiki article on Saturn says about the surface gravity. Actually I thought it would be a much higher number.

Equatorial surface gravity

10.44 m/s²[5][8]
1.065 g

http://en.wikipedia.org/wiki/Saturn

Jeff Root
2011-Dec-17, 04:48 AM
Okay. I did kinda remember that the "surface" gravity
at Saturn's cloudtops was about the same as Earth's
surface gravity, but I don't understand what you want to
do with it. Slingshot to somewhere else? That doesn't
seem to jibe with "crashing". My first guess was that
you were suggesting an alternative way to slow down
at Saturn: aerobraking in its atmosphere.

-- Jeff, in Minneapolis

a1call
2011-Dec-17, 05:02 AM
My expressive skills are not improving specially at midnight.

I was suggesting sling sooting off of Moon, Mars, and/or Jupiter experiencing free fall while accelerating and then using Saturn's gravity as an accelerator, again experiencing free fall. i was trying to make a point of all these accelerations being pain-free.

glappkaeft
2011-Dec-17, 06:04 AM
Any acceleration gained by sling shots off of in-between bodies along the way will be experienced as free fall at delta 0 g.
If you don't mind crashing on the non definite surface of the gas giant then you could accelerate up-to 1.065 g (at the surface) at free fall (experiencing 0 delta g) using The giant's gravity.

The kind of drive that can hit 0.01c (or similar) in just days makes the kind of detour required to make a sling-shot maneuver or other orbital mechanícs tricks a waste of time. It's pretty much point at you destination and shoot.

cjameshuff
2011-Dec-18, 06:32 PM
My expressive skills are not improving specially at midnight.

I was suggesting sling sooting off of Moon, Mars, and/or Jupiter experiencing free fall while accelerating and then using Saturn's gravity as an accelerator, again experiencing free fall. i was trying to make a point of all these accelerations being pain-free.

But Saturn's gravity is only ~1 g at Saturn's cloudtops, it falls off with the inverse square of distance just like that from every other body. At the distance of Earth, it's practically nothing. How is this supposed to help get you to Saturn?

Anyway, unpowered slingshot maneuvers are only good for a few tens of km/s at best. At the speeds we're talking about, they're worse than useless...the extra distance to travel will cost far more time than the tiny gain in speed saves..