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ToSeek
2003-Jul-23, 04:29 PM
Weighing the risks of human spaceflight (http://www.thespacereview.com/article/36/1)

How safe should the shuttle be?

Doodler
2003-Jul-23, 06:12 PM
Personally, I think its safe enough as it is, if an astronaut candidate cannot handle the risks of flying given the current limits of the system, wash'em out and be done with them. I liked the analogy to Everest, you make your choice to climb the mountain, you assume the risks. Both the ones you can prepare for and the ones you cannot. The best attitude to take with the shuttle is, "we did the best we could with what we were given to work with, its as good as it gets, we can't make it better until we know more". Heck, even supposedly safe, operational aricraft still have bugs that come up years down the line that designers couldn't know about, yet people still fly. I think its LONG past time to stop hand wringing already and just move on.

BigJim
2003-Jul-23, 06:56 PM
The benefits of manned spaceflight are almost infinite. But the current shuttle simply is not safe enough or capable enough. It is a vehicle which is used in the 2000s, although it is a product of 1970s technology and 1960s designs. The STS needs to be replaced with a capable and safe SSTO, like the X-33 which was cancelled two years ago. A good article can be found here. (http://www.nuclearspace.com/a_zubrin2.html) The Shuttle is a very inefficient machine because 85% of the weight it lifts is itself. It simply makes very little logistical sense. I believe the cost of flying one STS mission is comparable to that of an Apollo-Saturn IB mission, and the Saturn IB could lift other payloads. Skylab achieved a good deal, and the Shuttle was designed to supply Skylab in addition to Apollo. However, when Skylab re-entered the atmosphere in 1979, the Shuttle became a fly-alone. Like the Soyuz, it can accomplish things alone, but also like the Soyuz, its true function is simply as a ferry to a space station.

Having LEO capability does not capture the public's imagination the way that the first Apollos did. Nor does it achieve much - we do not break a great deal of new ground in LEO at the moment (at least from the Shuttle). The Moon and Mars constitute entire worlds to explore, and I think they should be NASA's focus now.

The ISS is a political program designed to give the Shuttle somthing to do -but the cost is ridiculous. Comparing the cost of the ISS to Skylab:

Space inside Skylab = approx. 10,000 cubic feet
Cost of Skylab = $7 billion
Cost per cubic foot on Skylab: $700,000

Space inside completed ISS = 43,000 cubic feet
Cost of ISS = $100 billion
Cost per cubic foot on ISS = $2,325,581

Note that Skylab was launched in one day, by one rocket. Also, the 43,000 cubic feet was for the completed Station which would have included the Habitation Module and other cut components. The Station is truly a waste of money.

Cost of ISS: $100 billion
Skylabs that could be built for $100 billion: about 13

Imagine the size of 13 docked Skylabs! A true superstation. And if the Saturn V still existed, we would almost certainly have a small lunar outpost.


America needs a heavy-lift booster like the Saturn V for several reasons. From another thread:


The Apollo Saturn was not just useful for going to the Moon. Any payload could be stuck on top, such as Skylab, and the launcher would have the brains to put it in just about any orbit you wanted. All by itself. Just imagine the size of space station we could have had up there by now! If they really wanted the Shuttle, fine. Build one. But don't dump the tried and tested method we already had for slinging great lumps of kit into orbit. That was just plain madness. The Russians figured this out years ago. The US has had this fact rammed down it's throat this year, what with Columbia and the Russians picking up the pieces. But noooo, we can't dump the 3 remaining Shuttles and cut our losses. We have to throw even more money and effort at a waste of point vehicle.

Cost of ISS: $100 billion
Skylabs that could be built for $100 billion: about 13

Imagine the size of 13 docked Skylabs! A true superstation. And if the Saturn V still existed, we would almost certainly have a small lunar outpost.

So America needs to focus on three things for the next ten years, even though I don't think they will: buiding a new heavy-lift booster or getting more Saturn Vs; redesigning the Station (Perhaps an orbiter could be converted to this (http://www.space-frontier.org/Projects/ExternalTanks/entrepreneurs/stslab__a_low_cost_shuttle.htm) and then attached to the Station components already on orbit); and designing a safe SSTO capability.

But I am digressing for the point. Manned spaceflight's benefits will always outweigh the risks. Space contains an almost infinte number of new worlds for us to explore, and even our own solar system has many planets and moons. Our exploration of space is just beginning. Yes, there

Here is an essay I wrote about the space program soon after Columbia when there were those who were speaking against it:



Since the beginning of history there have always been two types of nations. There are those who live day to day, taking what they can from their neighbors or their surroundings; and those who seek to expand their world or horizons and leave things better than when they found them. One of the things that has made America a world leader is our willingness to explore, take risks, and find ways to improve the world around us. The question today is not whether we can continue to explore space while we face other problems, the question is: can we afford not to? The space program has already unalterably changed our lives and our understanding of our planet.

What has come out of the manned space program? Here are just a few examples: satellite phones and television, smoke detectors, microwaves, joystick controllers, ski blankets, Velcro, cordless tools, bar codes, ear thermometers, and firefighter suits have all come directly from the manned space program. There have also been the intangible but priceless benefits of advancing scientific knowledge about previously unknown, alien worlds.

In addition, important humanitarian advances have been made by the manned spaceflight program. Fifteen years ago, who would have thought that we would be cooperating with Russia and fourteen other countries to build a manned orbiting outpost hundreds of miles up? Thanks to the space program, we can now predict floods, famine, and other natural disasters in poor countries such as Bangladesh or Mozambique, saving many lives in the process. Due to technology developed from spaceflight, including robotics, it is now possible for doctors to perform surgery on patients halfway across the world who might be too poor or sick to travel to another country for needed surgery. NASA is currently planning experiments to be done on the International Space Station may lead the way to a vaccine for AIDS.

Mankind needs a challenge to prosper. Starting in the late 1400s, we began to explore the great Western Sea. America was discovered, and soon ever better ships were being built to get to America faster and faster. Technology and culture blossomed as we embraced the challenge of settling the New World. When America was born, the new challenge was to expand westward. The railroads were eventually built to facilitate transport, and the telegraph emerged for faster communication. Then, around the turn of the century, we started to electrify our cities. Cars became common, and two bicycle salesman named Wright started playing with a flying contraption. By 1960, Americans enjoyed an ever improving standard of living as technology geared up for the moon race. But when the moon landings ended in the early 1970s, progress slowed down. The only real change from 1975 to now has been the widespread use of computers. Other than that, we have reached a plateau. The world has been colonized and is growing ever more crowded. The only place to expand is outward. Our next challenge is the infinite panoply of worlds in outer space.

We now face a decision. To paraphrase American engineer Robert Zubrin, there are two paths for mankind to follow. One looks easy and straight, and may even slope downward a little bit. This is the path without space travel- we forego a challenge for an easier but infinitely less rewarding route. There is another way, though. It is long and strenuous, and unquestionably leads uphill. But there is no limit to this path. Its top is reached only at the stars. And on that note, I’ll let someone else end for me. There is a wall on the Library of Congress inscribed with the following words by the poet Edward Young: “Too low they build, who build beneath the stars.”

tracer
2003-Jul-24, 01:54 AM
Cost of Skylab = $7 billion
$7 billion in current dollars, or $7 billion in early 1970s dollars?

SpaceTrekkie
2003-Jul-24, 02:55 AM
I read two sig lines on this board that basically sum up my opinion one has already been said in the tread..."Too low they build, who build beneath the stars" and "Earth is the cradle of man, but one can not remain in the cradle for ever"
Manned missions are worth the risk ...at least in this future astronaut's opinion.

kucharek
2003-Jul-24, 07:24 AM
It is a vehicle which is used in the 2000s, although it is a product of 1970s technology and 1960s designs.
Not really an argument. The same is true for a Boeing 747, though newer ones are modified in many places. But that's the advantage of building a continous series and not only a handful. Somehow the problem with the Shuttle is, it is reusable :wink: If they would have to built a new one all the time, design could have evolved much more.

Doodler
2003-Jul-24, 01:58 PM
Actually, given the money they have put into upgrades, aren't the shuttles on their third set of engines? Almost all of them have had their computers and cockpit controls replaced by now with the new 'glass cockpit' arrangement, I'd say the chassis and some of the skin components would be all that's left of the original shuttles, maybe some plumbing and secondary systems like the robot arms, which I am sure some engineer has been tinkering with. Technology doesn't advance in all areas equally, so some systems likely have not improved significantly since the 60s and 70s.

BigJim
2003-Jul-24, 04:23 PM
$7 billion in current dollars, or $7 billion in early 1970s dollars?

I believe it is in 1994 dollars.


Not really an argument. The same is true for a Boeing 747, though newer ones are modified in many places. But that's the advantage of building a continous series and not only a handful. Somehow the problem with the Shuttle is, it is reusable If they would have to built a new one all the time, design could have evolved much more.

But there are a few major differences. The Shuttle is still an inefficient design that lacks a lot of capabilities. Boeing 747s have been constantly upgraded through the years - sure, the Boeing 747-100 may have been introduced during that time period, but the aircraft has advanced through the years, to a much greater degree than the Shuttle. The shuttle was originally designed to fly 40 missions a year, which would have made it economical. But it ended up flying about 4 a year. It simply costs too much for what it is capable of.


Actually, given the money they have put into upgrades, aren't the shuttles on their third set of engines?

I'm not sure if you mean the literal SSMEs, but those are replaced after almost every flight.


I'd say the chassis and some of the skin components would be all that's left of the original shuttles, maybe some plumbing and secondary systems like the robot arms, which I am sure some engineer has been tinkering with

You'd be surprised. There are a few major things that remain in the orbiter. One of those things is the heat tile system. And my point is not that the orbiter systems are dated, which most still are, but that the entire STS design is dated and inefficient. The SRBs and ET are still used on the Shuttle, and those are extremely expensive. You're told that the SRBs are reusable, but only after extremely extensive processing. It's really not that much better than building new ones. The ETs are built new after every flight. A true reusable STS-like ferry system would probably need a liquid flyback booster. But a manned space access vehicle used solely to gain access to space and maybe carry minimal cargo would probably be more like either a rocketplane or an Apollo-type capsule. One of the problems with the Shuttle is that it tries to be a ferry and our only space access vehicle at the same time. It was originally designed to complement, not totally replace, Apollo.

Glom
2003-Jul-24, 04:59 PM
I always wondered how solid rocket motors could be that reusable. Surely it's no easy task fueling up a solid rocket motor.

It is often said that the Space Shuttle failed because it was intended to be an all things to all people spacecraft.

Consider Mir. The big honkin' laboratory was in orbit. Soyuz was used to upload and download personnel. Progress was used to deliver cargo. Proton was used to deliver new modules. The right system for the right job. The Space Shuttle tries to do all those things in one. Of course, having said that, without a space station in orbit :evil: , the Space Shuttle has no where to go so it needs to ship the space station with itself.

tracer
2003-Jul-24, 05:11 PM
I always wondered how solid rocket motors could be that reusable. Surely it's no easy task fueling up a solid rocket motor.
I'm guessing it's like reloading ammunition cartridges: the primer is cheap, the powder is cheap, the bullet is cheap, but the brass casing is expensive. If you reuse the casing, you save most of the cost of the cartridge.

Of course, ammo reloading doesn't require all the safety precautions involved in solid rocket booster reuse. If your brass casing develops a microscopic crack that you don't detect, the worst that'll happen is that your cartridge will misfire when you shoot it. If your solid rocket booster develops a microscopic crack that you don't detect, though, you could end up with a repeat of the Challenger disaster -- so, you spend nearly as much time and money making sure your used solid rocket booster casings are in flawless condition as you would building a new solid rocket booster casing in the first place!

Doodler
2003-Jul-24, 05:22 PM
About the engines, I misspoke. I meant aren't they on a third generation of engine design. The engines I thought weren't replaced every flight, but refurbished, which is why the cracking problems of last year were such a scare, certain components of the engines must be seeing multiple uses. As for the heat tiles, aside from a full bore heat shield like the old capsule, have we really come up with anything better in the intervening years?