Beyond the Shuttle

Tech Central Station ^ | 02/05/2003 | Gregory Benford

[Liberal Classic]

A friend at NASA's Marshall Space flight Center in Huntsville, Alabama told me today that all his engineer friends were working on their resumes. After the Challenger disaster, NASA dithered for 2.5 years before using the shuttle again. How long this time?

Quite probably, a year--if ever. This second wreck calls into question the entire shuttle program. Voices already are calling for a wholly new approach. The shuttle has the worst safety record of any launch vehicle, and is the most expensive, costing half a billion dollars per mission.

And we now contemplate a war in Iraq that depends on our technical prowess. I doubt that Americans will be moved to doubt our military, just because an advanced spacecraft fell out of a clear blue sky. We are tougher than we may look--and more resolute. The country is reasonably united, and yet again the president has responded with the right sense of gravity. He does disaster well.

Still, it is a good time to reassess. Early results from the telemetry and the huge debris field suggest that the thermal tiles failed. One amateur observer saw something blowing off the shuttle as it passed over California, possibly red-hot tiles. We know that a piece of foam blew off the fuel tanks at launch, striking the shuttle's left wing, a location that seems implicated in the heating spike that the telemetry recorded just before the craft began to slew and tumble.

Reentry is a tricky negotiation between gravity and aerodynamics. Controlling descent angle is important to reduce mechanical and thermal stress on the spacecraft, and an error in the on-board computers can allow the angle to get so steep that the craft breaks apart. (Multiple computers should reduce the risk, but that has not saved computer-run aircraft like the SAAB 39 Gripen from the occasional crash.)

Whatever the fault, tiles or computers or human error, the crash occurred at what many engineers thought was the most dangerous portion of a shuttle's flight. This is not a fluke; the system was vulnerable, and it failed yet again.

Perhaps the only good thing about this disaster is that it will prompt NASA to rethink the design of manned spacecraft from first principles. Foremost is that the more complex a spacecraft is, the more things can go wrong.

The safest manned descent module was also the simplest: the Soviet "sharik" descent capsule, which was used by Vostok and Voskhod craft, and also in many unmanned missions since. It was just a sphere with the center of gravity on the side with the thickest ablative thermal shielding, so it was self-stabilizing. Even if the retrorockets failed to separate, it could re-enter safely. Simple ballistic craft that do not fly are also (relatively) simple.

With a spaceplane like the shuttle, however, you are not only committed to a complex shape, you are also committed to using brittle ceramic materials for thermal shielding. The first item on NASA's agenda will be to revisit the tiles issue.

The ceramic tiles not only make overhaul very time-consuming and expensive - specialists affix each tile by hand, managing to do a few per day, and there are thousands - they are also literally impossible to check for inner defects. Unlike metal components, you cannot test them for small cracks that may cause failure.

One way around this is to use many small ceramic tiles, so the spacecraft can survive losing individual tiles. But if several adjacent tiles are lost, it will cause catastrophic failure during reentry. Maybe that happened; it is consistent with what we know now (or are likely to know for several months).

A second line of defense is to have the crew in a detachable unit that can land safely. This would be straightforward in a ballistic craft, but with an aerodynamic spaceplane it is difficult to squeeze such a unit into the nose. On the B-58 bomber the crew had small individual pods that enabled them to eject safely at supersonic speeds, but the weight penalty ruled out this option for the shuttle.

Ideally, you need a descent module that can take a lot of punishment. But a big spaceplane would get impossibly heavy if it was stressed for this. This is another argument for small sixties-era crew capsules.

Ironically, the Soviet "Buran" shuttle could lift loads to orbit without any crew at all, and might make a viable alternative to the U.S. shuttle. But the only remaining craft got badly damaged when a corroded hangar roof fell down on it last year - a symbol of the Russian program's decay.

The safest manned spacecraft built was also among the cheapest and simplest. The lunar lander used pressurized tanks, eliminating the need for turbo pumps, and the fuel and oxidizer self-ignited when mixed, making the engine very reliable.

NASA considered mass-producing similar, simple rockets in the sixties as an option to make space flight cheaper. Political considerations favored the more spectacular spaceplane solution. To date, this decision has killed two shuttle crews and cost billions.

In the end, the next months will try NASA as never before. It has tried to convince its public that going into space is safe, when it is not. Once is an accident, twice is a defect.

The shuttle's justification these days has been its role in supporting a space station that now does little science. The station runs with the minimum crew of three, to save money while forgetting science. The Russian Soyez vehicle could cycle crews and probably will be used to bring down the three up there now.

The station program can limp along for a few years with two flights a year, to cycle crews every half year and not abandon the station entirely. A Russian Proton rocket can continue to boost the station up as its orbit decays from atmospheric friction, as we now do routinely.

This can go on until NASA can decide what to do. Its habit is not to be truly decisive, but now its back is to the wall. It must confront the big question:

What is the American destiny in space? The station is not a destination; it is a tool. But for what?

NASA has played up the station as "a stepping-stone to the planets" - but it cannot perform the two experiments we know must be done before any manned ventures beyond Low Earth Orbit begin.

These are, first, development of a true closed biosphere in low or zero gravity. The station recycles only urine; otherwise, it is camping in space, not truly living there.

Second, we must develop centrifugal gravity. Decades of trials show clearly that zero-g is very bad for us. The Russians who set the endurance records in space have never fully recovered. Going to Mars demands that crews arrive after the half-year journey able to walk, at least. No crew returning from space after half a year ever have, even for weeks afterward. So we must get more data, between one gravity and none. Mars has 0.38 g; how will we perform there? Nobody knows.

Spinning a habitat at the other end of a cable, counter-balanced by a dead mass like a missile upper stage, is the obvious first way to try intermediate gravities. The International Space Station has tried very few innovations, and certainly nothing as fruitful as a centrifugal experiment. Until a livelier spirit animates the official space program, the tough jobs of getting into orbit cheaply, and living there self-sufficiently, will probably have to be done by private interests who can angle a profit from it. But not right away.

This is an historic moment, one of great opportunity. NASA can either rise to the challenge and scrap the shuttle, or just muddle along. An intermediate path would use the shuttles on a reduced schedule, while developing a big booster capable of hauling up the big loads needed to build more onto the station. This would be cost-effective and smart.

The past Director of NASA said to me a few years ago that he thought the agency had about a decade to prove itself. Around 2010 the Baby Boomers will start to retire and the Federal budget will come under greater pressure. Space could go into a slow, agonizing withering. He thought this was a distinct possibility if NASA did no more than fly around in cycles over our heads. "It has to go somewhere else," he said.

The obvious target that has huge scientific possibility is Mars. Did life arise there, and does it persist beneath the bleak surface? No robot remotely within our capability can descend down a thermal vent or drill and find an answer. Only humans are qualified to do the science necessary, on the spot.

A Mars expedition would be the grandest exploit open to the 21st century. It would take about 2.5 years, every day closely monitored by a huge Earthside audience and fraught with peril.

This is what we should be doing. Such an adventure would resonate with a world beset by wars and woes. It has a grandeur appropriate to the advanced nations, who should do it together.

The first step will be getting away from the poor, clunky shuttle, a beast designed 30 years ago and visibly failing now. How we respond to the challenge of this failure will tell the tale for decades to come, and may become a marking metaphor for the entire century.

As well, the engineers at NASA would be overjoyed to have a larger prospect before them, something better than patching up an aging shuttle that, in the end, was going nowhere.

Gregory Benford is a professor of physics and astronomy at the University of California, Irvine, a long-time advisor to NASA, and a novelist.

[Liberal Classic]

I haven't seen this posted yet, and I saw it through Slashdot. This is generally considered a good essay, but there are some problems with his figures as pointed out by Slashdot readers. He claims that the Shuttle is the least reliable launch vehicle we have, which isn't exactly true. The shuttle has a 98% success rate, whereas the Delta rocket which is considered reliable only has a 97% success rate. Soyuz has had two failures already, but has not exceeded 100 missions, like the shuttle has.

Putting that aside, I like this article because it points out what our current space program isn't getting us. We need to develop two things to make our space program useful for human spaceflight: One, rotating habitats, and better recycling. These two things are highlighted in this article, and they're vitally important to human habitation of space. Without artificial gravity, we are doomed to failure.

I personally think a manned mars expidition is little more than a publicity stunt, as has been said about the moon landings. The difference with the moon is that it is quite close by, as astronomical objects go, and makes a good launch platform for points unknown. It also has been proven to have water, and other necessary metals and the like. Personally, I would support renewed moon shots rather than a manned mars mission. The one drawback that the moon has is its reduced gravity, which means it has the same drawback as any space habitat without artificial gravity. I don't think the moon will be a for permanent settlement, but I do believe it is a useful base of operations.

As an aside, I do not think Mars is very useful in terms of the long term survival of mankind. Life grows exponentially, and even if Mars is terraformed to a best case scenario, the maximum carrying capacity of our solar system has only been increased 100%. Plus, Mars has all the disadvantages Earth has, such as a large gravity well. To grossly oversimplify, I am in favor of building hundreds and thousands of Babylon 5 style space stations.

For further reading, see the excellent Space Settlement FAQ by Mike Combs.

[lepton]

One of the issues, is that we must have enough stuff up there to hold enough workers (human or robotic) to prepare for the later steps. As the Space Station gets bigger, it will be able to hold more people, which will enable it to do more things.

The Space Shuttle is old, and technologically marginal. Compare the Columbia to the Endeavor...then look at what a new generation craft might be able to do. The crafts that he describes as apparent alternates are wholly unable to do more than a few of the Shuttle's missions, aside from the essential return to earth.

[Arkie2]

I know it is politically impossible to abandon manned spaceflight but the most productive use of our resources would be many robot probes instead of the dead weight of the ISS. There are several new technologies that need to be explored. The ion engine has proven itself in space and coupled to a nuclear power source could explore the outer solar system. There are even several innovative ideas waiting in the wings such as solar sails and the space elevator which would cut the cost of taking loads from the earth to orbit. I would love to see NASA return to an engineering agency instead of what it has become which is a means to conduct politcs in space. That's why we have the bloated and useless ISS, so Russia and some European countries can "participate" in joint ventures in space with us. Scrap manned flight for now and get on with exploration.

[Liberal Classic]

Part of what I got out of his essay is the Keep It Simple, Stupid principle. Perhaps a simpler manned launch vehicle and a larger heavy-lift vehicle are what we need. Not that the shuttle isn't a bad idea, but I've heard that having both the space station and the shuttle is like having a recreational vehicle and a cabin out in the woods. Are both really necessary, when one would do the job? Maybe we need a simple car to get into orbit to visit the cabin. Or perhaps we just need the Winnebago?

Certianly a resuable vehicle has (in theory anyhow) a cost advantage. Perhaps the next shuttle should be a lighter manned vehicle with less cargo capacity, and a giant simple lifting body for cargo. Separate the manned part from the cargo part.

Pardon my disorganized post. I'm just woolgathering while working on the weekend.

[supercat]

A reusable spacecraft might be cheaper than one-time use vehicles if the extra weight required for reusability didn't make it so big and heavy. Frankly, I'd rather see an assembly line set up to produce a thousand one-time use vehicles; I'm sure that economies of scale would kick in in a big way with that large a project; further, research into test procedures would be amortized over the whole lot, allowing more thorough testing to be done cheaper than is currently possible.

[supercat]

The International Space Station has tried very few innovations, and certainly nothing as fruitful as a centrifugal experiment.

How hard a concept is an oversized centrifuge? Why hasn't such a thing been built? For that matter, what are we really doing with the ISS anyway? Building space for three people, with never any ambition for more than seven? How's that thing any better than Mir (which the Russians got up a lot cheaper)?

[Liberal Classic]

I'm no economist, but it sounds like to me that the economy of scale from a mass production assembly line would in the long run be less expensive than a small number of highly expensive, but reusable vehicles?

[RightWhale]

the most productive use of our resources would be many robot probes instead of the dead weight of the ISS.

The only question about the Sagan approach is that if we don't intend to send men into space and to build settlements and colonies and in fact don't intend to develop the resources of outer space, why bother with robots?

Pure science? Knowledge? A noble endeavor, but hardly worth a dime of public money.

[Mamzelle]

re: I would love to see NASA return to an engineering agency instead of what it has become which is a means to conduct politcs in space. )))

And to provide rides, vicarious and otherwise, to the aviation-addled.

[Batrachian]

They cancelled the X-33 (Venturestar) program because of delays, cost overruns, and engineering problems, but it had a lot of promise. No tiles, at least. Now they have nothing to fall back on and have to start from scratch again. The worst-case scenario is to try and keep the shuttle program going. It's a capable craft, but is too expensive, too limited in terms of availability, and too dangerous.

In the 1960's, they started working on a replacement for the Saturn rockets (before the shuttle came along and killed it). It would have been able to boost 1 million pounds gross weight into orbit. With today's technology it would be easy, and would be far more capable, safer (unmanned), and cheaper than the shuttle. It would be capable of lunar and other deep space missions, which the shuttle cannot do. It should be resurrected, as should the Venturestar program.

Let's use this disaster as a new starting point for a revitalized space program whose goals would be space colonization, pure science, and commercial exploitation of space.

[bribriagain]

The advances in shuttle technology and the advances in understanding human physiology are reaching a crucial intersection. Longevity and modifying the human body to be more "space friendly" could change the way we look at future space flight IMHO.

Set the long term goals first: "The stars our destination". Then figure out the platforms and steps needed to realize that goal.

[Redleg Duke]

Growing up in the 50s and seeing Dr. Von Braun on Disney, describing the ring space station, I don't understand why that hasn't been seriously considered. I suppose the NIH factor may have something to do with it.

All I know is that NASA has gone from a "Can-Do" Space Agency to a "Can't-Do" Bureaucracy and all we have left are memories of the greatest engineering and scientific team in history that was sacrificed on the alter of the "Great Society". And to what end?

[ZOOKER]

The ISS was designed for zero-gee operations, not to be spun around at the end of a cable. IMO, trying such a stunt would break it into pieces.

Furthermore, its interior ergonomics are zero-gee too. Under gravity, half of its workstations would be on the ceiling.

Simulated gravity is a good idea, but we would need to start with a blank sheet, not try to adapt the ISS to it.

As for unmanned expendable boosters, there are already many to choose from. Assembly lines are already running for satellite customers, all it would take is a phone call to increase capacity for ISS support.

[ffusco]

I would be in favor of NASA building the USS Enterprise from Star Trek. But seriously, Bio-Sphere failed as a self-contained space ship on the ground so I doubt we could permanantly settle or live in space for anther 100 years. Our space program is seriously flawed: no new launch vehicle, 7 y.o. space station practically useless, another "feel good international stunt" w/ no return on investment, no new rockets....

[Stefan Stackhouse]

What is the American destiny in space? The station is not a destination; it is a tool. But for what?

Travel to Mars, or "scientific exploration" are exactly the wrong objectives. They can become valuable adjuncts, but if one reviews the history of terrestrial exploration and settlement, you will find that it has ALWAYS been MAINLY about acquiring cheap and abundant resources -- mainly gold and land, with a few other assorted things like spices thrown in for good measure.

Petroleum is eventually going to become more scarce, but the people who think that just putting a solar collector on every roof and a wind generator in every back yard is the solution are hopelessly idealistic and naive. Solar energy might be part of the solution, but only if it can be harvested from massive facilities taking up a lot of room, in places where the sun shines 24/7/365, with no clouds or even atmospheric scattering to get in the way. Guess where that place is? The other big answer will be fusion. Again, we are NOT going to have little "Mr. Fusion" engines in our car like the guy had in "Back to the Future." If this technology is ever developed to the point of being economical, it is going to require huge facilities. The extremely high temps and pressures, and the extremely high levels of neutron release, are going to make these dangerous facilities to be around. Plus, it might just be easier to engineer them in a zero-g environment, so once again, space might be a good location. How to get the energy transported to earth. We'll probably need orbiting facilities that will take the energy produced by the solar arrays plus the energy produced by the orbiting fusion reactors to produce deuterium and tritium. Chill it down close to absolute zero, put it in a big stainless steel vacuum thermos, pop it in a re-entry vehicle, and send it to earth, where it becomes the feedstock for the terrestrial fusion plants. He3 (which can become the feedstock for the tritium production) is present in huge quantities on the moon, so we'll have to set up a major mining operation there.

Our terrestrial mineral supplies will eventually be getting scarce, too. There's a gazillion asteroids orbiting the sun, all made of all types of interesting minerals. It should be possible with a little bit of effort to send robotic spacecraft out that can attach themselves to an asteroid, and then through a series of carefully directed and timed thrusts gradually move an asteroid into the same orbit as the earth, but either leading or trailing us by a safe distance. We can then send crews out to mine these asteroids, and transport the ores to orbiting mills for refining. Much of the earth's heavy industry could eventually be relocated to earth orbit, which would provide two big advantages: 1) less pollution here on earth; and 2) development of a self-sustaining infrastructure in space (which will be absolutely essential before we can even begin to consider any exploration farther away).

The biggest advantage of pursuing a resource development/industrial infrastructure track is that this provides a logical and feasible pathway for private sector involvement and financing. Rather than just buring up dollars every time we launch stuff into space, we can actually turn space into a profit sector. That is the ONLY way that the long-term future of space exploration can ever be secured.

This is what our big-picture vision needs to be for at least the next 50-100 years. Once the infrastructure is in place and space development is a "going concern", THEN we will be ready to consider more adventurous steps to the planets and even nearby stars.

[Liberal Classic]

Simulated gravity is a good idea, but we would need to start with a blank sheet, not try to adapt the ISS to it.

No argument there. I'm not suggesting spinning ISS around on a line. Rather I think the Spacelab/Mir/ISS concept is already outdated. Perhaps there are some longer term studies that can be done on ISS that can't be done on the shuttle, because the shuttle doesn't have the duration needed. Most of these studies involve the effects of weighlessness on living organisms, which in my opinion is the wrong thing to now be studying. We know that zero gee in the long term is terribly detrimental to human life, and while the effects of zero gee on plants and lower creatures are interesting, of what worth are they when we already know how harmful zero gee is? Perhaps some good will come from plant weightlessness studies, but I think now is the time to start approaching the problem from the other direction: how do we start making artificial gravity to avoid the harmfull effects of weightlessness.

This is not a question that the shuttle or ISS can easily answer. IMO, I think we need to start thinking about those rotating ring stations, heavy lift capacity, and smaller safer manned vehicles.

[Liberal Classic]

Good post. Science has become the end not the means of space travel today.

[Liberal Classic]

Longevity and modifying the human body to be more "space friendly" could change the way we look at future space flight IMHO.

Why worry about tinkering with human physiology, when all we need to spin ourselves around in a circle to make the illusion of gravity to prevent all those detrimental side effects. The use of genetic engineering to facilitate space travel for now is in the realm of science fiction. Part of the problem is that once a body is adapted to life in zero gee, they can't visit earth ever again. I think we need to build habitats we can survive in rather than building a better man to live in space.

[supercat]

One thing I was wondering about: if a space station isn't rotating to produce artificial gravity (many experiments require zero-G, and it may be most practical to not have the whole station rotating) would it be practical to set up a running track around the inside of a cylinder and run on that? Would the cylinder have to be rotating, or could one get accustomed to "running" using nothing but ones own momentum to press one's feed against the "ground"?

I guess spinning the cylinder a bit might not hurt, and would increase the "apparent gravitation" to better approximate 1g. Still, my impression is that zero-G is not in and of itself harmful provided that crews get sufficient exercise in a simulated gravitational environment.

[Liberal Classic]

Good questions to which I do not fully know the answers. From what I've read, the absence of gravity seems to lead to loss of calcuim in the bones, the process of which execise is only party successful at delaying. There's no way to excercise you skull bones, or inner ear, for example, unlike the extremities. It seems to be the force of resistance pulling against the bone that stimulates the calcuim deposits. In zero gee, there's nothing pulling on your bones at all, and so your cells don't bother with replenishing those calcuim deposits.

Now, all the footage of excercise in zero gee that I have see is of a guy strapped into an excercise cycle, peddling away. I think it's easy to understand how this wouldn't be a full body workout. However, what you suggest, running in a big treadmill much larger than that of spacelab, might be some help, because even though you're pushing with your legs your whole body is being jostled around. Something like this, incidentally shown in 2001: A Space Odyssey, might help slow down this effect. The problem is you can't have your spacemen in the gym 24 hours a day, or they won't get any real work done.