X-33 Shuttle Problems

SEWilco writes: "This AP story points out major problems with the X-33 prototype shuttle. It's out of money and the composite hydrogen tank came apart in a test. The aerospike engine test seems to be doing nicely, but it needs a ship attached. Congress is considering NASA's Space Launch Initiative Program, which apparently includes more X-33 funding along with considering other technologies. The Delta Clipper is my favorite, although the ET Scenario engine-only-return design is interesting."

Comments

Re:Urgh.

[Moofie]

Let's back up a little bit.

Fuel is cheap. Maintenance is expensive. There is a certain amount of energy you have to dump into one pound of stuff in order to get that stuff into space. The least expensive vehicle is the one that weighs the least.

What makes a single stage craft horribly wrong is that it WILL weigh more than a staged rocket. End of story.

There's nothing magic about SSTO that makes it cheaper than the Shuttle (whose alleged cost savings have NEVER been realized). The economies are supposed to come from simplified servicing and maintenance. Therefore, IF you can service the thing for less than the cost of a similar capacity rocket, it's economical. This has not proven to be the case.

And before you start hollering about people who don't know what they're talking about, let's discuss this "fuel per square pound" idea you've got in your post. I'm REALLY sure that this measurement has nothing whatsoever to do with rocketry.

Re:Urgh.

[Zarniwoop]

I knew I would get a reply like this. You seem to have missed my point, entirely.

I'm saying the technology for an efficent SSTO rocket isn't here yet. First off, you need to have an extremely light rocket, or its not even going to matter. Consider this:

To lift the mass of a single stage launcher using hydorgen/oxygen rockets (currently our highest conventional specific impulse fuel), you have to carry along eight times the unfueled weight of the rocket in fuel.

You must now have an extremely light, large rocket. So, it pretty much has to be built out of composites. You now have a really big fuel tank with a payload. So let's consider the engines.

You need some damn powerful engines, and damn adaptable engines. Bell rockets won't cut it- the Aerospike is the only concept that even comes close. So, you have a rocket made out of emerging materials on top of a semi-proven rocket design (I say semi-proven since the Aerospike has never been used, to my knowledge, on an actual rocket). Quite a bit of stuff to develop. Quite a bit of unproven technology.

And now, since you have 8 to 1 propellant to spacecraft, you don't have a real lot of room left over for the payload.

What I'm saying is that SSTO is quite the challenge. It's something that I'm not sure that is feasable, as yet- theres a lot of unknowns. To this date, the best alternative is staging- you drop weight as you go. Since you drop significant weight with each stage, you have less rocket to keep going. The (as promised) VentureStar might be uber efficent, but I suspect that when it hits the cold, hard light of reality, that tenfold reduction of cost argument will fall through, just as it did with the Space Shuttle. If they even get it into orbit- there is yet to be a rocket built capable of a single stage insertion into orbit.


What do I do, when it seems I relate to Judas more than You?

The NASP(X-30) and X-33 are two different things

[jhesse]

X-33 info: http://x33.msfc.nasa.gov/index.html
X-30 info: er, I can't find any in three minutes of searching. However there are some pretty pictures.


--
"I have also mastered pomposity, even if I do say so myself." -Kryten

Re:Urgh.

[brucehoult]

The big problem of a vertical launch is that 80% of what you lift is fuel, and is spent on the way up. Why not put an SSTO craft like the Venture Star as a second stage on the back of a big and fast aircraft, a modified 747, 777 or Beluga for example? Simply fly that aircraft as high and as fast as it goes, maybe stick a rocket on it to gain some extra height and velocity at its ceiling to launch the second stage.

It's a good idea, but it has problems. You're severely restricted in the size you can make the spacecraft by all sorts of things. You've got to be able to support the fully-fuelled spacecraft on top of an aircraft not originally designed for that, which means extensive modifications. Look at how much trouble NASA had to go to with the Shuttle transporter aircraft, and the Shuttle rides empty. As well as structure, that impacts takeoff speeds and runway lengths. Note also that tthe maximum takeoff weight of aircraft such as the 747 is far more than the maximum landing weight -- if they have to abort early in the flight then they normally have to dump lots of fuel. That's tricky if the weight is in a spacecraft.

There are also operational problems. It takes time and special equipment to mount the spacecraft on top of the carrier aircraft, which means expense. You've also got to be careful not to land the spacecraft anywhere that the carrier can't fly out of.

If you possibly can fly SSTO -- even with a very small payload -- then you're probably better off to do that than to use a piggyback carrier aircraft. See however Len Cormier's Space Van concept, which looks quite interesting.

Other alternatives for a 0th stage include KellySpace's concept for using a 747 to tow a spacecraft (already tested by towing a jet fighter), and Pioneer Rocketplane's concept of the spacecraft and a tanker taking off seperately (possibly from different locations) and doing aerial refuelling.

Both these concepts have advantages over a piggyback arrangement, through reducing the loading on the 0th stage aircraft's structure. I think the Pioneer proposal is the best. It allows a lightly-loaded spacecraft to take off from almost any commercial runway where the payload is, while the tanker takes off from a longer strip possibly hundreds of miles away. The undercarriage of the spacecraft doesn't have to carry the fully fuelled weight (giving a weight saving) and the wings only have to be big enough to carry the fully-fuelled vehicle when travelling at 500+ mph, not when at a 100 - 150 mph takeoff speed, for a huge weight saving.

Pioneer have done detailed design of their intitial aircraft, right down to the point of getting fixed price quotes from the likes of Boeing to actually build it. What they haven't been able to organise is the funding. I don't think anyone seriously doubts that their idea will work, the question is whether an investor will make money in the current environment, especially with Iridium having gone bust and Teledesic cutting back their plans drastically.

... and America is just a heap of dirt in the sea

[hwilker]

At least that would be the equivalent reaction of a 15th century explorer to the discovery of that annoying chunk of land mass sitting right on the sea lane to India.

I often try to decide whether space exploration is comparable to the sea voyages undertaken by 15th to 18th century mariners. These voyages were comparable in risk to today's space flights, even flights to the moon and to Mars. Back then, I guess, the motivation for these explorative voyages was partly commercial, partly just human curiosity. Admittedly, they did know that there were spices to be found in India. We (pretty much) know there's water on Mars - let's go there and see what we can do with it!

But no, we don't need to invent new technology. It's all been done before, so why bother? The Commissioner of the U.S. Patent Office declared in 1899, "Everything that can be invented has been invented." For this reason, he wanted his office closed. "No, no - you can't go farther than you can look, it's no use leaving here."

Re:SSTO will never happen. Get used to it.

[HeghmoH]

Interesting, you keep talking about these magical advanced propulsion techniques that will make these trips practical. I have one question:

How do you think those magical propulsion techniques will be invented?

I'll give you a hint. We're not going to sit around on Earth for the next hundred years until somebody says "Hey guys, I just realized, with that space engine sitting in your back yard, we can get to Mars in two hours, so let's go!" The first trip there will be horribly, painfully slow, and then people will come up with better techniques.

Mars is in reach of current technology NOW if anybody wanted to do it, and had the money. Of course, why go to Mars? There are better things out there: asteroids. The metals in the average mile-long asteroid would supply our industries for something like fifty years at the current rate.

People who sit back and wait for things to happen only get away with it because other people are not content to sit and wait.

Forget NASA

[Baldrson]

NASA exists to make the pioneering culture that founded the US have the impression that everything that can be done to open a new frontier for them to escape to _is_ being done. However, what people forget is that central authorities don't _want_ the pioneering culture that founded the US to escape them. It is far more likely that John Carmack will open up the space frontier than it is that NASA will do so.

$1,000 per pound

[Money__]

Part of the X33 design is to respond to the many threats NASA faced from private industry, over the past 8 years or so, that promised to reduce the cost to orbit by a factor of 10 ($10,000 to $1,000 per pound). They've done some truly revolutionary work on the linier aero-spike engine that not only efficiently provides lift from the pad jump to orbit, but also scales up very well (by adding more engines along the back side of the launch vehicle).

The real issue is that many of the private sector solutions to low cost to orbit have either chosen the wrong launch weight, run out of venture capitol, or just not proven to be as affordable and reliable as a NASA launch.

The other thing that needs to be considered about the X33 is that if you can afford to keep it feuled and on the pad, it can be looking down on anywhere on the planet in less than one hour! That's revolutionary.

From the article:
"In the wake of last year's back-to-back Mars mission failures and repeated delays in constructing the space station, a high-profile success would help rehabilitate NASA's tarnished reputation. The X-33 could have produced that success, but for almost a year the space agency has kept the project out of the limelight."

*Nowhere* in the article did they mention the complete *success* of NASA in deploying the ISS. This is hardly a fair reading of the facts.

NASA is attempting to solve hard problems that take time and money to solve and NASA should be given the funding and time to succeed. When completed, this will put our countries space capabilities leaps and bounds ahead of everyone else, and will make projects like LEO comunication constellations finacially feasable.

Re:$1,000 per pound

[brucehoult]

I'm sorry, but there are *so* *many* things wrong in this that I hardly know where to start.

Part of the X33 design is to respond to the many threats NASA faced from private industry, over the past 8 years or so, that promised to reduce the cost to orbit by a factor of 10

NASA doesn't face threats from industry. NASA's job is to explore space, not to build launchers. As long as no one else builds launchers commercially then NASA has no choice but to build their own, but they are required by US law to use commercial services where available.

The threats go in the opposite direction. As long as NASA can get near unlimited funds to build things that they will then provide (near enough) for free to those they judge to be worthy, no businessman in his right mind would invest in a private launcher. You can't compete with the government, even when they're worse.

They've done some truly revolutionary work on the linier aero-spike engine

Aerospike engines are probably great, but no one actually knows for sure because none have ever been flown. There was a project called LASRE which was supposed to fly a small linear aerospike attached to an SR-71. This project got rolled into X-33 and killed. The X-33 engine looks quite good, but they've crippled its chances of ever flying by putting it into a vehicle with huge problems. They should have build something conventional and cheap and low-risk to test the aerospike engine in first, just as they should have build a dedicated vehicle to test the new thermal protection system, and a dedicated vehicle to test the aerodynamics and the multi-lobed tanks.

By rolling everything into a single high-risk vehicle they not only probably spent more money than they would have building specialised vehicles (because of the inter-dependencies and constant redesigns needed -- the DC-X cost $60m, the X-33 has eaten $1b already), but they have ensured that if any single part of the vehicle has problems then the other parts can't be tested at all.

The real issue is that many of the private sector solutions to low cost to orbit have either chosen the wrong launch weight, run out of venture capitol, or just not proven to be as affordable and reliable as a NASA launch.

In what way has this been proven? X-33 doesn't fly at all, let alone affordably and reliably. Shuttle flys barely half a dozen times a year, at a cost of billions of dollars each year. All of the public money was put into one basket. The eggs are broken. For the same money, *all* of the private sector companies could have been funded. Surely one of them would have worked. In fact, probably all of them would have, because they are in general very low risk plans using off the shelf technology.

Wrong launch weight? There are very few large heavy payloads that need to go up in one go. Most of those are military. The shuttles fly twice a year each. A small, cheap, vehicle that could fly every day -- or even twice a week -- would lift in aggregate far more in a year than the shuttle fleet can, and far more flexibly. What is needed right now is a DC-3, not a 747. There is not yet anywhere for the 747 to go, and it will sit half a year waiting for enough cargo to make it worthwhile taking off. That's not good economics.

The other thing that needs to be considered about the X33 is that if you can afford to keep it feuled and on the pad, it can be looking down on anywhere on the planet in less than one hour! That's revolutionary.

Actually, X33, if it ever flies, won't go anywhere near orbit. It was designed to get all the way from Nevada to Montana, but now looks as if it might only make it to Utah. VentureStar is the hypothetical orbital follow-on to X33, but NASA hmade it clear from the start that LockMart would be expected to finance VentureStar themselves. At this moment LockMart don't appear to even want to put up the money to finish X-33 -- why should they when it has been incredibly sucessful at its primary mission: preventing other companies from developing cheap, reusable, launch vehicles so that LockMart can continue to sell the government expensive throw-away rockets?

Even this "can afford to keep it fuelled and on the pad" shows the wrong attitude. Air New Zealand's B747's spend an average of more than 18 hours a day in the air, year round, not on the ground. (I'm sure it's the same for QANTAS or any other long-distance carrier) An aircraft on the ground is costing you money. An aircraft in the air is making you money. That's the difference between NASA and a for-profit company. NASA looks at the cost side of the equation. A private company looks at the difference between costs and revenues.

*Nowhere* in the article did they mention the complete *success* of NASA in deploying the ISS.

You're going to have to define "success" for me. Looks half a decade late and way over budget to me. No one has died, so far. But no one is living there, either, unlike the working space station the other guys deployed fifteen years ago which has had several hundred different people living in it to date.

NASA is attempting to solve hard problems that take time and money to solve and NASA should be given the funding and time to succeed.

NASA has had hundreds of billions of dollars since the last moon rocket flew. There is precious little to show for it. Every indication is that NASA would rather work on solving hard problems and never fly than do things the easiest way they can find and actually put people into space.

Over budget, Under thought

[bonzoesc]

It would be nice if the government could get their aerospace act together and just make something that works, wouldn't it? The X-33 is just another project that has peen hyped and funded too much, and is too manager controlled, and tries to be the swiss-army-chainsaw of rockets. Just make a specialized rocket that does one thing well. It's like comparing the Quake engine to the Unreal engine: one is really fast indoors and in small outdoor situations, the other takes 5 minutes to load a board.

Tell me what makes you so afraid
Of all those people you say you hate

Should be 'politics', not 'science'

[Thagg]

Everything about the X-33 project was decided by politics and not science. People all through the project, from the top to the bottom, knew that the projections were insanely optimistic at the most charitable, bald-face lies would be a better description.

SSTO systems are, in some ways, extremely simple to evaluate. To get a payload to orbit without staging, you have to have both an extraordinarily efficient engine and a remarkably high mass ratio (fuel:everything-else ratio). It was obvious that the X33 prototype wasn't going to get to orbit very early; the mass ratio just wasn't there; even with rediculously risky materials and structures were specified. So, there were two obvious things to do at that point:

1) Kill the project

2) Lower expectations to a technology demonstrator, and cut way back on the risk.

They, of course, chose the insane third option, maintain the (extremely expensive) exotic materials, but still give up on the the idea of going to orbit. So, they ended up with failed tanks, and nothing to demonstrate whatsoever.

The aerospike engines really are a great idea, it would have been extremely useful to see them fly. As it is, there is absolutely no question that the project will be killed. Lockheed even wants it dead. And why not? They got all the money that they could ever get from the program, and they didn't actually have to produce anything at all.

It's very likely that almost every part of the alleged rocket wouldn't have worked; the tanks were just the first thing to fail spectacularly. The engines had very serious problems too (the ramps that are the key to the aerospike concept were much harder to fabricate and cool than 'expected').

On the other hand, the Delta Clipper, funded by McD primarily; was a system that could be tested in stages, and in that testing they took some actual risks; but measured ones. The first test when they flew the rocket and landed it vertically was a big step -- but they managed the risk to the point where they made it happen. The engines, tanks, and almost everything else in those first tests were off-the-shelf items (the aeroshell was a unique thing, but contracted out to Scaled Composites, a company with a sterling record for this kind of thing.)

So what happens to the Delta Clipper approach. It's killed, of course.

In the end, I have no question that the next-generation launcher will be built by private industry either in the US or more likely overseas. Sad, but that's the way it is.

thad

Re:Thanks for the rant

[brucehoult]

The X-33 was a risk, but not nearly such a stunt as the Delta Clipper, which had a marked tenedncy to explode.

The Delta Clipper was an orbital vehicle that was never built. Perhaps you're thinking of the DC-X? That was a subscale demonstrator of vertical landing and low-Mach terminal maneouvering. It was a near-perfect example of what a focussed research and development project *should* be. It tested one thing and one thing only, on a very small budget and short time-scale. And it worked perfectly. The only real thing wrong with it was that research projects should really build two or three, not one. It's only a little more expensive to build several copies than to build one, and it protects against losing the whole project if you crash the vehicle. If a research project is really a *research* project then it must be investigating something that you're not 100% sure you know how to do, which means that if you don't crash a vehicle then you probably weren't pushing hard enough.

The vehicle which burned was the DC-XA. The DC-X safely completed its test program with the Air Force/BMDO, and NASA took it over for a test program of their own devising. They put in a composite tank similar to (but simpler than) the one which is giving so much trouble on X-33 and then a technician forgot to reconnect a hydraulic hose to the landing gear before a flight, resulting in one leg failing to deploy and the vehicle tipping over, cracking the NASA tank and destroying the vehicle in a fire.

Think about vertical landing for a minute. Parachutes and gliders can be made stable much easier than the DC.

But DC-X showed how to do it. That's the whole reason for it to exist.

Vertical landers are also the least efficient of rockets. If it took a Saturn 5 to get to escape velocity, it will take a Saturn 5 to stop a vertical lander at escape velocity.

This is not correct. All reentering rockets rely on friction with the atmosphere to get rid of 99% of their speed. Parachutes, wings, or rockets are used only for the last 1%. If you're bringing the engines back in the vehicle anyway then a little fuel for landing might weigh less than wings (and the extra fuel to lift them into space), or it might not. You need really detailed design work to find out, not just some halfbaked suposition.