Design of Next-Gen NASA Rocket Showing Flaws

caffiend666 writes "According to an AP news article, NASA engineers are concerned about the design for the new rocket meant to replace the shuttle. Work on the project has revealed that the first few minutes of flight could see 'violent shaking', a serious flaw that might destroy the craft soon after launch. 'NASA officials hope to have a plan for fixing the design as early as March, and they do not expect it to delay the goal of returning astronauts to the moon by 2020. The shaking problem, which is common to solid rocket boosters, involves pulses of added acceleration caused by gas vortices in the rocket similar to the wake that develops behind a fast-moving boat.'

Comments

Better to find it now rather than later...

[the_humeister]

...before it's built. Seems like a non-story.

Re:Better to find it now rather than later...

[khallow]

I see two things that make this a story. First, the design process for the Ares 1 would be of interest to slashdot readers. Second, this is pretty far along to be dealing with an obvious flaw of the rocket's design qnd strikes me as another example of the rushed nature of this particular platform. Before this, they had to strip the Crew Exploration Vehicle (CEV) down to basics to figure out how to pare it down to the point where the Ares 1 could carry the CEV. That particular effort was because the Ares 1 in turn failed to meet expectations because they decided not to use the Space Shuttle Main Engines due to the expense. Now, this problem can be fixed, but I'll be surprised if they can do so in a way that doesn't add weight to the vehicle and reduces its performance further. But I guess none of this really is so impossible that money can't fix it.

Re:Better to find it now rather than later...

[khallow]

I disagree. This problem would have been obvious from the start. I simply don't understand how they got so far without addressing it. Sure, they wouldn't have known the full dynamical details of the SRB vibration, but they would know the crude resonance modes of the rocket and that the SRB kicked out vibration in these frequencies. Hence, they would have known at the very start that this was a problem. So why wait at least two years (until right after the Ares 1 supposedly passed its "system requirements review") before you start thinking about this problem? My take is that they put off discussion of it as long as they could. As I see it, the next year is critical not just to Ares 1 development, but to the entire VSE plan. If they haven't resolved the basic design problems with both the Ares 1 and the CEV (and yes, I think there are serious issues to be resolved here), then we might not see any of this survive the next administration.

so what?

[The_Rook]

so they found a problem with a preliminary design. big deal. that's why they call it research and development.

how long did it take to design the saturn Ib/saturn V and make sure that they'd mate well with the apollo capsule? how long did it take to come up with skylab, an orbiting lab that could be mounted on a saturn V?

i expect it'll take about five to six years to bring the orion program to a complete first generation system.

Re:so what?

[Pedrito]

Mod parent up. This is a completely ridiculous article. It's little more than a footnote on a status update of the development.

Re:so what?

[cyclone96]

Indeed. In fact, the Saturn V itself had problems with pogo oscillation, a condition that affects liquid fueled rockets and caused the center engine shutdown during the first stage of Apollo 13.

Re:so what?

[Antique Geekmeister]

Mercury started launched amazingly shortly after Sputnik, in 1957 or so. Gemini launched in 1963, Saturn launched in 1967. That gives less than 10 years to build 3 generations of spacecraft and launch the third generation, successfully.

NASA has known that the Space Shuttle flies like a duck-taped cow since well before its first launch in 1981, since it was designed by committees lobbying wildly to have different components manufactured in different states to get Congressional approval and for many other political, rather than engineering, reasons. Development of replacement spacecraft has been hindered by funding, similar lobbying stupidity, and the unwillingness to admit that rockets have to be built and tested rather than modeled to death for decades before actually trying anything.

Private industry has already shown a far more capable design, when the Ariadne won the X-Prize. But NASA is blocking its development for numerous political reasons, not engineering reasons. You cannot expect NASA to do anything in real development and admit that complex craft are going to crash in the design and testing phase, and treats it as an acceptable risk rather than a political nightmare. And their current leadership is too politically hidebound to do anything profoundly innovative: it would interfere with the "5 year plans" of their contracts with Boeing and other manufacturers.

Re:so what?

[Anonymous Coward]

Mod parent up. This is a completely ridiculous article. It's little more than a footnote on a status update of the development. Not really. This is the first manned rocket that is going to use only a solid rocket booster during its first stage. Why? Because NASA wanted to keep the pork going to ATK Thiokol. The Atlas V and Delta IV Heavy designs didn't have this issue. They were already built and had the capacity needed. The only thing left for either of those rockets would be the man-rating process. Their fault is that they didn't send pork to Utah. Instead we are left with this brain-dead idea where we put people on a rocket with no control over how the first stage operates and no ability to shut it off if there is a problem. Now add in the fact that there is no plausible upgrade path (unlike the Atlas V and Delta IV Heavy). This rocket is going to save no money and it will probably get some people killed before it is finally retired. Solid rocket boosters make sense on payload missions--not manned missions.

Holy cow!

[ruiner13]

You mean they didn't get the design of a prototype exactly right on the first try? Amateurs! Seriously though, where is the news here?

Nasa: Delay if Necessary

[quanticle]

If anyone else has read Diane Vaughan's Challenger Launch Decision, he or she will know that launch schedule pressure from upper management was a leading cause of the rationalization of risk that NASA undertook to justify flying with known Shuttle desgign flaws. Hopefully, in this case, the NASA senior managers are not applying the same mindless schedule pressures that leads to quick fixes and mindless workarounds at the expense of long term safety.

Solid Rocket Boosters

[Bruce Perens]

Solid Rocket Boosters are sort of like strapping yourself to a firecracker. We can't have liquid ones?

Re:Solid Rocket Boosters

[cbcanb]

Because liquid ones aren't made by a certain company in a certain state. It's all politics.

Had any sense prevailed, we'd be sticking a capsule on top of an existing booster -- Atlas 5 or Delta 4 -- and being done with it.

Re:Solid Rocket Boosters

[segedunum]

Solid Rocket Boosters are sort of like strapping yourself to a firecracker. We can't have liquid ones?

You could have liquid ones, but they take an awful lot of development to get right. NASA, and US institutions in general, typically don't like them because of the danger involved (the Soviets have had some major disasters with liquid fuels). The only people who really did get liquid fuels to be fairly safe and reliable were the British and their Blue Streak (HTP was used after the failure of LOX - impractical in an ICBM), Black Arrow and Black Knight projects:

http://en.wikipedia.org/wiki/Blue_streak
http://en.wikipedia.org/wiki/Black_Arrow

These rockets were a departure from everything else around, and used Hydrogen Peroxide as an oxidiser - cheap, readily available and works well at normal temperatures and pressure. Most considered the fuel to be too hazardous, and a Hydrogen Peroxide fuelled torpedo allegedly sank the Kursk (probably not sensible on a submarine), but the British developed ways to handle it safely and efficiently. To this day, no one else has tried this method and its pretty advanced rocketry even forty years on. It certainly gets rid of the dangerous handling of liquid oxygen, which has to be kept ultra cool and under controlled cryogenic conditions.

After a textbook final launch, the project was cancelled. Given the need for commercial satellite launches over the past few decades, the mind boggles as to how cheap and useful this could have been if developed further. The British, as per usual, decided that simply reusing the Scout solid fuelled rocket would be cheaper. Go figure.

Re:Solid Rocket Boosters

[rijrunner]

LOX is routinely handled by thousands of industrial facilities in the US alone. Its properties are well known and it has been used safely for over a century.

    Liquid boosters have been used safely on dozens of rocket types. They have been used safely to launch crewed capsules. Liquid rocket engines are commercially available. (In fact, every single crewed American vehicle has had liquid fuels as their main source of energy. The SRB's on the Shuttle are booster assist and the only Gemini to fly on a solid was an unmanned test capsule).

    What we are seeing here is a departure from decades of development. Solids have been considered unsafe for manned flight for decades as they are not able to be throttled in flight. Once lit, they burn to exhaustion. They have uneven burn characteristics due to uneven mixing of the propellants. No solid casing has ever been put in a load of this magnitude. (The SRB's on the Shuttle never carried the full weight of the shuttle and they were axially loaded as opposed to have the load directly along the case). There is no engine shutdown in an SRB.

  Arguing that liquids would take a lot of development to get right is a bit misleading as it is just as much a statement to be made for SRB's.

  The whole Shuttle-derived stuff is crap. These are essentially new engines along with a new booster design and they should have had a design competition and weigh the relative merits of various design proposals. This was a fiat decision made by Griffin when he came into office. There was no technical justification. No weighing of options. Even the sizing of the Orion is extremely questionable.

Re:Solid Rocket Boosters

[khallow]

Liquid hydrogen and hypergolics (chemicals that spontaneously burn when mixed) tend to be rather dangerous for different reasons. Hydrogen leaks and can cause explosive conditions under the right concentrations. Hypoergolics often are corrosive or environmentally dangerous. For example, a popular mix is fuming nitric acid and hydrazine (which is highly toxic and can decompose releasing a lot of energy).

To this day, no one else has tried this method and its pretty advanced rocketry even forty years on. It certainly gets rid of the dangerous handling of liquid oxygen, which has to be kept ultra cool and under controlled cryogenic conditions.

Do you know how they keep LOX cold? They put a hole in the tank. The LOX slowly boils off keeping it at the desired temperature. It's warmer than liquid nitrogen, a fluid routinely handed all over the US. Its real danger is as a potent oxydizer. Many things will burn fiercely upon contact with LOX. And hydrogen peroxide gives significantly less ISP than LOX given the same fuel propellant.

The key advantages of liquid fuels over solids are several. First, the rocket can be throttled. I understand that it's possible to construct a throttlable solid rocket, but that no one has done it on a significant scale. Liquids in comparison are easy to throttle. If you need less thrust, put less propellant in the engine. Second, you can use liquid propellant to cool the engine and get better performance. Third, liquid rockets get better specific impulse than solids (that is, exhaust velocities are faster). Fourth, while some liquid propellants can decompose explosively, liquid fuels generally are much safer than solid fuel engines because the solid rockets come pre-mixed. As another poster points out, all you need is something to set the solid propellant off. Some liquid propellants, for example, sufficiently concentrated hydrogen peroxide and nitrous oxide, have similar problems, but LOX-fuel propellant pairings generally aren't that dangerous. The LOX isn't inherently explosive and you can use a stable fuel like diesel fuel, propane, or liquid hydrogen (while leaks are dangerous because one can easily get explosive condition in Earth's oxygen-rich atmosphere, hydrogen itself is stable).

For exmaple, the Solid Rocket Booster that the Space Shuttle uses, while its never been set off by accident, is a serious danger. For example, they clear the Vehicle Assembly Building when they mount the SRBs to the Shuttle. If one were to go off, I figure it'd kill everyone in the building. You don't have similar problems with liquid fuels because they fuel the Shuttle after it gets to the launch tower. Huh, there's another advantage of liquid propellants. You can insert the fuel for the rocket on the launch stand rather than in more valuable real estate like the place where the rocket is assembled.

Re:Moon landing 1969

[Bruce Perens]

With today's engineering tech - CFD software, advanced materials science,...

Well, if you exercise, has all that technology made you able to lift heavier weights than you might have in 1960? Generally not. Indeed, we are going back to the sort of design used in 1969 instead of the more sophisticated shuttle design. They had great technology for this particular problem back then. But they also had William Proxmire, architect of what is arguably the most stupid decision in the history of mankind: the turn back from pioneering space.

Bruce

Mod parent up to 6

[Shandalar]

This is a non-story. Rockets explode during their development.

Re:Only took 'em 12 years to get to THE MOON...

[framauro13]

The difference being that, at the time, the entire population rallied behind NASA. Our domination of the Space Race was needed to establish our position over the Soviets during the cold war. People had no problem allowing the government to pump money into a program that would prevent the Soviets from establishing a foothold above us in space.

Unfortunately, the population doesn't have that kind of motivation (or fear) anymore. You can damn well bet though that if al-qaeda started launching men into space and two the moon our asses would be back there by the end of the week.

'Spin offs'

[0123456]

"Link?"

I believe you'll find it's another made-up statistic to justify NASA based on 'spin offs'; most of those arguments turn out to be bogus when you actually look for proof.

In addition, if you want CCDs, you'd be better off spending the money to develop them and skipping over the entire mult-billion dollar HST thing. Now, I think the HST is a good thing, but it has to stand on its own merits, not on the basis of some possible 'spin offs'.

Re:It's simple to solve this problem

[willfe]

They need to either get this right and kill no one in the first few HUNDRED launches of the vehicle (if it's not superseded by then) or convince people that if we do incur a few deaths they are the price that has to be paid.

They've succeeded completely in the second count there -- in 120 launches, 14 human lives have been lost in two accidents (one on launch, one during reentry). Hundreds of humans have taken over a hundred trips into space on the shuttle, and the vehicle has killed only a handful of them.

political reality calling...

[Goonie]

I support the idea of nuclear rocketry, in theory.

Let's however get back from engineering dreamland and take a cold hard look at political reality. Anything with the word "nuclear" in it scares the shit out of the vast majority of people. Most people seem to be convinced that every nuclear device is a potential nuclear weapon waiting to go off, and that any nuclear accident will inevitably result in thousands of deaths and an area the size of Texas rendered uninhabitable.

I am perfectly well aware that the actual situation is nothing like that (and, furthermore, the results of a chemical rocket malfunctioning aren't pretty either). But nuclear rocketry in Earth's atmosphere is a nonstarter for the next couple of decades at least.

Thoughts from an aerospace engineer

[FleaPlus]

Over at Transterrestrial Musings aerospace engineer Rand Simberg has some pretty interesting thoughts on this issue. A quote:

http://www.transterrestrial.com/archives/010396.html#010396

What exactly is the issue? The problem is that any structure has a resonant frequency at which it naturally vibrates. If you excite the structure at that frequency, you can develop a positive-feedback system that will literally shake it apart (the Tacoma Narrows Bridge is the classic example).

Solid rocket motors don't run particularly smoothly (compared to well-designed or even poorly designed liquids) and large solid motors provide a very rough ride. Everyone who has ever ridden the Shuttle to orbit has commented on how much smoother the ride gets after staging the SRBs.

Now, one way to mitigate this is to damp it out with a large mass. The Shuttle does this by its nature, because even though it has two of the things, they are not directly attached to the orbiter--they are attached to a large external tank with one and a half million pounds of liquid propellants in it, and it can absorb a lot of the vibration. Moreover, the large mass has a frequency that doesn't resonate with the vibration.

As I understand it (and I could be wrong, and I'm not working Ares, but this is based on discussions, many off the record and all on background with insiders on the program), there is a very real concern that the upper stage on top of the SRB in "the Stick" will be excited at a resonant frequency, but that even if not, the stage will be too small to damp the vibrations of the huge SRB below.

If this is the case, there is no simple solution. You can't arbitrarily change the mass of the upper stage--that is determined by the mission requirement. Any solution is going to involve damping systems independent of the basic structure that are sure to add weight to a launch vehicle that is already, according to most reports, underperforming. Or it will involve beefing up the structure of the upper stage and the Orion itself so that they can sustain the acoustic vibration loads. In the case of the latter, it is already overweight, with low margins.

So this constitutes a major program risk, that could result in either cancellation, or a complete redesign (that no longer represents the original concept, because the problem is fundamentally intrinsic to it).

Now, let's take apart the response a little:

Thrust oscillation is...a risk. It is being reviewed, and a mitigation plan is being developed. NASA is committed to resolve this issue prior to the Ares I Project's preliminary design review, currently scheduled for late 2008.

The problem is that NASA can "commit" to resolve it until the cows come home, but if it's not resolvable, it's not resolvable. They can't rescind the laws of physics, and we're approaching a couple of anniversaries of times when they attempted to do that, with tragic results.

Now this next part is (to put it mildly) annoying:

NASA has given careful consideration to many different launch concepts (shuttle-derived, evolved expendable launch vehicle, etc.) over several years. This activity culminated with release of the Exploration Systems Architecture Study in 2005. Since then, the baseline architecture has been improved to decrease life cycle costs significantly.

NASA's analysis backs up the fact that the Ares family enables the safest, least expensive launch architecture to meet requirements for missions to the International Space Station, the moon and Mars. NASA is not contemplating alternatives to the current approach.

The problem is that NASA didn't give "careful consideration" to the previous analyses after Mike Griffin came in. As far as can be determined, all of the analysis performed under Admiral Steidle's multiple CE&R contracts, performe

Re:Apollo Called: It Wants its Saturn V Back

[maxume]

Wait, you think the shuttle is reusable?

Getting into space isn't going to get a whole lot easier or cheaper for a long time. Maybe ever. It's the physics that are the problem.

How you got modded up is beyond me

[WindBourne]

ALL of our early missiles from the 50's were liquid based. All of our space program has been liquid based. Mercury was based on Atlas. Gemini was based on Titans. Apollo used the Mighty Saturn V. ALL of these engines were liquid based. Some are kerosine/LOX, and others are Hydrogen/LOX. The main boost of the Shuttle is based on the SSME. The main boost of the Ares V will be liquid. Likewise, even spacex's engines are liquid based. The brits abanded their missles and their launch systems BECAUSE they had so many problems. Even to this day, ALL of their missiles are produced from America.

Re:Nasa

[khallow]

I see the problem here being one of opportunity cost.

This of course assumes the technology would never have been discovered if we didn't spend the initial investment; but by beating the would-be discoverer to the punch, we get the return sooner

But what technologies are discovered later because we are inefficiently allocating resources via NASA? You can say that solar cells, fuel cells, and velcro came sooner because NASA helped invent them. But NASA has been wasting money for decades. You don't see what's missing.

Re:Apollo Called: It Wants its Saturn V Back

[maxume]

It's not reusable in a good way. Sure, the same airframes go up over and over, but each retrofit is so damn expensive you almost might as well build a new one. Not to mention all the problems that a one-size-fits-all solution brings when you make HUGE.

A smaller, reusable attempt might make sense, but the reuse of the shuttles isn't any sort of big win.

Re:It's simple to solve this problem

[khallow]

In other words, these are solved by *adding mass*. In a rocket optimized for low mass and a fixed size payload (like the Ares 1 is), removing mass just isn't an option. As I understand it, the resonance mode is due to the payload, the SRB on the bottom, and the coupling between the two masses. If you cut down either one, the coupling would be able to dampen vibration more (there's less energy that needs to be dissipated). I don't know if the SRB has a sharp peak at this frequency. If the vibrations induced are broad in range, then the improved dampening is going to be more important than changing the frequency of the resonance. But going back to the original point, you can't cut back either payload or the SRB. The Ares 1 needs to launch the amount and dimensions that it currently does. and the SRB needs to get that into orbit. There may be some clever tricks for rearranging the current coupling since mass has probably already been devoted to this purpose.

Anyway, my take is that this is going to be a complex problem. They may already set aside enough to deal with the problem, but if they haven't, then it's going to be a real problem both for the Ares 1 and for vehicles like the Crew Exploration Vehicle that depend on the Ares 1.