Bad Testing Doomed NASA's Hypersonic X-43A

RobertB-DC writes "Space.com got hold of NASA's yet-to-be-released report on the June 2001 failure of the air-breathing X-43A hypersonic research vehicle, and it doesn't look good for 'Faster, Better, Cheaper'. The report refuses to single out any one contributing factor, but it cites ground testing 'inaccuracies' and 'misinterpretation' of wind tunnel data -- in particular, failure to retest the vehicle after additional heat protection was added. As noted in the original Slashdot article, the craft went out of control when the fins broke off just seconds into flight."

Comments

A ridiculous concept from the start

[topher_k]

I worked for one of the companies involved in this program, although not directly on the program itself.

Let's see, we've got a scramjet test aircraft, which will be boosted to hypersonic speeds by a modified Pegasus rocket, which will be dropped from a B-52. So, besides developing the scramjet test aircraft, an interface system between the Pegasus and the X-43A needs to be designed and the whole system tested.

That didn't bother me too much. What really got me was what the point of the program was in the first place. The goal was to test the ability of a scramjet engine to propel an aircraft at hypersonic speeds. The Pegasus booster was supposed to accelerate the test aircraft to hypersonic speeds, then detach, at which point the scramjet would be started and the instrumentation would transmit 10 seconds of data. Besides the limited amount of data, if I recall correctly, the scramjet was not supposed to even maintain the aircraft's speed, which calls into question the value of the technology as a means of propulsion, in my opinion.

If I recall, the contract value was $33 million, and was significantly overrun. Your tax dollars at work (if you're American).

Re:A ridiculous concept from the start

[sllim]

To appreciate the test you have to have a basic understanding of what the scramjet does.

A scramjet seperates the hydrogen and oxygen molecules in the atmosphere and uses the hydrogen molecules as fuel for the engine.
In doing this you have an engine that can go significantly faster, an engine that uses up a fraction of the fuel load of traditional aircraft and an aircraft that expels significantly less harmful waste in the atmosphere then a traditional jet engine.

The downside is that the engine is not physicaly capable of working until it has attained an almost rediculous speed. Something like Mach 3. The damn thing won't even light before that.

So if you have a need for an aircraft that flies faster then mach 3 then this is a goal worth striving for.

NASA (as well as other organizations) have been able to 'light up' the engine in wind tunnel tests. But as of the time this test failed (I think the Australians got it to work a few months later) no one was able to even get an engine like this to lite up outside of the labortory.

What this test was designed to achieve was simply to see if they could get the engine to function at all. They wanted to see if they could get the engine to seperate the hydrogen from the oxygen and to light up the mixture with traditional jet fuel. If you can do that then you move onto the next step.

So this test had no need of anything more then 10 seconds of data.

Re:A ridiculous concept from the start

[Moofie]

See the technology development of the gas turbine engine for many useful parallels.

Scramjets are about the most absurdly complicated things you can imagine, from a fluid dynamics standpoint. Much more data is required to refine their operation. Such data comes from programs like this one.

Now, it may be that NASA and your firm are not being as frugal as they should be, but this is useful and important research, if you think that high-speed air breathing flight is important.

(Me, I say use ballistic rockets, but what do I know?)

Re:A ridiculous concept from the start

[tengwar]

Why doesn't the concorde still fly? It burns WAY too much fuel to be profitable.

There's a Concorde flight twice daily over my house. They stop flying in October, but that's because of the cost of upcoming refits and because Airbus will not maintain them in the future. They appear to be highly profitable at the moment.

Fuel costs just aren't an issue: do the maths. An average load for a transatlantic flight is probaly about 100 passengers, paying about £5000 each for a return journey, i.e £0.25M revenue for one journey. Fuel capacity is 96 tonnes, which would cost about £9000 to fill.

Re:A ridiculous concept from the start

[Idarubicin]

To appreciate the test you have to have a basic understanding of what the scramjet does.

I agree completely. So why do you then tell us the following? You have been misled, my friend.

A scramjet seperates the hydrogen and oxygen molecules in the atmosphere and uses the hydrogen molecules as fuel for the engine. In doing this you have an engine that can go significantly faster, an engine that uses up a fraction of the fuel load of traditional aircraft and an aircraft that expels significantly less harmful waste in the atmosphere then a traditional jet engine.

Quick primer on scramjets, from the top:

In a typical jet engine (see here, for example) air enters through an intake at the front, and passes through several fan stages to compress (and heat) the incoming air. Squirt fuel into this hot air, and the rapid combustion generates exhaust at high temperature and pressure. This high pressure exhaust propels the jet (and drives a turbine which turns the fans in the compressor).

The downside of this design is that it is mechanically complex--those compression stages have large, finely-machined, rapidly-moving parts which are subject to wear, tear, and accidental failure; they also add a significant amount of weight to the engine.

Enter the ramjet. (See also cutaway figure.) Instead of using fans to compress incoming air, a ramjet uses a specially shaped inlet. Air enters the jet inlet at high speed, and then is forced through a narrow aperture. The result is compression without fans. Unfortunately, the ramjet will only work when the jet is travelling at significant speed--there isn't going to be any air coming into the engine if the aircraft isn't moving.

A scramjet is a supersonic combustion ramjet. In a plain vanilla ramjet, the incoming air is slowed while it is compressed to the point where it is travelling slower than sound. Combustion takes place in air that is still moving quite quickly, but not supersonically. Although easier to manage from an engineering standpoint, requiring subsonic combustion places an upper limit on the speed of a conventional ramjet.

The scramjet functions in a similar manner--incoming air is compressed and heated through a properly shaped inlet, then fuel is injected, and the combustion products propel the jet. The defining difference is that combustion takes place in a supersonic airflow; in practice, this dictates certain changes to the basic ramjet design. Again, the scramjet requires significant airspeed before it can be started.

Quite correctly, you note that the fuel for these beasts is often hydrogen, though in principle nearly any air-combustible liquid or gas could be used. The fuel must be supplied, however--a scramjet cannot extract hydrogen from ambient water vapour. The hydrogen scramjet is inherently no cleaner burning than any other air-breathing hydrogen engine. Given its high operating temperature, I would be quite surprised if it didn't generate significant nitrogen oxides in operation.

Knock it off people... its really angering....

[Simkin1]

First off... this is my own opinion only, and does not reflect the attitude or thoughts of my employer.... with that said:
I'm not sure whether to be pleased that someone actually took the time to locate a report that's been out for almost three months, or irritated that they (space.com) are completely misleading the public as to the cause and who's to blame for the defect (or that somehow they're privy to information that's available to everyone) which resulted in NASA having to terminate the Launch and Research Vehicle (X43A). On top of that, it's rediculous to post it to a forum like this. Reality check folks... This is a proven technology (hypersonic ram/scramjet engines) which has a large application base, and WILL provide faster, cheaper and cleaner access to space. I appreciate (not really) the folks that seem to get off on putting down NASA's achievments, or summing the work NASA does up to the moon landing (...and depending on who you listen to apparently we made that up too... -- that's sarcasm in case you didn't pick up on it.) If anyone of you has a moment to actually read the MIB report... and more over has the intellectual capacity to understand it (Lord knows no one's displayed that capability here, or at space.com), then you should understand where blame should be placed. The main portion of NASA's work was with the X-43A VEHICLE, and the subcontractor ORBITAL was supposed to provide a delivery system which would get NASA's RESEARCH VEHICLE to the test range. For those of you who can't quite put it all together, ...come on... you can do it... put 1 and 1 together... NASA straps their research vehicle to the nose of Orbitals delivery system -- the launch vehicle... OH, is the light dawning yet?... what does the report indicate is the problem? was it the hypersonic vehicle that failed?? NO MORONS, it DOESN'T say that... the VEHICLE never got to the test range!! NASA never got to TEST the friggin vehicle in the first place.

...but like always... you never hear about NASA's THOUSANDS of achievements... I'm willing to bet that most of you can't name a single thing that NASA has contributed to the US technological community...why is that? maybe it's because those achievements never get air time. Achievements aren't juicy enough for the media... Media gets more attention when it focus's on NASA's failures... When was the last time you heard a news organization extolling the virtues of NASA?
All this criticism of NASA as "incapable", or "no longer with it"... to you folks I say PISS OFF... you have no clue what you're talking about. The X-43 folks are anything but sloppy at the research they do; the managment is outstanding, and the technical expertise is the best in the world.
To folks that think that NASA is just a big bureaucracy; you're absolutely right. They are, just like any other organization that does bleeding edge research and provides outstanding technical work to the US government. Any organization that does the kind of experimental research that NASA does (look around, there aren't any) has to have a legitimate infrastructure in place to handle the costs and managment structure that large experiments have. There is NO way around this, and anyone who thinks there is, is a fool.

To those of you who doubt that the X-43A vehicle will fly... PAY ATTENTION TO WHAT HAPPENS IN THE NEWS IN OCTOBER!

Re:RTFM

[tengwar]

It's a very old urban legend. As far as I can tell, the chickecn cannon was developed in the UK to test the De Havilland Comet.

Re:Yeah, but how much are you willing to pay?

[karstux]

Apollo wasn't as expensive as you might think. According to this NASA page, total funding for the Apollo program was less than 20 billion dollars (which would equal about 100 billion of today's dollars).

In contrast to that, last year's US GDP was about USD 10 trillion. It's just a matter of will - the state's administration doesn't really have an interest in space exploration.

Re:Yeah, but how much are you willing to pay?

[SmilingBoy]

You are way off.

The total cost of the Apollo program was $19.4b.

This is the total program cost starting from 1965 (or was it 1964?) to 1972. Let's assume that the year 1969 was the year with the highest spending, say one quarter of the total sum, ie $4.9b.

The nominal GDP of the USA in the year 1969 was 3928.7b.

Therefore, at its peak, Apollo consumed approximately 0.12% of the GDP of the US.

I think you might be referring to the nuclear program during and after that World War II. That was expensive! (I've got no numbers though)

X-43 Test Failure

[De_Gopher]

I haven't seen that particular report, but just to clarify what I know, the failure wasn't in the X-43 hypersonic vehicle but in the Pegasus launch booster, built by Orbital Sciences. Apparently the Pegasus was built to be launched at 40,000 feet, however in the first test it was launched at 20,000 feet. The increased air density and aerodynamic loading at this altitude caused a structural failure in a stabilising fin on the booster, not the X-43 craft itself, which remains unproven.