Spaceship One Test Flight Anomolies

Marc Newman writes "Aviation Week reported that Scaled Composites had some unexpected flight anomolies on it's 23-Sept-2003 flight test. The test was conducted with an aft Center of Gravity (CG) and produced some unexpected nose up pitching. They were able to maneuver out of the stall with lateral motions. They also had much higher than expected drag from the newly installed gear doors. They described the pitch up motion as serious, as some abort scenarios leave the vehicle in an even worse aft CG situation than this flight (they can dump oxidizer but not fuel, and the fuel is located aft). They indicated that this lack of pitch control would 'require changes'. It's not expected that they will be able to meet their goal of a flight into space by the end of the year. There is a flight log and there is an article in this week's Aviation Week and Space Technology but it's not showing up on their web site yet."

Comments

Re:Anomalies you twit

[Tardigrade]

I hereby dictate "anomolies" to be an acceptable alternate spelling, if it has not yet been so dictated. Problem solved.

Re:Anomalies you twit

[OwlofCreamCheese]

I pronounce that spelling.... ano (like danno) molies (like holys) that spelling of the world is how 3 year olds say "animals".

Re:Anomalies you twit

[Anonymous Coward]

How dare you! I declare your dictation null and void. Times a thousand! NO! INFINITY!!

Bummer, but hey they still beats the shuttle.

[HenryWirz]

Assuming that they are hosed, and will miss the all important December 17th date, they are still gonna beat NASA as the next manned flight from this continent :)

I'm not a fair weather fan, I bet they still have a shot at the 17th.

Re:Bummer, but hey they still beats the shuttle.

[florescent_beige]

Re: "this continent" Not necessarily: Da Vinci and Canadian Arrow

They sho' does!

[Anonymous Coward]

they still beats the shuttle

*cringe*

The value of testing.

[LWATCDR]

This could have killed someone. This shows the value of a well thought out test program. I wonder if any other X-Prize teams are testing abort situations and CG limits?

How is this different from any other plane?

[dougmc]

All planes become very difficult to fly when the center of gravity gets too far back. (On the other hand, if the center of gravity goes too far forward, the plane becomes extremely stable, but loses maneuverability and efficiency. If it goes *too* far forward, you may not be able to even keep the nose up. But as a rule of thumb, too far forward is much better than too far back.)

If the center of gravity goes far back enough, the plane becomes unflyable. Not quite so far back, the plane may be very difficult to fly (requiring that the pilot `stay on top of it', and if it gets into a spin it may not be possible to recover from it.

Aerobatic planes and planes that are trying to make very long trips on limited fuel (like the Spirit of St. Louis) will keep the center of gravity a further back than most -- but not too far. In a trainer, you usually keep it a bit further forward than usual to enhance the stability of the plane.

How is this different than any other plane? They intentionally set the center of gravity too far back, and it flew poorly. They should have anticipated this (and I suspect they did, and this isn't as big a setback as expected.)

Re:How is this different from any other plane?

[Anonymous Coward]

Wow, I guess they don't know what they're talking about. Why don't you go and take charge of those amateurs, huh, dougmc?

Obviously they didn't expect the a/c to pitch up to the degree that it did.

Re:How is this different from any other plane?

[BigBir3d]

I am surprised that a poster with such a low ID number would resort to using logic to analyse a linked to article. I commend thee. </sarcasm>

And it happens to be that you are nearly 100% correct.

I was intrigued by the lack of understanding with respect to drag and gear door (seams I presume). Wasn't this sufficiently studied in the 1950's? *sigh* Geeks just love to learn it again for the first time I suppose... ;-)

One would hope that these new aero aids that are going to be implemented to keep the nose from coming up on its own will not be 100% necessary. What if they break, and the aircraft is in a overly loaded state? Your average space jockey (not that those exist yet) is not going to be as responsive, or understanding, as last month's test pilot was. This sounds like a dangerous path to go down. Any modern fly by wire aircraft should revert to level flight assuming most of the aero parts are intact, and the pilot is giving zero input (hands and feet off condition - as if passed out). Doesn't sound like this pig can do that. Bad design decision. Makes me think of all the other short cuts that were possibly taken.

Re:How is this different from any other plane?

[PurpleFloyd]

I take it you were there and able to see everything that went on; otherwise, of course, you would stop making such uninformed statements about the nature of aviation.

First, the "lack of understanding" about drag and the gear door is perfectly normal. If things operated identically in real life and in computer simulations, there would be no need for physical testing at all. Anomalies come out in tests and are fixed. It might well be that the door design is not at fault; perhaps the finish is rough (something that can cause trouble at very high speed). Perhaps it didn't seal properly. Whatever the cause, it will be found out and fixed. That's what the tests are there for.

As for your second point, you have absolutely no grounding in reality when you say that any modern fly-by-wire aircraft should revert to level flight when the pilot is giving zero input and some aero parts are broken. First of all, Spaceship One is not fly-by-wire, it's manually controlled for a good part of its flight. Second, with aero parts missing, no aircraft will be able to fly just as well as it can under normal conditions. While it might be possible to fly a modern aircraft under extreme conditions (like missing control surfaces) it would be extremely difficult and not simply handled by the computer.

Burt Rutan is famous for building safe and reliable aircraft; I doubt that he will take shortcuts when it comes to safety.

Re:How is this different from any other plane?

[DAldredge]

I miss the days when a 4 digit /. id was a new account...

Re:How is this different from any other plane?

[BigBir3d]

I take it you do not know what "fly-by-wire" is. In a nutshell, the computers take the pilots input, interpret it based on the given conditions, and apply those inputs as the computer thinks the pilot intended. This is supposed to compensate for unintended minute movements pilots transmit through the controls in flight, especially in high stress situations (first real applications being military of course). "Fly-by-wire" does not imply auto-pilot as you seem to suggest (manually controlled).

As to aero parts missing, I was referring to the add-ons the program needs to get the nose back down. BS stuff that is kludged on later very rarely is as robust as the rest of the design (ask any programmer on /. about that one).

Re:How is this different from any other plane?

[kinnell]

I am not an aerospace engineer, but even I know that all the simulation, wind tunnel tests and design experience is not enough to guarantee that you can get a plane right first time. This is why they build prototypes and put them through rigorous flight trials before deciding that they are ready to fly.

They obviously have a requirement for how far back the centre of gravity can be, flew a test flight to check this requirement and it failed, so they fix the problem and build a new prototype. This is no different to any other aerospace project. Implying that they are incompetent because of this is both arrogant and uninformed.

Re:How is this different from any other plane?

[PurpleFloyd]

No, fly-by-wire is simply the replacement of direct physical linkages (via wires, hydraulics, etc) between cockpit controls and control surfaces by electronic sensors at the cockpit end and actuators (like, say, servos) at the control surface end. While it's trivial to route those signals through a computer for processing, that's not always done. In fact, you seem to think that fly-by-wire implies autopilot; your previous statement that a FBW aircraft should return to straight, level flight if no control input is given sort of assumes that an autopilot is present.

As for aero parts being "kludged on" later, you seem to have no understanding of how parts are attached to the airframe. Assuming that this problem actually needs aerodynamic modifications, (it might be solvable by simply shifting internal weight) those modifications will be attached directly to the frame. They won't just be pop-riveted to the skin or something. In any aircraft, if parts start falling off, conditions are already so bad that you probably are screaming for dear life or are already dead. While modifications to the original design might not be as efficient as a completely new design, they will still be air- and spaceworthy. Scaled Composites has invested millions into developing a working space vehicle; they're not about to throw all that away by slapping poorly thought-out modifications onto Spaceship 1 and calling it good.

Re:How is this different from any other plane?

[BigBir3d]

1. In general. Yes, this is Airbus, and yes, this is the general accepted terminology for what fly by wire is.

2. SC is not going to be doing a ground up redesign of Spaceship 1. There is only one reason for that; it is a race. They want to win. Shortcuts have been taken, and will continue to be taken. No, aero parts won't be pop riveted on (I am not as stupid as you want to assume), but these new parts will exert stress' on the airframe, as well as the outer skin of this vehicle. Obviously the engineers that designed this vehicle did not take into account certain testing procedures (shortcut by them, or by mgmt in not telling them what was to be done, or not mgmt knowing what was to be done when they {engineers} were in the design phase).

It is expensive to do this right. A plan is required. A plan includes more than just a goal and a general idea of how to achieve said goal. There are many different ways to achieve low orbit "space" flight. Just in launch techniques (rocket off the ground, tow, piggy-back, etc) you can do things many different ways. It's not just design a ship, figure out how to launch it and then test it. You have to know where you are, where you want to go, and how and when it should be done. Not to mention contingency plans for failures at any given point.

This being a race and all... I am certain that this has not been done. This is what scares the hell out of me wrt civilian space flight. Wild west seat of the pants just doesn't cut it. But I am sure you knew that ;-)

Re:How is this different from any other plane?

[Ice Tiger]

And I just missed those days.

Hybrid Engine

[pfdietz]

I bet they're regreting going with the hybrid engine. A pressure-fed liquid engine would have
enabled them to dump all propellant in an abort.

Re:Hybrid Engine

[the Llama of Virtue]

Not really. You would still have to pump the fuel and oxidizer through the engine, and in order for the turbopumps to pump the engine would have to be running (both systems are interconnected). So in short, no purge for you! Depending on the design of their hybrid, position of the nitrous tank will be key, as the nitrous oxide tank will deplete, mass-wise, quicker than the HTBP (rubber), resulting in a CG shift to the rear of the spacecraft. -philski aerospace engineer in the making

Re:Hybrid Engine

[Anonymous Coward]

What turbopumps? The hybrid engine is pressure fed, and so would be an all-liquid engine that would replace it. Pressure-fed engines have no pumps.

Low ID number? Come on...

[marcus]

Give me a break. ;-)

Re:Low ID number? Come on...

[PhuCknuT]

Mine's lower :P

Re:Low ID number? Come on...

[Bloater]

I don't even know how big mine is, I haven't seen it since the accident.

Burt Rutan may be famous for building safe....

[Schwarzchild]

...planes but what's up with his believing that aliens built the pyramids in Egypt? I couldn't believe my eyes when I read that in Wired magazine. The writer must've misquoted him.

IF there were no problems at all

[Zachary Kessin]

If there were no problems at all in testing I would be worried. Burt Rutan is pushing the limit here. When you do that you should hit a few snags. Its not a bit deal that is why you do a lot of flight testing. If you look at the test logs it is very clear that Rutan et al have a well thought out flight test program. And they are running it. From everything I know they have people who really know their stuff.

They will fix this problem, and I'm sure they will find a bunch of other ones and then they will fix them too. If i were a betting man (and I'm not) I would be putting my money on scaled to win the X-prize.

Re:Bummer, but hey they'll still beat the shuttle.

[HenryWirz]

I meant what I said and I said what I meant.

The Da Vinci team is currently looking for Aerospace engineers and technicians. They've got nothing but a cool fiberglass mockup and a launch site.

Canadian Arrow seems to be stalled building their engine. They do have Astronauts, however.

Rutan has Astronauts, Engineers, and the FAA will give him his launch site or he said he's gonna launch from Mexico. Oh and he also has a working space craft. Give or take a trim problem or two.

Flight testing like this is not new

[Buran]

The flight tests at this point are comparable to the ALT (approach and landing test) program that was flown from about 1977 until 1979 using an unpowered glider-only version of the Space Shuttle -- it had fake engine nozzles, no real tiles, and had fake tile patterns to make it look mostly like the real thing (presumably this is painted on; I haven't seen Enterprise in person yet, but will late this year or early next). (The imagery of it in the introduction to the TV series of the same name is incorrect -- the name is in the wrong place, and the "tile" color pattern is completely incorrect and should only be found on space-capable orbiters, so I think the photo was created by digitally placing the Enterprise name onto a photo of one of the other orbiters.)

This vehicle is better known as OV-101 Enterprise, and the carrier aircraft was a Boeing 747 once owned by American Airlines (at that time, if one looked at it from the right angle, "American" could still be seen on the fuselage. It's since been repainted white with a blue stripe at window level.)

The ALT program followed much the same pattern as the SS1 tests: first, unmanned captive carry flights, then manned captive carry flights, then manned glide flights (some without a tailcone, some with.) At no point were any engines ignited, and in fact no real engines were ever fitted, although the vehicle was weighted to behave like the real thing.

On the fifth drop test, an oscillation problem was found in the flight controls that caused Enterprise to wobble drunkenly upon final approach and land rather hard. This was investigated further with a fly-by-wire F-8 and fixed for the first flight of a space-qualified Shuttle, two years later in 1981. Thus, it is to be expected that problems will be uncovered in glide testing (which is the point). I think a powered manned suborbital flight will be possible within a year from now -- provided no other major problems are uncovered.