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SpaceshipOne's Control Problem Fixed
Baldrson writes "Wired News reports that Rutan's team says they have gotten to the bottom of the June 21 flight anomalies that affected the first SpaceShipOne sub-orbital flight: 1) A control surface actuator had run against a stop limiting its movement, and 2) Wind shear caused the 90-degree roll shortly after rocket ignition. Rutan also said with the problems now identified, the next time SpaceShipOne flies, it will be to win the prize."
The article says that the problems were caused by:
"the actuator delayed moving one of the ship's flaps because it "had run against a stop," limiting its movement."
Isn't the WHOLE purpose of the stop to limit movement? or was the stop jarred loose and was stopping movement when it wasn't supposed to ?
Rutan's plan to have 3 flights within 2 weeks is a good idea. That way they have an even better chance of winning the prize. It's something I never thought of before.
JasonBlogs
I reckon Scaled Composites could almost make more than the value of the X-Prize if they offered those two empty seats for sale. It's almost worth starting a fake ebay auction just to see what price is reached!
Nothing is really guarenteed to be perfect. The fact that there are factors that are beyond our control and completely unpredictable means that there is always a chance that something will go wrong. Fixing it and trying to make sure it doesn't go wrong again is all fine and everything, but there is always that probability factor that we cannot detect, calculate, or control.
I am just quite glad that they had the backup system, because that is what prevented a catastrophy. If there is a x% chance that the primary system will fail, and x% that the backup will fail, combined it makes the chances of a catastrophy much lower.
I believe that if we are going to be successful at a private space race, or even any other high-risk things (Even lacking risk to human life), then redundancy and backup is definitely critical. If a few failed heat tiles can destroy a space craft and kill people, and there is no contingency plan for failed heat tiles, that is a problem. If a computer miscalculation in Metric vs English measurements can completely throw off a multibillion-dollar space probe, and there is no way to recover when the error is first detected and has not yet caused problems, then that is just not right.
I look forward to seeing if they win the prize, and I applaud them for having contingencies. If more systems had contigencies for the most critical failures, we'd possibly be much further ahead in various technologies. Let's see how this space race goes.
@Whee
NASA, on some level, is really an organization for several major and minor companies, why would it be ruled out of the prize?
Will commercializing spaceflight be a step forward for space research? Why is it that when companies step into public domain scientific fields the results are inevitably viagra when there is still no cure for cancer, aids... etc. Public grants and public institutions (Nations and Universities) are still the bedrock for pure scientifc research. I only see economic and superficial consumerism inspired by the x-prize.
What do you think?
You should have been there for the first flight. I'm amazed that they got it off at all. The winds overnight were 40+ MPH on the ground (blew over 4 of the 7 porta-potties in the campground area on the airport grounds). They calmed down for the 6:30AM launch, but it was easy to see from the contrails behind the aircraft above that there was still a lot of wind up there.
I am a pilot, albeit an ordinary private pilot and not a spaceship pilot. I began flying in the 1970s around the time that "wind shear" first started to be considered as the possible cause of certain kinds of accidents. Although the phenomenon is real, for a while it became somewhat notorious as one of those "catch all" explanations that get hauled out when someone can't really figure out what happened. So when I hear it blamed in a conclusory way for something weird, without a good explanation for why it should apply, I get skeptical.
The deal with wind shear is this. Ordinarily, airplanes move within moving masses of air and get carried along by them. This is no big deal except that it affects navigation (e.g., even though your nose is pointed north, you might really be tracking northeast because you are within a mass of air moving from west to east). Moving masses of air don't ordinarly affect the airplane in an "aerodynamic" sense because what matters is how the plane is moving relative to that mass of air, not relative to the ground. Wind shear occurs because there are often distinct boundaries between different masses of air that are moving in different directions or at different speeds. Hitting a wind shear boundary can be an issue because due to inertia (or momentum, whatever you prefer to call it), the plane does not instantly make the transition to the new conditions, so its situation changes temporarily relative to the air. But it's only scary when the extent of the change is greater than the aerodynamic limits for your airplane and your present attitude.
For example, if you are flying at just five knots above stall speed, and you hit a boundary that has an abrupt ten knot difference in the wrong direction, it can pull the rug out from under you. But if you're flying at normal cruising speed, that same difference just causes a little turbulence. So to have a critical problem with wind shear you need both factors -- being near one of your aerodynamic limits (stall speed, red line, whatever) PLUS hitting a boundary that emphasizes the change in air movement in the WRONG direction for that limit.
So the reason I am skeptical is that Rutan gives no explanation for how exactly wind shear caused the loss of control. Was the ship being operated near its stall speed? Was the wind shear differential totally huge? Was the ship in a weird attitude (high bank angle or something) that reduced its tolerance to changes in airspeed? And is there any meteorologic evidence of any big wind shear conditions at that place and time? Otherwise, it is just wishful thinking that he has an explanation for this?
This just an altitude record. Not a space flight! There's only so much you can do in suborbital. If you just want to get up there to launch a satellite, then you might as well simply use a big missile, and put the effort into recovering the lower stages.
When they manage to get to 3 times that altitude, then its time to be impressed.
I think you forgot the most important part of the development process. So my general software development proceedure tends to look more like -
;-)
1. Write code
2. Proclaim success!
3. Prof... err, wait, some bugs
4. Fix code
5. Proclaim success!
6. Prof... err, wait, some bugs
7. Customer or Management changes requirements
8. goto 1.
9. Profit!
Maybe I should debug my development methodology, seeing as I never seem to get to step 9.
The cool thing about the xprize is that it provides a fixed milestone for private companies to shoot for in a fixed timeframe.
I am a big fan of the private 'prize' process, and think that with the success of the xprize we should figure out how to offer a slew of additional prizes to continue to stimulate private space efforts.
I am somewhat surprized that there are not more prizes offered for solutions to hard problems in other areas. Seems like a cheap way for folks to get researchers motivated.
Why not start a non-profit foundation whose sole purpose is to offer bounties with well defined acceptance criteria for a whole range of technical challenges? Any philanthropic and technically oriented billionaires up for the challenge?
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
Your explanation sounds great, but, you are using the wrong frame of reference. You are considering classic wind shear at low level/low speed accident scenarios, because that's what the schools teach about. Finding a shear greater than 20 knots at low level is rare indeed. Head up to the tropopause, and it's a totally different story.
At the junction between troposphere and stratosphere is this little phenomena known as the 'jet stream'. 100 knots of shear on the boundary of the jet streams is actually 'quite normal' and 'not bad'. I've seen 150 knots of shear over a very short distance vertically (less than 2000 feet) while penetrating the jets. This is still not a huge big deal, just gets a little bumpy, but, take a good look at SS1.
At the time of the roll event, the aircraft was accelerating on the initial rocket boost. It was in transonic, or early supersonic flight regimes. Penetrating a shear layer that gives a 100 knot difference in relative airspeed would set up some very very interesting asymetric shock wave scenarios, where the shock buildup on one side of the airframe is completely different than on the other. Even if this situation is just momentary, the asymetric forces will be huge, and cause a very noticeable deviation from nominal flight path projections.
Your frame of reference for shear is 'low and slow' in 'low performance' aircraft. SS1 is a very high performance aircraft, operating 'high and fast'. The primary contributor to aerodymanic forces will be shock waves and various forms of drag they produce. It's a whole different world, and everything you learned about 'low and slow' just doesn't apply to the 'high and fast' flight regimes. The SS1 flight mode at the time of the upset was 'at or near vertical' at transonic or supersonic speeds. It would not be at all surprising to see a major upset in the craft stability if it accidently penetrated the core of a 150 knot jet during that flight condition.
At this time of year, at those lattitudes, the core of the jets would be at an altitude in the area of 45 to 55 thousand feet. It would be unusual to see a jet core that far south in June, but, not unheard of. It's to late, and i'm really not inclined to go dig up old met charts from a couple weeks back, and see what kind of jet stream cores were over that part of california that morning. Sounds to me like that's what they may have hit, and, means the meteorology guys will be watching the jet charts a LOT closer for the next launches. Wouldn't surprise me at all that they even overlooked the detail, with an attitude of 'jet stream cores, over california, in june, who are you trying to kid?'. It's common in the winter, but not in the summer.
I wouldn't really class Jon's team as close. Sure, they're definitely getting there, but the highest controlled flight they've done was only 131 feet high with a subscale model. Several of the other teams could have done the same thing and we'd never know about it - its just that Armadillo are very open about their progress.
Actually, that's one of the things I really admire about Armadillo Aerospace - they've kept very little to themselves - anybody with some money, patience and skill could get going quite quickly by learning from the Armadillo website.
I am a big fan of the private 'prize' process, and think that with the success of the xprize we should figure out how to offer a slew of additional prizes to continue to stimulate private space efforts.
I think (hope?) that once the X-Prize has been won, there will be another prize put up for the first private flight into orbit, since that's the next big milestone in commercial spaceflight. Or maybe a prize for the first suborbital space flight to the other side of the planet - there are big applications for suborbital space flight as a replacement for normal air travel since once you get our of the atmosphere going hypersonic is much easier.
I must admit that I didn't realise the prize expired at the end of this year though - that kinda puts a lot of pressure on everyone.
http://blog.nexusuk.org
"Heat shields on the other hand do a very tough job."
Not really. The Chinese reportedly used thick sheets of (admittedly chemically treated) oak on some of their early unmanned launches.
"The protective tiles on the Space Shuttle, for example, are expensive, and very fragile."
I think it's a safe bet that Rutan won't be using such tiles on SpaceShipTwo.
"Ablative heatshields are a possibility, but they do add to the per flight cost."
A properly designed ablative heatshield is much easier to remove and replace than shuttle tiles are to maintain. You just unbolt the old one, slap on the new one and you're ready to go... with tiles you have to check they're all in place, check they're all secure, and make sure there are no bumps larger than about a millimeter over the entire underside. That's a huge job, and one of the reasons why the shuttle takes so long to turn around.
(Note: ablative shields weren't really an option for the shuttle as designed, but there were a lot of other designs proposed before this one was picked).
Actually, there is a very interesting way to cool the spaceship during its descent from orbit: use the rocket fuel itself.
Why not? Cryrogenic fuels are extremely cold, and it is theoretically possible to route these cryrogenic fuels to actually cool down the spacecraft's structure during atmospheric re-entry if there is a safe way to vent the heated fuel. When Douglas Aircraft did its studies for the ROMBUS launch system in the early 1960's they actually figured out a way to use liquid hydrogen to provide heat protection during the descent. I'm sure that Burt Rutan knows about this idea and might use something like liquid methane as a rocket fuel for the ascent and as a coolant to protect the structure on Scaled Composites' Tier Two/SpaceShipTwo project.
To win the X-Prize, you have to do two flights within a 14 day period.
It's an important detail, because it means the vehicles have to be reusable with minimal refitting.
The Space Shuttle could never win the X-Prize, even if it were flying and qualified for the contest, because its turnaround time is too long.
Jon Acheson
All opinions expressed herein are my own, and not those of my employers, who are appalled.