Suborbital Spaceflight Update

HobbySpacer writes "Burt Rutan's group has fixed a problem with the SpaceShipOne and recently carried out a successful drop test. Ground studies involved tests with CFD - "creative Ford driving" using a Ford-250 pickup truck. Other suborbital news includes the announcement of plans to follow the X PRIZE competition with an annual X PRIZE Cup event in which rocket teams will compete in an air show type format. In Japan the RVT (Reusable Vehicle Test) just completed its third short hop (in Japanese) within a week. (English reports on the first and second flights.) The liquid hydrogen/liquid oxygen powered vehicle seeks to develop robust, reusable technologies for vertical takeoff and landing rockets. It and subsequent vehicles will gradually expand the flight envelope to high altitudes."

Comments

Gee, officer . . .

[PIPBoy3000]

I wasn't speeding, I was using CFD!

Interval technologies in use?

[192939495969798999]

Does anyone know if there are X-prize entries using interval technology for in-flight computations or other important calculations?

Re:Interval technologies in use?

[pmz]

What is interval technology? Is it anything like interval training for athletes (i.e. number crunching really hard for short durations)?

Re:Interval technologies in use?

[johnny6vasquez]

He means systems like interval arithmetic whereby you represent a Real number as an interval bounded by two machine floating point numbers.

Re:Interval technologies in use?

[TigerNut]

Unless that arithmetic scheme was implementable using significantly less computer hardware, there would be zero benefit in doing so, other than out of theoretical interest, and unless I've misread the X-prize intent, they're not going for "the space vehicle that uses the most obscure mathematical concepts for flight control".

Re:Interval technologies in use?

[johnny6vasquez]

Yes, it's a very useful field.

Say you have an optimization problem that gives you too many solutions to evaluate with conventional numerical methods. Take for example an oil refinery that wishes to find the very best efficient and safe way of refining oil. There are many variables, equations, and nasty loop back cycles in this process. Traditional numerical analysis using floating point arithmetic will be struggling with errors carried over from each stage of the process, and will usually only find solutions near by to where you told it to start.

With interval arithmetic (and constraint processing) you will know that your answers are always correct. Any uncertainty will simply be reflected in a wider interval to contain the Real that is being approximated, the worst case being [-inf, inf].

Dr. Maarten van Emden over at the University of Victoria has a nice introduction page to the subject here at:. That is one of his current areas of research.

Here is a little quote also taken from Dr. van Emden.

"While this may seem to be of only theoretical interest, it is not. If one wants to solve systems of nonlinear inequalities or perform global optimization with side conditions of that form, interval constraints are more effective than conventional numerical methods."Quote source:

Re:Interval technologies in use?

[johnny6vasquez]

Yes, I agree that it will be a long time before we see any of this stuff running a real-time flight control system. A more reasonable line of questioning might be "Was any of the modelling software used by Rutan's group based on Interval Arithmetic?"

For the record, while real-time systems may be a while off, there are several companies offering good commercial modeling software that are built on these concepts. The reason they aren't widely known is that they are used mostly by heavy industries like mining and oil companies.

Again (see other post in thread), I offer this link to Dr. van Emden's intro to the subject here at. I direct your attention to the "How" section that lists a few commercial products.

Re:Interval technologies in use?

[Overzeetop]

My question would be, how much effort (processing) does it take to get a result which falls within the bounds (-acceptable,acceptable) or within the band for numerically processed data? I mean, if you plot a course back to earth and the landing interval is calculated as (-5000', 1000') for your zero rate of decent altitude, is that really comforting?

Re:Interval technologies in use?

[johnny6vasquez]

Not that much.

The way it works is that you set your acceptable bounds as one of the constraints that you feed to the solver. So if you may have an altitude constraint that is very narrow, while other constraints are looser.

Starting intervals:
x = [-250', 4000']
y = [300', 700']
z = [1', 3']

Where z is the altitude with respect to the landing field and x and y are the locations.

The solver will immediately throw away any answers that don't fit in those intervals and concentrate on finding the best solutions within those bounds.

Sub orbital flight

[stratjakt]

Now technically, when I was a kid, and we'd build the big ramp at the bottom of the ravine, and I'd get probably 8 feet in the air on my BMX - was that not "suborbital" flight?

Re:Sub orbital flight

[kfg]

Assuming your ravine was on earth yes, but you failed to specify. Sloppy work.

If, for instance, your ravine were on Phobos you could have gone orbital with pedaling (which again you didn't specify). Be careful though, escape velocity is only about 22.5 mph, although the high cadence the average BMX bike requires to achieve that sort of speed would protect just about everybody but track racers.

A very low orbit could be achieved at only several mph.

"Duck Timmy! Joey's coming 'round again."

KFG

Flying subs

[oniony]

Hmm, I guess "suborbital flight" has nothing to do with flying submarines then. Shame, that was such a great image in my head.

Re:CFD, for the curious

[sean23007]

"Fluid" isn't really that misleading, considering the fact that gases in this case have fluid properties. The term is scientifically correct.

Suborbital

[powerlord]

Okay, This just occured to me but, they haven't tested the engines yet, and the X-Prise is supposed to place them into sub-orbital. How close are they going to be to have to deal with re-entry? (ie. could one of the teams accidentally "over-achieve"?)

While I doubt this will happen, I'm just wondering what sort of margin for error exists.

Re:Suborbital

[oniony]

I'd imagine that, as none of the rockets have been designed for orbital flight(?), they won't stand up to the stresses of exit/reentry and will simply disintegrate. It takes a whole lot of design to get a rocket in one piece through those strains.

Re:Suborbital

[fredmosby]

Some of the flights of the X-15 had problems with bouncing off of the atmosphere, and the flight plan for space ship one is almost exactly the same. So they probably do have to worry about re-entry to some extent.

Re:Suborbital

[Carnildo]

Nothing is mentioned about static testing of the engine; what the article talks about is that in-flight ignition of the engine hasn't been tested yet. I'd assume that whoever's making the engine has done plenty of static (test-stand) testing.

Re:Suborbital

[powerlord]

Thanks. Should be interesting.

BTW, your link was out of date. The closest I could find was this: http://www.dfrc.nasa.gov/Newsroom/FactSheets/FS-05 2-DFRC.html.

Re:Suborbital

[confused one]

They have tested the engines, on the ground. It's not very likely they'll go "too far" because they're just not carrying enough fuel.

Re:Suborbital

[Egotistical Rant]

The bulk of the heat of orbital reentry stems from the tangiental velocity (motion 'parallel' to the ground) that's necessary to maintain orbit in the first place. The suborbital flights lack this component...conceptually we can think of them as flying straight up and dropping straight down (in reality there's some downrange distance, but it's modest, obviously, compared to an orbital flight)...so the only heat to be dissipated is from the craft's nearly unimpeded downward acceleration in the uppermost atmosphere as it drops into progressively thicker air.

Terminal velocity will vary with each vehicle design and flight plan, but in all cases will be less than the tangiental velocity of an orbiting craft.

It will be toasty no doubt, but not so much as to require the use of exotic materials (thermal tiles as on the Shuttle, etc.)

Re:Suborbital

[henley]

There's probably a technical specification of re-entry, but a good working definition is "A manoever re-encountering significant aerodynamic effects occuring at hypersonic(ish) speeds". You'll note the fudge-factor on speed there.

To paraphrase this: It's not the height you get to, it's the speed at which you re-encounter the sensible atmosphere.

In the case of the X-prize contenders, they'll all pretty much have to "re-enter" the atmosphere even though they're sub-orbital: anything using a rocket to get to the height required for the X-Prize (100km I think?) is going to have to be going relatively fast to achieve this; SpaceShipOne is planning a maximum speed of Mach 3ish IIRC. Thus, they'll all be hitting the atmosphere fast enough to encounter significant aerodynamic heating. Fortunately for them, they won't be doing it for long or too severely: the feathered flight mode effectively turns the whole fuselage into an airbrake, which not only bleeds speed off quickly (reducing total heat load) but also spreads the heated area across the whole base of the craft (reducing specific heat input in Watts/Square Metre or whatever your preferred power/area units are!). All this means that SpaceShipOne can get away with a fairly limited Thermal Protection System. Compare and Contrast with Shuttle's extensive, expensive, fragile TPS or Apollo's use-once-and-throw-away ablative heatshield TPS.

Note that your reasoning for worrying is slightly OTT: The difference between X-Prize sub-orbital flight and Shuttle-type orbital flight is ~Mach3 vs ~Mach25. That's quite an "over-achievement" to be hoping for, I'm afraid (and, since total heat energy input scales better than linearly with increasing speed, such a craft "over-achieving" could expect a very short and glorious career as a fireball).

Re:Suborbital

[homer_ca]

How close are they going to be to have to deal with re-entry? (ie. could one of the teams accidentally "over-achieve"?)

Not any more than you could floor the gas in your minivan merging onto the freeway and accidentally break the sound barrier. Low earth orbit needs a speed of 18000 mph or else you fall back to earth. These X-Prize entries aren't even close. Performance will be close to the X-15 rocket plane of the 60s. That set records of 4000 mph and 62 mi altitude (not on the same flight).

Re:Suborbital

[henley]

OOOh, I'm going to blow karma on a pedantry trip

Technically speaking, the only way to "Bounce off" the atmosphere is if you're coming in at greater than earth's escape velocity. If you're travelling slower than escape velocity, the best you can manage is a "loft" that trades height for speed. The golden rule here is: Once your non-interplanetary vehicle encounters the sensible atmosphere, your time in orbit is just about over.

The only vehicles for which "Bounce" was a serious problem were the Apollo capsules and Russia's Zond lunar spacecraft (which never flew manned). In the case of Apollo, "Skipping" was a serious consideration since although the trajectories ensured that even at lunar-reentry speeds, the atmosphere would be re-encountered, this could take 2-3 days on a looonggg orbit - a problem when the Command Module held power, fuel and other consumables for only 2-3 hours independent flight (having ditched the Service Module at this point). The re-entry programs and manual reversion procedures thus focussed on ensuring that a skip absolutely did not happen, at the expense of a hard ride down and loss of targetting, if necessary.

In the case of the X-15, however, the problems were different although related. Because the X-15 only got up to about Mach 6 (remembering that even low-earth orbit requires a speed of Mach 25), there was never any question of performing a significant "Bounce". Nevertheless, the conditions on an X-15 re-entry were severe enough that a Thermal Protection System (TPS) was required. Problem was, this was designed for the X-15's original target speed of Mach 5 and used a "heat-sink" inconel structure to absorb the heat whilst retaining strength. This worked just about OK, however when the X-15-A2 mods were made (external fuel tanks to increase deltaV hence re-entry speeds), this increase was enough to overload the TPS. The solution attempted was to spray a coating of (pink) ablative material over the X-15 before each flight, and let it burn off during re-entry. This proved problematic, not least of all because the charring ablative coated the pilot's windscreen! A more serious problem was caused by an experiment attached to the lower ventral fin, a mock-up of a hypersonic ramjet. At the increased speeds encountered by the X-15-A2, the shock waves from this ramjet impinged on the lower fin (rather than streaming past) and caused sufficient local heating to "eat" away the fin's structure.

Whilst it may be tempting to assign all of these problems to the "should have known better" category, remember that A) The X-15 was designed in the '50s. Using slide-rules and paper, and best judgement rather than fancy-dancy CFD codes and CAD/CAM. B) The X is important: it means that it's a vehicle designed to find out what the issues and problems are with a particular flight regime, and to test potential solutions.

SpaceShipOne's flight program is similar to the X-15 in many respects, but is lower-energy (Mach3 vs Mach5-7). They can expect to see greatly reduced heat load problems during their re-entry profile because of this, as well as having a novel way of dealing with it in a controlled fashion.

Re:Suborbital

[Thagg]

It takes about 8 times as much energy to get into orbit as it does to achieve the X-Prize parameters. You can't go that far wrong.

Still, you do have to worry about re-entry heating, even at "only" Mach 3.5. Rutan's ship will have an ablative coating that sublimates away, carrying heat, for the hottest parts of the trip -- Rutan's ship needs this as it is made of composites that cannot tolerate even moderately high temperatures. This ablative coating would be applied every flight. The X-15 used a similar coating for its highest speed flights. As others note, the X-15 flight profile is very similar the profile for Rutan's SpaceShip 1.

The Armadillo aerospace vehicle uses aluminum, and is massive enough that there is enough of a heat sink that it won't get too hot for the short time there is significant aerodynamic heating.

thad

Re:Suborbital

[fredmosby]

Actually the highest the X-15 went was 67 miles. In order to win the x-prize a craft would have to go above 62 miles, so Space Ship One would still have to go almost as high. The X-15 reached speeds of Mach 6.7 in level flight, but on parabolic trajectories for high altitude flights it didn't go much above Mach 3.

Re:Suborbital

[fredmosby]

Actually I was wrong about it's speed on reentry. The X-15 reentered at around Mach 5.5. According to Rutan Space Ship One will re-enter at Mach 3.5. I guess that's because it creates more drag.

Re:Suborbital

[acre]

Actually the Space Shuttle does have to worry about skipout. Any vehicle traveling faster than orbital velocity has to worry about it. The difference between the Space Shuttle and Apollo is the consequence of skipping out. If an Apollo capsule skips out it bounces off the atmosphere and flys past the earth and probably ends up in orbit around the sun. If the Shuttle skips out it ends up stuck in earth orbit, which is just as bad because it does not carry enough deorbit gas to do another deorbit burn. It will eventually come down in an uncontrolled manner, but not until after they have run out of power and air.

Now a little about re-entry: There are 2 thermal problems to worry about during re-entry. Heat Load and Heat Rate. The best way to think of these are maximum temperature and length of time at high temperature. If you come back from orbit at too steep of an angle you get too hot. If you come back too shallow you are hot for too long, or you skip out. In the first case you burn off the wings, in the second case you melt the structure under the thermal protection, in the third case you don't get home.

The Space Shuttle targets an entry that is a balance between heat rate and heat load (called a thermal trade off line). This is why after the Columbia accident they said that they would have had a hard time targeting a more benign entry. If they had come in steeper they would have burned up the tiles, if they had come in shallower they would have melted the wing structure.

As far as X-Prize entries are concerned, they really don't have to worry much about time at temperature because their entries are going to be rathar short. So their thermal protection just has to handle the max temp that they will get due to the aerodynamic heating, which is much less than the heating the Space Shuttle sees during entry.

Re:Suborbital

[henley]

Actually the Space Shuttle does have to worry about skipout. Any vehicle traveling faster than orbital velocity has to worry about it.

Errr.... Self-contradiction here?

The Shuttle, by definition and design, never exceeds orbital velocity. And I stand by my original assertion: Once the shuttle touches atmosphere, it's coming down soon, and it's only a matter of where and how. "Skip-Out" in this case can only be for a fraction of an orbit, because by definition once you've encountered atmospheric drag you'll have reduced your velocity below that required to maintain your current orbit. For the Shuttle, this won't present a consumables issue, although it might present control issues.

Your explanation of the difference between heating loads and rates is useful, but misses the point. With a "dense", unpowered vehicle like the Shuttle, your options for descent are limited: you need to get deep enough into the atmosphere to generate sufficent aerodynamic lift in order to maintain altitude whilst bleeding off speed (reducing your heating rate), but not so deep as to generate enough friction to overload the TPS. In fact, the TPS HAS to be designed to cope with this heating rate since that's going to be the minimum possible. Your other options are to lower the wing-loading of the vehicle (by reducing total mass or increasing wing area) which would allow you to slow down higher in the atmosphere at a lower rate. Interestingly, the total heat load would be roughly similar from such a tradeoff, but the rate would be lower. Lower/Faster descents do reduce the total heat load on the airframe, but at the expense of vastly greater heating rates, far beyond the ability of the TPS to cope. It's this tradeoff between heating rate and aerodynamic control (i.e. lift!) that drives the Shuttle's descent profile, rather than a need to minimise total heat load (because your vehicle configuration pretty much decides this).

Re:CFD, for the curious

[tlovie]

The 'Fluid' is slightly misleading.

Not to nitpick here, but 'Fluid' is not misleading at all. The common definition of a fluid is a substance that will take the shape of its container. Both liquids and gasses will do this.

who tends to fund these projects?

[rizzn]

I've been a consultant for an aircraft project for about eight years, and one of the problems we've run into over and over again is funding. Whenever an aerospace idea tries to break the mold or move from traditionally taught ideas, it seems it's generally shunned by the aerospace community. Looking at the pictures shown on their site, they are some fairly fanciful designs -- ones that certainly wouldn't be looked at from the aerospace circles we run in. So who exactly funds these projects, private investors, companies?

Re:who tends to fund these projects?

[Carnildo]

IIRC, John Caramack is funding the Armadillo Aerospace effort out of his own pockets. Burt Rutan, of SpaceShipOne, is a noted airplane designer and could be either self-funding the effort, or using his name to get funding. I don't know about the other attempts.

Re:who tends to fund these projects?

[Michael Crutcher]

I don't think anyone knows for sure but Paul Allen is speculated to be the backer behind Rutan. The article goes on to say that Internet tycoon types with entirely too much money on their hands seem to be the primary funders of this kind of thing.

Re:who tends to fund these projects?

[LWATCDR]

How does Rutan get funding? He is Burt Rutan. He has a proven track record. There are THOUSANDS of his Airplanes flying. If you look at all the VariEzes, Long Ezes, Quickies, Q2s, and even Nat Puffer pays him a royalty on his designs. Add in all the work he has done for NASA, and the DOD and he has one heck of a track record.
As far as the Aerospce circles you run in not looking at Rutan's seriously what freaking circle is that. The man has done work for NASA, Northrop, and Boeing!!!
Has your group built anything that flys yet? Carries a useful load?
Rutan built a plane that carried two people around the world on one tank of gas. In most Aerospace circles his is the Man!!.

Re:who tends to fund these projects?

[twiddlingbits]

Rutan has a pool of private investors, but he has put a lot of his own money in to it as well. I have not heard a cost estimate but its not cheap even though there are not a lot of folks on the payroll. There are some very good retired aero engineers from industry who help out for very little or nothing. Rutan has a track record of success which is why he gets enough funding to actually make progress towards the prize.

Re:who tends to fund these projects?

[rizzn]

Well, I might as well qualify my statements with the following: I'm not an aerospace engineer. I'm simply a software developer, and I know little about the politics of the aerospace industry, I simply know what the experts in the company tell me about. The chief engineers in the company have a very successful track record at Lockheed, Raytheon and other defense contractors. They aren't superstars, like Rutan is apparently, but they are competent inventors and engineers.

Re:who tends to fund these projects?

[rizzn]

In answer to your other questions, yes. Without going into the long pitch and dissertation on the whole project, what we do is tried and proven technology applied in a very innovative manner. The prototype built in 1999 proved the concept, but our backers were based out of the WTC, and had to pull out in 2001. We are currently seeking alternative sources of funding, but there are a lot of politics that honestly blow my mind when working in defense contracting circles. At this point, we are attempting to seek funding from foreign US allied governments with slightly more success.

Re:who tends to fund these projects?

[Thagg]

Burt Rutan's X-Prize vehicle is being funded by an anonymous donor. The expected final cost is around $20M, somewhat more than the $10M prize if Spaceship 1 actually wins the contest.

Note too that Rutan has been involved in space work before. The wing and tail surfaces of the Pegasus orbital launch vehicle are built by Rutan, as was the aeroshell of the DC-X vertical takeoff/landing test vehicle.

Rutan is also working on something called RASCAL, a grown-up version of the X-Prize system. It uses four large military turbojet engines to get up to Mach 3.5, in a very similar flight profile to SpaceShip 1, to act as the first stage of an orbital launcher. He intends to get Mach 3.5 performance out of normal turbojets at very high altitudes by using water and LOX injection, a concept that has been around since the late 50's, but one that nobody has put into practice.

thad

Re:who tends to fund these projects?

[FroMan]

He intends to get Mach 3.5 performance out of normal turbojets at very high altitudes by using water and LOX injection, a concept that has been around since the late 50's, but one that nobody has put into practice.

There is a bagel joke in here somewhere...

Re:who tends to fund these projects?

[LWATCDR]

You said the key word. They are not superstars. They may be good and even have good track records but they do not have Rutan's track record. I rember the first time I ever heard of Rutan. I think I was was in third grade and Popular Science had an artical on his Vari-Eze Prototype. It could haul two people at over 170 mph using a VW engine. He later up motored to an 0-200 100 hp motor. Rutan did not become a superstar over night. It took years and years of work.
Since I am not in aerospace at all and I know of Burt Rutan I find it odd that you did not know of him. That is like someone working in computers no knowing who Bill Gates is.

Re:who tends to fund these projects?

[rizzn]

Like I said before, I am not an aerospace engineer. I'm primarily a software engineer. The aerospace project I refer to is something I moonlight with. My role in the project has very little to do with aerospace, and more to do with the software side of the computer systems onboard, and some of the business management aspects. Hence I know a whole lot about my corner of the world in UAVs and flight director software, but very little outside of it. (take a look at my resume to see what my background is -- I generally don't even list this project since it hasn't gone into production yet).

Its easy to get into space heres how.

[Anonymous Coward]

1. Have you amateur astronaut strap on a life support system (scuba gear)
2. Outfit him with a controlled reentry device (parachute)
3. Put him a lunch vehicle (catapult).
4. PROFIT.

Re:Its easy to get into space heres how.

[Lumpy]

3. Put him a lunch vehicle

if you do that he will exceed the weight limits quickly!

Re:Its easy to get into space heres how.

[anto]

As a simple bonus hint - using scuba gear to provide Life Support has a few minor issues. Mostly scuba regulators are carefully designed to provide the gas from the tank to the user at the pressure of the surrounding enviroment. Which is really useful for diving deep under the water (where deep is actually incredibly shallow) but incredibly useless for trying to breathe in a no-atmosphere enviroment.

As an aside it is a truly weird feeling beeing 18 meters under the water & trying to convince your brain that you can't just swim to the surface (at least not without serious medical-type issues)

"airshow type format"

[JUSTONEMORELATTE]

Ummm, yeah. Let's increase interest in the field by following in the footsteps of airshows
What could possibly go wrong with such a plan?

--

Re:"airshow type format"

[delcielo]

Secretly, isn't that part of why you go to an airshow?

Re:"airshow type format"

[JUSTONEMORELATTE]

Secretly, isn't that part of why you go to an airshow?
Then how about we just say "NASCAR(tm)-type format" and be up-front about it?

--

Japanese space program

[Julian Morrison]

Next they ought to combine efforts with these people, and with these folks to set up a recruitment program for pilots...

How would NASA handle this problem

[HenryWirz]

If NASA had this problem they would have had to build a Wind Tunnel and finance the development of a Supercomputer, in the "correct" congressional district. Ensuring future funding of the program.

The F150 solution goes to show what the private sector can do, given the proper motivation.

Rutan is gonna win this thing on December 17th.

Re:CFD, for the curious

[Carnildo]

CFD can also (theoretically) handle solid fluids, but I don't know of anyone who's tried this.

Sined, sealed, delivered.

[TheRealFixer]

Ground studies involved tests with CFD - "creative Ford driving" using a Ford-250 pickup truck.

Why am I having flashbacks to Buckaroo Bonzai?

Re:Sined, sealed, delivered.

[JUSTONEMORELATTE]

Why am I having flashbacks to Buckaroo Bonzai?
I'll tell you later....

--

Re:Sined, sealed, delivered.

[Ours]

"Buckaroo Bonzai" I think you ment Buckaroo Banzai. Neurosurgeon and rock star, not the small trees :-).

Re:CFD, for the curious

[Thagg]

Burt Rutan has used truck-mounted systems for years to do the equivalent of wind-tunnel tests. It makes a tremendous amount of sense, mostly because it is super cheap.

To build a wind tunnel to test a full-scale airplane would cost tens of millions of dollars. The tunnels at Nasa Ames in Mountain View have been shut down because it's too expensive to run them -- to run the fans in the 120x80 tunnel took more than 100 megawatts.

On the other hand, driving a truck down the runway will generate the same windspeeds over the airplane using about 100 horsepower or about 75 kilowatts, more than 1000 times as efficient.

Burt's early van-based systems for testing the VariEze used very cute aerodynamic balances to measure the forces on the airplane models. In pictures I've seen he had a model on one side of a pivot, and a circular disk on the other side. The circular disk generates a known amount of drag, and by moving it closer and further from the pivot will show how much drag/lift/whatever the model was generating.

Disclaimer -- I tried but failed to name my son Elbert.

thad

Air show type event

[JamesD_UK]

My favourite part of any airshow has always been the static display. This doesn't bode well for the X-Prise :-)

I've seen this before somewhere

[CaptainCarrot]

Is it just me, or does that Japanese vehicle look a lot like the McDonnell-Douglas DC-X they were experimenting with a few years ago?

I work for a competitor, but I've always regretted the DC-X getting its funding cut. It looked like it was a truly innovative idea and had a lot of promise.

Re:I've seen this before somewhere

[Tackhead]

> Is it just me, or does that Japanese vehicle look a lot like the McDonnell-Douglas DC-X they were experimenting with a few years ago?

It sure does.

I'm not in the aerospace industry, but I'm damn glad to see the DC-X concept getting a second shot at life.

Re:I've seen this before somewhere

[Moofie]

Will somebody please explain to me why rocket-borne landing is a win on a planet where wings and parachutes work really, really well?

I thought the DC-X was a neat technology demonstrator, and a catastrophically broken idea for a spacecraft.

Re:I've seen this before somewhere

[red floyd]

Because wings are dead weight that need to be hauled into orbit.

Of course, the fuel for landing could be considered dead weight, too...

Disclaimer: IANARS (I am not a rocket scientist).

Re:I've seen this before somewhere

[Moofie]

As you have surmised, the fuel for landing is dead weight. Now, if you were a rocket scientist, you'd know that you need way, way, way, way, way, way more fuel mass than wing mass.

No diss, but I know a bit about this stuff. I hope that somebody who knows more than me can explain this to me.

Frankly, I don't think they can, because I think it's an attempt to be Flash Gordon rather than to make a good spaceship.

Re:I've seen this before somewhere

[fredmosby]

Maybe they figure that fuel is relatively cheep. So it's easier to just make the rocket bigger rather than add more equipment. Of coarse making larger rockets work is more difficult, but that's the only thing I can think of.

Re:I've seen this before somewhere

[Moofie]

*sigh*

You're wrong too.

For every pound of fuel you want to use for landing, you need about four pounds of fuel to get that pound of landing fuel up into orbit. If I wanted to look at the orbital mechanics text that is two feet behind and one foot above my head, I could in about five minutes derive the actual fuel consumption curves based on estimated exhaust velocities of chemical rockets.

As with all aspects of aviation, material cost is not the primary factor. Weight is. This is far more true for rocketry even than for aviation.

Why else do you think that composite and/or titanium structures, which are vastly more expensive but somewhat lighter than aluminum structures, are so widely used in aerospace?

Re:I've seen this before somewhere

[lommer]

I think the idea is that it would be a craft that would work equally well on earth, mars, or even the moon, virtually irrespective of the differences in atmosphere or, in the case of the moon, the complete absence of it.

But then again, I can't really see how we're at the point where we need a universally usable vehicle. I think we're still inexperienced enough in space that we should be using vehicles that are custom designed for each mission, so even my above explanation doesn't really make a whole lot sense. So yeah, I'd like to know the answer too...

Re:I've seen this before somewhere

[fredmosby]

Yeah, but when you take into account the extra fuel necessary to lift landing fuel into space, how much would it cost compared to using heat shields and parachutes?

Re:I've seen this before somewhere

[Moofie]

Parachutes are pretty cheap. Operating rockets four to eight times as heavy as they need to be is not cheap.

Re:I've seen this before somewhere

[Moofie]

Considering that we haven't even proven the viability of single stage to orbit (and I personally don't think it's a particularly economical idea in the first place), talking about single stage launches to other planet(oid)s is just silly.

So, you're not the only person who can't see the point.

Re:I've seen this before somewhere

[thesupraman]

And what makes you think that this will NOT use paracutes, with maybe a small amount of fuel to allow a softer 'soft' landing? after all, that fuel would save a LOT of structuer that would be required so the vehicle survived the just-paracure landing in a re-usable state..

It is quite possible to use a different approach for a 30 foot height control test and a full re-entry.... you say you are a rocket scientist?

Perhaps it's time for a few lateral-thinking courses.

Me. the EVIL one.

Re:I've seen this before somewhere

[Moofie]

What makes me think that? Because that's not what the DC-X did, and that's not the design I'm arguing against. I argue that a powered descent phase of any substantial length is going to be cost-prohibitive, and does not provide important benefits to a landing on a body with an atmosphere.

You might do with some reading comprehension courses.

Re:I've seen this before somewhere

[dreamchaser]

Unless you ultimately want an all purpose vehicle that can be used on any planet. I know, that's not the immediate or even the intermediate goal, but that's a good reason to design the technology. A cheap, easily deployed sub-orbital craft could be useful to future explorer's/colonists. Having one standard design 'off the shelf' makes it even cheaper in the long run.

Plus, it's soooo Flash Gordon! ;)

Re:I've seen this before somewhere

[Overzeetop]

No, clearly this won approval due to the cool factor, and dies due to the practicality & cost factor. The "Oooooh, shiny!" effect is not lost on parts of NASA management, and is the second most powerful motivator for congress. (The first most powerful motivator for congress is the "Ooooooh, green in my district" effect.)

I worked with several PIs (principal investigators - heads of projects) while at NASA, and the truth is ugly. If it doesn't shine up real nice at the dog-and-pony show, it won't get the desired funding.

Example: Very Long Baseline Interefeometry is very accurate for determining motions in the earths crust, but it uses large, boring antennas to record boring signals from far away stars. Comparison of received signals against known time standards can be used to determine relative motion in the sub cm level (iirc).

Laser Satellite Ranging is not as accurate, but uses a bright green (Nd:YAG) laser several inches in diameter to "hit" a 150cm diameter satellite target in low earth orbit, and read the return signal (sometimes measured in single digit photons) to get the time of flight. By knowing the orbit precisely (bettern than 5cm @ 6000km), a the motion of a terrestrial station can be tracked over time. Due to the fast motion of the satellite, the laser can be seen actively tracking the target, and if you have two stations co-located (usu. for calibration) you get two green death-ray looking things firing to a single point in the sky. Cool factor off the charts.

Can you guess which one got better funding? Lasers. Both worthy projects, both studying the same thing using different techniques. One with a much easier funding path.

Re:I've seen this before somewhere

[Moofie]

If I thought NASA had any serious plans to go to another planet, I'd be totally behind them.

The thing is, all the interesting planets have atmospheres. Yes, that does imply that the moon is not an interesting planet. Been there, done that, got the T-Shirt. Exploration means going to new places.

Re:I've seen this before somewhere

[Thag]

John Carmack's Armadillo Aerospace group have also been doing vertical takeoff/vertical landing (VTVL) work. Both they and the Japanese group are concentrating on going lots of unmanned testing of subscale vehicles, so they're getting lots of experience and data at a fairly low cost.

Though, the Black Armadillo X Prize vehicle will use parachute recovery. I think that was because A) it's simpler and B) they were concerned about whether or not they would have the VTVL working on the big rocket in time. Maybe John Carmack will comment if he reads this.

Jon Acheson

Re:CFD, for the curious

[pmz]

Others have pointed out that gasses are fluids. To further pop the gas-liquid-fluid misconception, aerodynamics students are first taught low-mach flows, where the dynamics of gasses and liquids are very similar. This is why it isn't uncommon to see water tunnels in aero labs.

Re:How would NASA handle this problem

[RedFive]

Once upon a time NASA thought this way too.

One of the early lifting body X-plane designs was tested by towing it behind a car like a glider...

Re:How would NASA handle this problem

[Anonymous Coward]

Rutan is gonna win this thing on December 17th.

If you knew anything about the industry, you'd know that Rutan
doesn't know his aerospace from his arse.

Re:How would NASA handle this problem

[raider_red]

If you knew anything about the industry, you'd know that Rutan doesn't know his aerospace from his arse.

That's why he's had one success after another, right?

Creative Ford Driving?

[confused one]

but doesn't Ford stand for "Found On Road Dead"? That doesn't bode well for the design...

Re:Creative Ford Driving?

[ak_hepcat]

I also heard it as:
Fix Or Repair Daily
Failed On Race Day
F'd Over, Rebuilt Dodge

Re:Creative Ford Driving?

[CharlieG]

Or (particularly during the era of the GT-40)

First On Race Day

Re:Creative Ford Driving?

[Cackmobile]

Found On Rubbish Dump
Farked On Race Day

Re:Creative Ford Driving?

[confused one]

I take offense (slightly) at the last one. Since my truck is an '84 Dodge FrankenTruck (built out of the parts from at least three other trucks and one car).

Then again, maybe you're right... = )

Re:CFD, for the curious

[iCat]

The definition breaks down in zero g, then?

Re:CFD, for the curious

[Animaether]

The 'somewhat misleading' was intended for the general usage of the term 'fluid'.

As in the same people that will say we 'breathe in oxygen', when the better part of the air we breathe tends to be nitrogen.

*tattoos on his forehead that this is a scientifically-inclined site*

Oh, come on.....

[Anonymous Coward]

Every one knows if you're going to do a suborbital drop of a vehicle it has to be '62 (if animated) or '57 (if in non-animated panels) corvette.

Note: http://www.imdb.com/title/tt0082509/

That's nothing...

[azav]

In the mid to late 80's I was part of CFD experiments where the pilot was loaded with thirteen screwdrivers and a parasail. The polit and parasail were pulled to launch pulled by a Ford F150 across the desert over the outskirts of Fresno (actually Sanger), Ca.

I think I could see my house from up there.

I love the japanese ship...

[gsdali]

They take off and land like the ships in old scifi and especially liek the ship in Tintin Destination Moon. image

Re:CFD, for the curious

[srvivn21]

Not so. You won't be able to "pour" said fluid in, but you can certainly pump it. It will still conform to the shape of the container.

Preventing fluid escape as you fill the container is an exercise left to the reader.

i like this guy...

[mantera]

Burt Rutan is such a great idol figure for any aspiring youth; he's cool as elvis, no nonsense as any good ol' american commonsenser, creative as da vinci and alternative as it can be yet deeply respected and admired by the "establishment" guys of his craft. The fact that he can make a design company as relatively small as his sustain itself and succeed in a market that is dominated by huge corporations that not only are deep pocketed and heavily staffed but also capable of yielding political influence, such as boing and lockhead martin, and just do his thing yet sell good without "selling out" is phenomenal and very inspiring. His design are truly creative and beautiful. It's a testament to a design when it's not only highly functional but also beautiful, and wild in a way that's unlike any before yet amazingly simple and makes sense in a way that makes you think there's no good reason why it shouldn't have been this way all along. He should a case study on the list of everyone who's even remotely interested in innovation.

NASCAR = IAMRAD

[Baldrson]

How about all those young studs who want to risk turning themselves into hamburger for speed and glory leaving NASCAR and going to form the International Association for Manned Rocket Aeronautical Dragsters; or IAMRAD.

Rather than a 1/4 mile horizontal drag race, make it ia 1 mile vertical drag race with total flight staying within the limits of Class E airspace, preferably below 14,500 ft.

Start with the Rocket Guy's 15,000 ft flight as a standard and do exhibitions involving dual launches of these vehicles. Grandstands must of course be at a safe distance but you don't need to be too close to something like this for the thrill of your life. There's a lot more energy being released in these drags than a typical 1/4 mile drag of course, and a lot higher likelihood of fatalities to the "drivers" but if you move it out to a remote area you can have some serious fun while developing the flight systems needed to carry men to orbit.

I like the X-Prize and all but really there needs to be some serious motor-head madness here with the motor babes and all.

A side benefit of this sort of competition is we get to find out if the spam in a can idea of manned rocketry is actually superior to human guidance. We all know someone will just have to attempt human guided rockets.

Re:How would NASA handle this problem

[Moofie]

Do you have any substantiation for your claim, or are you trolling?

And I DO know something about the industry.

Re:CFD, for the curious

[iCat]

A 1 litre volume of water released into a 10 litre volume container under zero g will form a sphere. It doesn't form a pool or a puddle.

CFD - now I get it!

[apsmith]

I'd seen the report on their resolving this problem a week or two ago (can't find the news item now though...) but had not noticed their creative use of the term CFD!

Re:CFD, for the curious

[mnemonic_]

Indeed... to add a bit though, fluid dynamics differ primarily from what's termed "gas dynamics" in compressibility. Whereas fluid dynamics deal with constant densities, gas dynamics involve compressible flow (supersonic flight, interiors of jet engines, etc.).

Re: Its easy to get into space heres how

[BrianMarshall]

You forgot the ablative coating.

Re:CFD, for the curious

[merdark]

It makes a tremendous amount of sense, mostly because it is super cheap.

Maybe, but you can't achieve very high speeds with this. Maybe you don't need to have such high speeds, but something about a suborbital flight suggests to me that high speeds are important.

Now the Avro company (who made the unfortunatlly scraped Avro Arrow), launched scaled down models on rockets. Of course, maybe this is harder to monitor than using a truck. On the other hand, you get much higher speeds and it is also super cheap.

Re:CFD, for the curious

[Moofie]

Depends on how you release it. If you can keep it from being disturbed by air currents, and you let it sit there for a REALLY long time, it will form a sphere.

Surface tension is a very not strong force. A litre of water masses what, a kilo? Surface tension force in water is (if I remember correctly) teeny fractions of a newton per unit length, which must be integrated over the surface, blah blah math happens now, but you don't have much F to do MA.

So, forming that sphere is not going to be easy.

Re:CFD, for the curious

[Moofie]

Since the pitch problem was occuring on landing, you may safely conclude that the speeds involved were not great. I wouldn't want to land a plane a whole heck of a lot faster than a powerful truck can travel.

Gosh, maybe this Rutan guy knows what the fuck he's doing, huh?

Re:CFD, for the curious

[Moofie]

Hmm. Both of the textbooks I have on the subject refer to "fluid" mechanics when they talk about both gas and liquids. One is a basic text, split pretty evenly between liquids and gases, and the other one is almost exclusively aerodynamics.

So you're wrong. Sorry.

more RVT

[savuporo]

The most comprehensive collection of info on ISAS RVT. There are links to videos of previous flight test campaigns. BTW, japanese heavy industrustry giant IHI ( best known as a turbomachinery manufacturer, yeah, thats superchargers for you ) has been contributing to this project. With Japanese industry giants involved, it might not be long before you can take to the skies with Toyota Spacecruiser.

Re:How would NASA handle this problem

[pmz]

If NASA had this problem they would have had to build a Wind Tunnel and finance the development of a Supercomputer, in the "correct" congressional district. Ensuring future funding of the program.

The F150 solution goes to show what the private sector can do, given the proper motivation.

Sadly, people are still going to vote for socialized healthcare in 2004. Great, my next doctor visit will be managed by a NASA clone.

Re:How would NASA handle this problem

[HenryWirz]

I think you may have your Rutans confused. We are talking about Burt the Engineer and successful entrepreneur, not Dick the test pilot. Burt designed the airplane that Dick flew around the world. Dick is not involved in the Xprize competition. He part of XCOR probably more as a figure head and test pilot.

Re:CFD, for the curious

[merdark]

Gosh, maybe this Rutan guy knows what the fuck he's doing, huh?

Do you *try* to sound snotty? Or is that just your natural charm? Did you see me say that Rutan was an idiot in my post? No. So quite being condecending.

Re:CFD, for the curious

[Moofie]

Sounds like somebody needs a hug.

Don't bother arguing

[DrMorpheus]

This is Slashdot, home of the sophmoric, hair-splitting, pedantic dilettantes.

Required King of the Hill reference

[DrMorpheus]

Naw, it's Fix It Again Tony...