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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."
Hmm, I guess "suborbital flight" has nothing to do with flying submarines then. Shame, that was such a great image in my head.
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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.
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?
goto http://rizzn.com
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.
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.
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
I love Mondays. On a Monday, anything is possible.
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.
And the brethren went away edified.
He means systems like interval arithmetic whereby you represent a Real number as an interval bounded by two machine floating point numbers.
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.
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I'd rather have a bottle in front of me than a frontal lobotomy
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.
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
I love Mondays. On a Monday, anything is possible.
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.
Seastead this.