Virgin space rocketship trials 'feather' re-entry system
Plummets toward Mojave with tail pointing straight up
The SpaceShipTwo suborbital rocketplane, commissioned by beardy biz-lord Richard Branson in order to offer zero-G exoatmospheric joyrides to wealthy customers, has flight-tested its unique "feathering" re-entry mode.
Engage shuttlecock mode, Mr Sulu
Virgin Galactic, Branson's nascent ballistic thrilljaunt venture, says that the test flight took place yesterday from the Mojave Air and Space Port in California. The SS2 rocket craft, dubbed VSS (Virgin Space Ship) Enterprise, was carried aloft by its jet-powered carrier aeroplane, VMS (Virgin Mother Ship) Eve.
On reaching an altitude of 51,500 feet, the rocketplane dropped away from the mothership and "feathered" its twin tails upward by 65 degrees. This is the configuration the VSSs are designed to use when re-entering the atmosphere at much greater heights in future.
Feathering is intended to offer a completely stable hands-off descent, requiring no fly-by-wire systems: the high drag generated by this "shuttlecock"-like flight regime combined with the craft's low weight is expected to mean only minimal heat generation during re-entry and thus allows the craft to dispense with thermal shielding or tiles. In operational service the ships will cease feathering and restore their tails to the normal horizontal position while still above 70,000 feet before gliding down to a runway landing.
In yesterday's test, however, the VSS plunged rapidly and "almost vertically" through nearly 20,000 feet in just over a minute before un-feathering at 33,500 feet. Test pilots Pete Siebold and Clint Nichols brought their ship in to a "smooth" landing at Mojave 11 minutes and 5 seconds after release from the mothership almost 10 miles up.
"The spaceship is a joy to fly and the feathered descent portion added a new, unusual but wonderful dynamic to the ride," said Siebold after the flight.
The SpaceShipTwos and their jet mothercraft are being built for Virgin by the famous company Scaled Composites, which made the Ansari X-Prize winning SpaceShipOne of 2004 and which has worked on various US military projects both known and – it's thought – unknown. The setup of Virgin Galactic was announced shortly after 2004's X-Prize triumph.
At the time Virgin expected to have its suborbital thrillride service running by 2007. Now four years past that deadline, the new suborbital birds have yet to fire up their tyre rubber and laughing-gas fuelled rockets: all flight tests so far have been unpowered glides.
The VSSs, once they go into service, will be spaceships of a sort in that they will briefly soar above the atmosphere: however some might quibble with the billing as they will be unable to actually deliver anything or anyone to any place off Earth. They cannot achieve orbit.
On the other hand, the project might be a stepping-stone to greater things, and in the meantime a $200,000 Virgin Galactic ticket is a hell of a lot cheaper than a proper space-tourist seat on a real orbital rocket (generally well north of $20m, if one is even available). ®
" the VSS plunged rapidly and "almost vertically" through nearly 20,000 feet in just over a minute before un-feathering at 33,500 feet"
I need a new pair of trousers just reading that, and I'm only on the first floor.
"3 miles a minute, vertically, you say? The first manned test, you say? Oh, I've got to take the goldfish to the vet that day, best get a temp in!"
Since the article doesn't actually answer your question....
Orbital velocity is very very fast indeed, and that speed is scrubbed of during reentry. The kinetic energy needs to go somewhere, and is converted to heat via friction.
SS2 and all other suborbital hops have no translational velocity, and the only KE they need to scrub is what they generate on the way down, vertical. Much less than that of orbital velocity PLUS the height, hence no (or minimal) heat shielding.
Or something like that.
Why so fast?
To complete the answer from the above excellent points. There is a fundamental difference between reaching the edge of space and going into a useful orbit. The energy required to get to the needed altitude it trivial. However the orbit that you are in has a rather unfortunate geometry. Whilst you will technically be in orbit about the centre of the earth's mass, the orbit's path also intersects the surface of the Earth remarkably close to the point where you took off. In order to get your orbit round enough that you get back to your starting point in space without embarrassing terrestrial intersections you need to put a heck of a lot of energy into circularising the orbit. Once you want to come back this same amount of energy has to be dissipated. Whilst you can get rid of some orbital energy slowly (aerobraking has been used for such things as orbital circularisation into Mars orbit from the much faster approach speed from Earth) you are going to find that there will always be a point where you are orbiting inside a thick enough layer of the atmosphere that you have no remaining choice about the rate at which the energy must be got rid off. The answer being: very very quickly.