What’s the News: Virgin Galactic’s plans for taking tourists into space have inched closer to fulfillment: earlier this month, the company’s SpaceShipTwo successfully demonstrated the technique, called “feathering,” that will allow the ship to reenter Earth’s atmosphere. In this video, you can watch the ship, designed to behave like a badminton shuttlecock, tip and roll as the pilot flips the craft’s tail to a 65 degree angle, which will brake SpaceShipTwo while it’s still high in the atmosphere. This means the ship will descend slowly enough to keep from igniting as it reenters.
How the Heck:
- Velocity is the major reason objects burn up when they enter the Earth’s atmosphere—the friction between a speeding meteor and the gasses in the atmosphere, as well as the heat generated by the compression of the gasses as the object bores Earthwards, is so great that the meteor ignites .
- The Space Shuttle is covered with heat shields that absorb the heat generated by friction, but there are more elegant solutions for flights that don’t need to go into orbit, including feathering, which was first described in 1958. With this technique, part of the craft’s tail flips up to increase drag early in the process, so as it hurtles deeper into the atmosphere it doesn’t reach the velocities that result in ignition. A craft coming in from orbit would be going too fast to take advantage of feathering, but SpaceShipTwo is designed for lower, and slower, suborbital flight.
- Although this test didn’t involve leaving Earth’s atmosphere—it all took place within—it’s exciting to see that this design indeed works as expected. Since October 2010, SpaceShipTwo has undergone eight test flights, with four in the last month.
The Future Holds: Virgin Galactic has said that they’d like to start taking up customers—each of whom will pay $200,000 for a seat—as early as next year. But numerous other systems remain to be tested, and once Virgin Galactic has it working to their satisfaction, they’ll still need to seek government approval. We’ll see.
May 20th, 2011 at 4:24 pm
How is it new when it’s exactly what SpaceShipOne did in 2004?
May 20th, 2011 at 6:32 pm
I thought it was pressure that caused the heat of re-entry. Wouldn’t every part of, say, the Mercury craft have suffered friction, instead of just the underside, where the ablation shield was?
May 20th, 2011 at 7:02 pm
I thought it was the compression of the air that caused the heat, not friction.
May 20th, 2011 at 8:09 pm
branson is a fraudulent idea stealing arsehole, so called global earth challenge was just a way of stealing everyones knowledge for free. CUNT!!!!
May 20th, 2011 at 9:08 pm
Branson and team are great. It is so great to see some one and his team do things extraordinary. It’s like we are seeing the time of Howard Hughes, which most of us did not get to experience. Except this time it is Richard Branson, the man with the VISION that all of us can get behind. He is not someone who lets people say he can’t do it. He involves the brightest minds young and old and makes things happen. Simply great. If only I could also contribute to his team in some way, I would be inspired to do so.
May 21st, 2011 at 9:36 am
Adam, it is both. It’s the friction of gasses that causes the heat. Compression itself causes heat (just like released compressed gases will be cool), but in the case of atmosphere reentry it’s the friction of all the air being smashed into each other that causes the heat, more than just the heat effect of compressing gas.
May 21st, 2011 at 10:43 am
I remember an old episode of Skeptics Guide to the Universe that talked about friction/compression. I think it was “Science or Fiction” segment. Bob Novella said it was friction, but Steve Novella explained it as compression.
This is pretty neat. $200,000 is a bit much for my blood, but I can’t wait til it starts happening. Maybe the experience will inspire the affluent to give some money for space exploration.
May 21st, 2011 at 2:49 pm
$200,000 is a lot better than the millions it would cost you to catch a ride on a Soyuz flight. Granted, the latter is to orbit, but if you have the means, that $200K may be well worth it.
I hope it is for people far more well-heeled than myself, because if it is, then we may finally see scales of economy that would make space accessible — albeit briefly — for the likes of us, the hoi polloi of the middle class.
May 23rd, 2011 at 9:02 am
You all beat me to it. It’s compressive heating, not friction.
May 23rd, 2011 at 9:51 am
this is absolutely amazing stuff and breakthrough by virgin atlantic! Thumbs up to branson and his team!
May 23rd, 2011 at 11:35 am
Seeing that craft fold in half to slow it down was absolutely amazing. Think of the enormous pressures brought to bear on that machine during that phase. Simply amazing.
May 23rd, 2011 at 11:38 am
@Sion, Chris, Kin et al–yes, good catch, compression is a big part of re-entry heat. Text tweaked.
If you’re interested in this topic, there’s a long discussion over at Bad Astronomy from a while ago: http://blogs.discovermagazine.com/badastronomy/2010/02/22/pic-of-the-shuttle-reentry-from-space/
May 24th, 2011 at 10:26 am
Perhaps in more detail (IANAAEIRL*):
Objects moving at greater than the speed of sound in some media form a shock wave, where molecules slowed by hitting the object hit oncoming molecules moving at greater than the speed of sound. The shock causes compressive heating, and the shock is typically hotter than the object forming the shock. Heat transfer to the object increases with sharpness and curvature; thus the shuttle and re-entry capsules have very flat and rounded shapes.
The converse process may also be illustrative. If you push more and more air through a venturi, the air flow and speed increases with pressure — until the speed approaches the speed of sound. Then as pressure is further increased, a shock forms across the mouth of the venturi, and the air compresses (and heats), the speed through the venturi staying below the speed of sound.
This is a significant issue for jet engine design. Airflow in engines is necessarily subsonic; slowing the air down for an engine in a supersonic jet engine requires care: simple shocks compress and heat the air substantially, causing substantial energy loss through heating. The compression is good (jet engines’ efficiencies are dependent on “pressure ratio”, essentially equivalent to the compression ratio of an internal combustion engine), and may be used on its own, but usually needs to be done through oblique shocks rather than a single head-on shock to avoid excessive heating and energy loss. (Thus, e.g., the adjustable aero-spikes on the SR-71 whose shock is used to compress air entering the engines. At high speeds, these shocks do the bulk of compression for the engine. (Or is that the compression of bulk?))
(* I Am Not An Aeronautical Engineer In Real Life)
June 8th, 2011 at 5:25 pm
Everyone was so fascinated with the friction vs compression debate that no one noticed that Nick managed to slip in one of George Carlin’s “seven dirty words”. I am surprised that it has stayed up for almost 3 weeks.
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