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What makes Virgin Galactic’s SpaceShipTwo more than just a high-flying plane?

The views expressed are those of the author and are not necessarily those of Scientific American.

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SpaceShipTwo (SS2) in the hangarWith all the hubbub surrounding the Monday unveiling of Richard Branson’s new SpaceShipTwo, billed by Virgin Galactic as "the world’s first manned commercial spaceship," some of us began to wonder: What makes a spaceship a spaceship? After all, the flights that Virgin Galactic is hawking for $200,000 do not put passengers into orbit. And as for one of the purported thrills of space tourism, weightlessness, that experience is attainable at or below altitudes reached in a typical commercial airline flight—in NASA’s "vomit comets," for instance.

So when is a traveler a space tourist and not just an airline passenger with a slightly better view and a much lighter wallet? Slate tackled the question back in 2004, when SpaceShipOne cracked the "official" space barrier in the course of winning the $10-million Ansari X PRIZE. That barrier, sometimes known as the Kármán line after Hungarian–American engineer Theodore von Kármán, lies at 100 kilometers above Earth.

According to the World Air Sports Federation, a governing body that keeps world records for flight, the Kármán line is the boundary separating astronautical flight from aeronautical flight. Although the federation’s secretary general told Slate that the choice of 100 kilometers was "fairly arbitrary," it is rooted in science. Von Kármán and his colleagues calculated that somewhere around that altitude, the atmosphere thins out so much that aeronautical vehicles would need to sustain essentially orbital velocities to generate lift. Rather than trying to ascribe a precise location above Earth where this transition took place, the federation adopted the round-number approximation.

So SpaceShipTwo, which is expected to rocket to about 110 kilometers, should indeed breach a barrier in both the terminology and the physics of flight. But that does not mean that suborbital flights such as those sold by Virgin Galactic have always basked in the same heroic glow as orbital shots. When the U.S. sent its first astronaut into space (that is, past the Kármán line), lofting Alan Shepard 187 kilometers into the sky in 1961, Soviet premier Nikita Khrushchev reportedly scoffed that Shepard’s 15-minute flight was a mere "flea hop." After all, the U.S.S.R.’s Yuri Gagarin had already orbited the planet.

Tom Wolfe, author of The Right Stuff, echoed that sentiment in a July op-ed for the New York Times, published as the 40th anniversary of Apollo 11 drew near. Recounting the U.S.’s initial lag behind the Soviets in human spaceflight capability, Wolfe denigrated (seemingly only half-seriously) Shepard’s flight and that of his successor Gus Grissom as "two miserable little mortar lobs."

So perhaps Virgin Galactic passengers won’t find their names enshrined in the Astronaut Hall of Fame. But at least, we imagine, they’ll get to skip the indignity of the TSA checkpoint.

SpaceShipTwo (center) attached to its mother ship Eve: Virgin Galactic/Ned RocknRoll

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  1. 1. cleudo2009 6:42 pm 12/7/2009

    Space flight 70 miles up? Contrast this to the ISS which has a *minimum* altitude of 280 miles.

    Briefly crossing the Karman line may bestow legitimacy to the enterprise, but is it really spaceflight and will the wealthy passengers feel they’ve had a worthwhile trip?

    I think not…

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  2. 2. acerbiter 7:43 pm 12/7/2009

    The altitude of the ISS is somewhat of a compromise between the highest orbit a space shuttle can reach and the altitude at which atmospheric drag would require too many burns (and fuel) to keep the station in orbit.

    Even at 340-360km (211-224 miles) [i.e not 280!] the station’s orbit is slowly declining due to atmosphere, and requires somewhat regular orbital maneuvers to increase the altitude (

    But maybe a few of those wealthy first passengers will change their view of the world, seeing it from (even 110km)’s gotta the "experience of lifetime"!

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  3. 3. fyngyrz 2:22 am 12/8/2009

    Personally — and I’m not trying to be prurient here, just honest — I’d pay for two seats in in that range for a trip where I got to lounge around long enough to get over whatever bad effects our bodies handed us over weightlessness (and there are quite a range of possibles there), and then have at least one long, luxurious and very experimental lovemaking session with my companion. For what amounts to a *very* short trip to where the atmosphere is thin… no. Speaking as a tourist, I know exactly what my priorities are. I can get short term, inexpensive zero G off a diving board or a cliff or by parachute jumping out of an aircraft. Plus the fun of the wind whipping past my face.

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  4. 4. martingowar 1:51 pm 12/8/2009

    Sounds like sour grapes by a few of the posters here….
    Personally I’d give my left arm for the opportunity of seeing this planet of ours from 70 miles up – even if it were for only a few minutes !

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  5. 5. Viadd 5:10 pm 12/8/2009

    Don’t count on skipping the TSA checkpoint. Passengers on the <a href="">commercial Vomit Comet</a> have to go through the TSA security theater, and screening space passengers is just as reasonable.

    Link to this
  6. 6. jgrosay 5:03 pm 12/9/2009

    Wie ein floh, aber oho!

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  7. 7. Quinn the Eskimo 10:42 pm 12/9/2009

    Richard Branson.

    Stay home, save big $$$$.

    Virgin in Space–false advertising.

    Link to this
  8. 8. Michael Hanlon 10:14 pm 01/3/2010

    I have thought of a practical application for the venture you are undertaking. Mr. Branson, if you have anyone following this blog, the copy below should incite interest. It is taken from George Musser’s blog article here about the third report of the planetary guys gathering in Puerto Rico earlier this year. Searching here with an engine input of ‘planetary bobmardment’ will get you there. I bring it to your attention because I did mention your operation in it. The idea::
    Here’s an intermidiate step for the <xox> scheme to function more within the range of human endurance.
    Place a Magnetic Rail Launcher in orbit, both around the Earth and around the Moon.Use chemical boost to reach the altitudes of the ‘guns’. Use Solar to power the Rails. Use the rails to boost payloads up to the velocity of the passing rock. From the shallowness of an orbital level gravity well, the amount of acceleration to go from rail orbital speed up to rock orbital speed should be low. An added benefit is that the rails can also be used as ‘Catchers’ to intercept a rock separated payload at both ends. Just reverse the current flow direction and pulse sequencing and the rail acts as a ‘Stopper’ too. (sorry jack.123, at this stage no rails needed on the rock (but maybe later perhaps)).
    So, now the cost of getting to the moon, once the infrastructure is in place is just about what Branson is using for Virgin Galactic. Next to nothing versus what NASA charges.

    Link to this

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