What are billionaires waiting their turn to fly on a suborbital tourist trip looking for? For some, satisfying a childlike illusion that perhaps borders on obsession. For others it is a question of ego. But they all share a dream: “To boldly go where no one has ever gone”, as it was said in the introduction to each chapter of Star trek. Jeff Bezos’ space company has posted on his YouTube channel the full recording of the flight that made his capsule with a baptized mannequin Skywalker as sole crew member. The entire trip lasts 11 minutes. It’s worth a look to get an idea of what the first four Blue Origin passengers are going to see.
But where does space begin? The generally accepted boundary is the Karman line, a hundred kilometers above the ground. Whoever exceeds that limit, even for a few minutes, has the right to be called an astronaut. That is surely the main motivation of space tourists.
Although the border has not always been there. For many years, the US Air Force set it a little lower: Fifty miles (about 80 kilometers). That allowed several pilots of the X-15 (an experimental aircraft-rocket hybrid) to claim that title. Neil Armstrong, who flew the X-15 seven times, never exceeded that limit; he would have to wait for his incorporation to NASA to get over it.
The 100 kilometer level – more kilometer, less kilometer – is not arbitrary. It is the height at which the air is so thin that a conventional airplane would have to fly at enormous speed for its wings to develop enough lift to keep it in flight. Almost eight kilometers per second, that is, orbital speed: 24 Mach.
No aircraft reaches that speed. The spy plane SR-71 Blackbird it established its mark in something more than 3,500 km / h or, around one kilometer per second; and the X-15 more than doubled (equivalent to Mach 6′7). Both have been retired from service for many years.
But these are only theoretical considerations that are meaningless in practice. Following the curvature of the Earth at almost eight kilometers per second, the mere centrifugal force compensates for the weight of the spacecraft, so that it stays in flight without the need for wings: It is an artificial satellite.
Of course, at such speeds and only 100 kilometers high, the friction of the air, however tenuous it may be, makes it impossible to maintain orbit. The braking effect is so intense that the surface of the capsule becomes incandescent and – if not adequately protected – is destroyed in a few moments.
The flights that Blue Origin advertises are simple vertical jumps, almost like going up and down in a very high elevator.
A satellite rarely flies below 180 kilometers in height and even that level is very critical. The world record is held by Tsubame, a small Japanese vehicle that lasted a week going down to less than 168 kilometers to take high-resolution photographs. Some military satellites also occasionally descend to these levels, but it is a momentary maneuver to observe very specific targets and then rise again to safer heights.
All these factors explain why the flights announced by Blue Origin are simple vertical jumps, almost like going up and down in a very high elevator. The speeds that are achieved are relatively modest. There is no re-entry maneuver, which is always the most dangerous part of the mission, and no accelerations above a brief three “ges”; simply a fall from a height of 100 kilometers, stopped at the last moment by parachutes.
Rafael Clemente He is an industrial engineer and was the founder and first director of the Barcelona Science Museum (now CosmoCaixa). He is the author of A Small Step For [un] man (Dome Books).