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Thursday 5 May 2011

Hyperbolic Orbit

On 5 May 1961, as the result of a short trip on the end of a rocket, Alan Shepard became an instant celebrity and one of the greatest American heroes of the twentieth century. But was he really the first American in space? Personally I think it's an exaggeration to claim this... a Myth-conception created by a mixture of Cold War politics and the media's ignorance of science. If you're going to talk about space travel, you need at least a basic understanding of Newton's Law of Gravitation.

Shepard's trajectory in May 1961 was parabolic, the same as a ball thrown into the air, or any other object which is launched upwards with less than orbital velocity Vo. To enter Earth orbit (as Yuri Gagarin's Vostok spacecraft did three weeks before Shepard's flight), the trajectory must be an ellipse, which requires the speed to be somewhere between Vo and escape velocity VE = 2Vo. If the speed is greater than VE the object will escape the Earth altogether on a hyperbolic orbit.

The adjective "hyperbolic" can also mean "of exaggerated importance" (from the noun hyperbole, normally shortened to hype). In this sense, Alan Shepard's flight was hyperbolic as well as parabolic!

I don't mean to belittle Shepard personally -- after all, he was just doing a job, and had no control over how that job was presented to the world by NASA or the news media. Arguably, his flight required far more courage than Gagarin's had, since the latter had the benefit of a well-designed, well-engineered spacecraft that virtually flew itself, and was always well within its operational envelope. Soviet cosmonauts were never bothered by Shepard's oft-quoted worry that "every component was built by the lowest bidder"!

The Redstone rocket used for Shepard's mission (and Gus Grissom's similar flight a couple of months later) was designed in the early 1950s as a short-range ballistic missile, and was (in engineering terms if not in visual appearance) only a slight modification on the German V-2 rocket of World War 2. Test flights of captured V-2s in the late 1940s achieved similar altitudes to Shepard's flight, yet no-one at the time described them as "flights into space". Some of these flights even carried monkeys and other animals as passengers, with no great media fanfare. Under normal circumstances, I'm sure that Alan Shepard's mission would have been seen as "just another test flight"... if it hadn't been for the exigencies of Cold War politics, which demanded an instant U.S. response to Gagarin's flight into space!

Eventually, in February 1962, an American did make it into orbit: John Glenn, boosted into space by an Atlas rocket which was far more powerful than the Redstone. As a space-obsessed but scientifically ignorant schoolboy in the 1960s (from which period the postcard above dates), Alan Shepard was one of my great heroes, and I could never understand why grown-ups made such a fuss about John Glenn... after all, he was only the third American in space, wasn't he? And if the Americans really believed that Alan Shepard's flight was on a par with Gagarin's, they wouldn't have made a fuss about John Glenn either!


PoissonPete said...

Nevertheless, he did go into space (under any of the various definitions of the height it starts).

Related trivia question (I used this as a pub jackpot question once): what was the first animal sent into space?

Andrew May said...

According to "legal" or whatever definitions of space, you're right of course. The point I was making was that really spaceflight should be defined in terms of dynamics and not altitude -- i.e. if you fall back to Earth it's not really spaceflight!

On the animal question -- you've asked me that before, and I probably got it wrong. There is a Wikipedia article on the subject!

PoissonPete said...

There's a Wikipedia article on everything! But if you can think of something, I'll add it. Hold on, though - I don't think there's an article on "Subjects on which Wikipedia has no Article" ...

The trivia answer, for anyone who hasn't looked it up, is: a fruit fly.

Anonymous said...

Sorry for a tardy reply but I have only just discovered your blog, which is very interesting.

Even as a youngster back in the UK of the 1960s I used to be annoyed by the cold war politics of the space race. To me it was a pollution of the greatest adventure undertaken by humanity. One was led to expect mendacity and exaggeration from the Soviet monolith but it irritated me then — and it irritates me now — that western history paid — and pays — so little respect to the genuine achievements of the USSR’s space programme. After all, and despite the end result of the cold war, the Russians (and now the Chinese) are the ones still flying! The basic Russian design was so good that they can still use an adaption of it fifty years after it first flew. And they didn’t engage the services of a reconstructed Nazi to do what they did. That doesn’t mean that I denigrate the intelligence, diligence, fortitude and courage of the US programme participants: they rightly won the trophy and they deserve the credit for all that they achieved. But I do regret the less heroic political background and that so little attention is apparently paid to their similarly courageous and ingenious rivals.

< Soviet cosmonauts were never bothered by Shepard’s oft-quoted worry that “every component was built by the lowest bidder” >

That was a notion that returned to haunt the Americans a number of times, but the Soviets were often bothered by their own problems. Not only did cosmonaut Vladimir Komarov die in the progress of his flight, he knew that it was a likely outcome due to the endless technical problems in preparation for the mission in combination with political pressure from the Politburo to fly as quickly as possible. The mission was simply not ready and Komarov flew only because his good friend, Yuri Gagarin, was on the sub’s bench and would have been the one likely to die if he had declined.

Andrew May said...

Thanks veey much for your comments. I hadn't heard the anecdote about Komarov and Gagarin before -- ironically, of course, Gagarin was killed in a fairly mundane air crash less than a year after Komarov.