Yesterday was the 50th anniversary of Yuri Gagarin's groundbreaking space flight. What's odd is comparing the fifty years since his flight with the fifty before.
The fifty years from 1911 to 1961 saw manned flight go from not much more advanced than the Wright Brothers to a man orbiting the Earth. The fifty since - with a short detour in the first decade that had man go to the moon - have seen essentially no advance at all. We've gone from man orbiting the planet to man orbiting the planet.
Manned flight was a lot easier to address than spaceflight. People have been shooting rockets high into the air for a long time. Robert Goddard's early experiments led to Werner von Braun's V-2 twenty years before Gagarin. Getting to actual orbit was way harder.
The problem is Delta Vee. What goes up must come down, and that applies to V-2 rockets as much as a long fly ball. Orbit is different; the rocket not only needs altitude (relatively easy), it needs enormous horizontal velocity. The orbiting rocket is falling just like a WWII V-2; the high horizontal velocity is what keeps it from hitting the earth. Basically, as it falls, it moves horizontal to reach a point that is the same altitude over the ground.
The change in the horizontal velocity (the delta in the Vee, or velocity) is enormous for orbital flight. That's what's holding things back. Sir Isaac Newton will not be denied, and so rockets take a brute force approach, throwing away 95% of their launch mass - burning it to make the thrust to generate the Delta Vee that will place the payload in orbit.
While rocketry is simpler than air flight (from an engineering point of view), it's enormously hungry for energy. "Commercial space flight" will remain a tourist attraction - limited to taking people up really, really, really high - until someone figures out a way to generate the Delta Vee needed to put something into orbit without having to haul your Liquid Hydrogen and Liquid Oxygen up to 90,000 feet before you burn it.
Engineering is a cruel master, in that you can't cheat your way out of reality. After fifty years, someone needs to think differently - maybe a space elevator, maybe a linear accelerator on a mountain top that launches payloads at mach 12, maybe something else. Otherwise, another fifty years will go by without any progress.
9 comments:
Although, really, a rocket is based more on delta m more than delta v: the acceleration is produced by decreasing the mass.
Feel free to argue to the contrary.
We've gained a little more in the last 50 years of flight than one might realize. Gagarin's mission was slightly under 2 hours; nowadays we've had people in orbit continuously for years. The "getting there" part may have stalled, but the "staying there" part is still advancing.
If you want to see a weird but oddly compelling idea for a space elevator, go read the Wikipedia article on the space fountain.
@Czar, Even without decreasing mass you need enough thrust to accelerate from zero velocity. Granted, the decreasing mass reduces the requirement for Yet More Fuel.
That said, I don't have a good feel for the breakdown of acceleration due to (constant thrust and decreasing mass) vs. acceleration due to (big ass thrust) With multi-stage rockets I expect this has some interesting step functions.
Everything you ever wanted to know about delta-V (unless you actually want to build rockets) is at Atomic Rockets:
http://www.projectrho.com/rocket/
The site was created to give people writing hard science ficiton some hard science about spaceflight - including the necessary delta-V capability for a spacecraft in various missions. It includes some proposed alternatives like space elevators, space fountains, ground-based laser propulsion, magnetic linear accelerators, and others.
It's a good place to waste an afternoon or three if you're into that sort of thing.
As you've noted before, the biggest gains are in the early years of development. An unfortunate truth that is as implacable as Newton.
Hopefully someday soon there will be a breakthrough that will introduce a disruptive technology into the space business.
Well, the fastest way to increase ▲ V is to increase efflux velocity.
Freiherr Von Braun's colleague Hermann Oberst pointed out the method nearly 80 years ago. The thumbnail is Von Braun tried to get funding. No dice. Tried again at NASA. De Nada.
Sometime, someone will stumble over the history, and since we now have adequate power supplies make Oberst's method work.
Stranger
Newton's a tough taskmaster, for sure, but Maxwell is a motherf***er. Just try to make an electrically short highly efficient antenna. Here's a hint: there's about a Godzillion dollars at the end of that trail and people have been trying it for about a hundred years. No one has cracked that nut, yet.
But all laws of physics are like that. The car commercials are wrong. No one can break the laws of physics.
THere is a growing body of evidence, and it is compelling evidence, too, that Yuri Gagarin was not the first man in space. In fact, there is suspicion that one man and one woman went into orbit before he did, acheiving the distinction of being the first man, then the first woman, in space.
They unfortunately did not survive, with the theory being that the woman burned up on re-entry and the man fell to his death when his chute failed to deploy.
The Soviet space program was just a big kabuki show - no real substance or effort to safety at all.
The woman's death as I recall can actually be listened to as two italian brothers managed to instercept her transmissions on a ham radio back in the day (garnering much attention from the Soviets in the process.)
I don't know whether this is all real or not, but it sure is interesting!
Excuse me, I forgot to make the point that the reason that we don't know about these is because the Soviets covered them up to avoid embarrassment.
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