Propulsion Systems Quotes

Flight by machines heavier than air is unpractical and insignificant, if not utterly impossible.

Chemical propulsion is obsolete to go anywhere other than the moon. Three days - that's acceptable. But for Mars, we need propulsion technologies to get us there in, say, 60 days - then spend whatever length of time we want to spend and return when we want to come home.

If we did not have such a thing as an airplane today, we would probably create something the size of N.A.S.A. to make one.

Rocket engines generally are simpler than jet engines, not more complicated.

If you think about the energy that a rocket engine has to put out and all the fuel and you're sitting on top of like a bomb. And on the Space Shuttle, that big orange tank is filled with liquid hydrogen and liquid oxygen, the white cell rocket boosters on the sides are filled with solid propellant. There's a lot of energy in all those chemicals there and you've got to control it in a way so it doesn't explode. So, there's a lot of plumbing, a lot of valving, a lot of control systems, and it's a very complicated thing. So, how do you bring the price of that down?

I don't know why I always liked aerospace engineering. I was in the 10th grade when I figured that's what I wanted to do.

Artificial flight may be defined as that form of aviation in which a man flies at will in any direction by means of an apparatus attached to his body, the use of which requires personal skill. Artificial flight by a single individual is the proper beginning for all species of artificial flight, as the necessary conditions can most easily be fulfilled when man flies individually.

I have had the feeling that a properly constructed flying-machine should be capable of being flown as a kite; and conversely, that a properly constructed kite should be capable of use as a flying-machine when driven by its own propellers.

Building and launching rockets has been a lifelong hobby that my son and I share. We regularly travel to Nevada's Black Rock Desert to launch rockets.

No data on air propellers was available, but we had always understood that it was not a difficult matter to secure an efficiency of 50% with marine propellers.

By the time I was 13, I was very interested in rocketry.

If it were possible - and I hope it will be some day - I'd like some sort of anti-gravity travel capsule: some way to travel around the without the need for jets and wings and so on.

Research into manned spaceflight is shifting from low-Earth orbit to destinations much further away, like Mars and the asteroid belt. But society will have to invent many new technologies before it can plausibly send people to those distances.

Whether solid rockets are more or less likely to fail than liquid-fuel rockets is debatable. More serious, though, is that when they do fail, it's usually violent and spectacular.

Trying to build a spaceship by making an aeroplane fly faster and higher is like trying to build an aeroplane by making locomotives faster and lighter - with a lot of effort, perhaps you could get something that more or less works, but it really isn't the right way to proceed.

The romantic appeal of solar sailing has ensured that its advocates consistently come from the worlds of both science fiction and science fact.

Really exotic methods of propulsion . . . will have to be devised to get there. How it will be done, I do not know. Whether it will be done, I am not quite certain. But I would bet it can be done.

Further ahead, I'd like to see tiny spacebots - smaller than your cell phone - travel outside our solar system to the nearest star system, Alpha Centauri. By keeping the mass of those spacebots low, we could more easily accelerate them.

Sometimes people wonder why aeroplanes are so cheap and rockets are so expensive. Even the most superficial comparison shows one obvious difference: aeroplane engines use outside air to burn their fuel, while rockets have to carry their own oxidisers along.

What can you conceive more silly and extravagant than to suppose a man racking his brains, and studying night and day how to fly?

Space architectures capable of supporting a permanent human presence on Mars are extraordinarily complex, with many different interdependent systems.

The rockets and the satellites, spaceships that we're creating now, we're pollinating the universe.

Designing aircraft and racing cars is an extremely exciting thing.

The wake doesn't drive the ship

We do need different types of propulsion to get to Mars. I wrote one of the first Ph.D. theses on that in the 1960s.