How to go about getting into Aerospace?

[Monkey]

[SOLVED] How to go about getting into Aerospace?

Hi, I'm a Computer Science student, but much of my interest is in Physics.

If I were to say... attempt building a space craft, what is the most efficient and most cost effective method of propulsion to use?

NASA is too slow :) I wan't to get into space before I die.

Monkey

 

[LURCH]

Hi Monkey,

NASA's Buerocracy may seem a bit stifling, but their systems are the best on the planet (for now). It's possible that one of these guys might top them soon. I'm betting the best way into space will be an air-breathing engine to take you to high altitude, then start injecting O₂ when the air gets too thin.

 

[Tyro]

Nuclear thermal engines are the way to go. The only disadvantage is that you don't want a Columbia or Challenger happening to you with a vehicle using nuclear thermal propulsion. Apart from that they generate the highest specific thrusts among other engine types (really a nuclear power vs. chemical power argument).

Nuclear thermal engines rely on using a propellant gas acting effectively as the 'coolant' for a nuclear reactor. Current designs would invariably use fission power, but the goal is to use the most abundant element in the universe...hydrogen...as a means of both propulsion and power.

 

[enigma]

Originally posted by Monkey

what is the most efficient and most cost effective method of propulsion to use?

Pick one or the other

The "best" depends on the mission, cost, and launch constraints.

 

[Monkey]

I think I'm going to use 90% H2O2 for fule.

 

[Tyro]

The thing about hydrogen peroxide as an oxidiser (it can't be used as a fuel!) is that you are lugging around dead weight water. Even if the ship was one big hydroponics ship you couldn't possibly use that much water with a half efficient scrubber system.

 

[Phobos]

Originally posted by Monkey
what is the most efficient and most cost effective method of propulsion to use?

Depends where you're going and how fast you want to get there. Rocket fuel will get you to the moon faster than ion propulsion, but ion propulsion will get you to the outer reaches of the solar system faster than rocket fuel.

Anti-matter is the most efficient fuel...but it's not cost effective (since we've yet to be able to built a fuel tank for it )

 

[meteor]

Between the real and theoretical rockets, the rocket with major specific impulse is the nuclear photonic rocket, with a specific impulse of 5*(10^6)s. It has an acceptable thrust too.
It contains a nuclear reactor at such high temperature that the photons that leave the reactor provide a great thrust to the rocket

 

[Tyro]

*Puts Aero Engineer cap on*

Sometimes, specific impulse is not the only criteria you use for judging what type of engine to go for. Specific impulse only gives you a measure of how efficiently you are using the weight of your propellant. Obviously any method which accelerates particles to near-light or light speed, e.g. a xenon ion propulsion drive or photon-based ones will have high specific impulses.

But are they adequate for sharp course changes or even launch? The answer is no, at least not for the forseeable future. Even though a chemical rocket is horrendously inefficient by these terms, it is still used for launch instead of a XIP drive, for example. A chemical rocket has about 1/10th the specific impulse of a XIP drive - but it is still the preferred launch method. The reason for this is because, at the moment, the absolute thrust of a XIP drive < chemical rocket and the total weight (not normalised against the propellant alone) of the XIP drive system > chemical rocket. The XIP drive requires the xenon propellant, a separate source of power, an ionising chamber and its equipment, acceleration chambers and its heavy coils, etc. A chemical rocket is just fuel + oxidiser, the tank, some pipes and a big nozzle at the end with a convergent-divergent nozzle optimised for hypersonic exhaust.

Of course systems like a XIP drive can be scaled up to provide the absolute thrust of a chemical rocket. But with current technology, doing so would probably increase the rocket weight to the point that you will need to increase the absolute thrust again. Scale it up again, and the required thrust moves higher.