# New form of propulsion

1. Sep 29, 2007

### Mackay1011

Hey, I know it's easier said then done but why are scientists spending so much money trying to improve the way we travel using "fuel" i.e hydrogen or whatever they use to go mach 2 plus. lets be realistic we are never going to be able to travel far into space because it uses to much fuel and we would run out.

Rockets are crap because they also dont last long. isnt there anything in space itself that we could use to propel "really fast" into space, then we wouldn't run out?

or, send a satelite thingy into space and try to land it on an asteriod and let the asteriod do the work?

please reply in detail, thanks

2. Sep 29, 2007

### D H

Staff Emeritus
We've sent people to the moon and unmanned probes a LOT further with existing rocket technology. That said, the world's space agencies do fund research into more advanced technologies.

BTW, Mach 2 is slow. Very, very slow. You have to get to Mach 25 just to get into low Earth orbit.

3. Sep 29, 2007

### Colin1

The Bussard Collector popularised by the Star Trek franchises is actually a factual, though at present theoretical propulsion system; it was given a tongue-in-cheek airing on the series way back in the 60s, which is when the theory was evolved if I recall. They were the red, glowy bits on the front of the warp nacelles.

I think the theory is that ionized EM fields around the engine, scoop hydrogen or some other stellar mass into the ramjet engine. Unfortunately, this stellar mass is only present in nanoscopic amounts per cubic metre of space, meaning the ionised scoops would need to trawl something like 10^18 m of space to collect a gram of anything 'burnable' - which could explain why it'll probably remain on the drawing board for some time yet.

4. Sep 29, 2007

### mgb_phys

But it does have the interesting feature that as you go faster it gets more efficent - so if you want to go to andromeda it's pretty handy!

5. Sep 29, 2007

### Danger

Mackay, I suspect that you are making a fundamental error regarding space travel. That's based upon your statement about the fuel running out. It isn't like an aeroplane or car on Earth that stops when it's out of gas. A space vehicle will continue on at the same velocity that it had after its last production of thrust. Realistically, a vehicle will retain sufficient fuel to alter that velocity if necessary, by either changing direction or changing speed.
Colin, the Bussard ramjet is indeed a workable technology, but complicated. Although it's been a few decades since I read anything about it, I seem to recall that it involves using a laser to ionize interplanetary or interstellar hydrogen, and then using a magnetic 'scoop' of several thousand kilometres in area to funnel it into a fusion engine. I'm a pretty serious Star Trek (all versions) fan, and I don't recall the mention of Bussard collectors before TNG. The warp engines were based upon matter/antimatter annihilation, not nuclear fusion. A Bussard ramjet could certainly suck in enough hydrogen, which would be pure protons in its ionized state, but it couldn't gather the antiprotons to react them with.

6. Sep 30, 2007

### Mackay1011

Danger you have explained pretty good :D thanks, so with the PROVEN technology that we have at the moment how fast could we travel in space and when the fuel runs out we could still maintain that speed.

A gas cylinder is compressed and when it blows up it shoots into the air....
cant you really cram loads and loads of the most explosive fuel know and then ignite it when were in space and stay at a constant speed of say 60,000mph? or something

7. Oct 1, 2007

### malawi_glenn

Scientits dont waste money. Politicians give money to scientists to do certain tasks.

8. Oct 1, 2007

### Janus

Staff Emeritus
That depends on how much fuel you have on hand. The more fuel your rocket holds, the faster its final speed will be.
The equation goes like this:
$$V_{final} = V_{exhaust} \ln (MR )$$

Where MR is the mass ratio, or the mass of the rocket plus its fuel divided by the mass of the rocket alone

The other factor is the exhaust velocity (how fast the gases shoot out the back of the rocket). The higher this velocity, the faster your rocket will end up going for the same amount of fuel. This is a measure of the efficiency of the rocket. The exhaust velocity is a function of the energy content of your fuel and how hot in burns.
In space, as long as the fuel is burning at its hottest, it doesn't really matter if we burn it up fast or slow, we still reach the same final velocity.

There is a limit as to how hgh an exhaust velocity you can achieve with chemical explosives, which is why research is being done in propulsion systems such as ION drives, which can achieve much higher exhaust velocities, and thus can reach higher speeds using less fuel.

Last edited: Oct 1, 2007
9. Oct 1, 2007

### quetzalcoatl9

the Bussard ramjet is fairly unfeasible as it stands since (a) the density of hydrogen in free space is estimated based upon an average determined within the solar system and (b) by far, nearly all of that scarce hydrogen will not be ions but rather will be in it's electronic ground state - one would be lucky to find a significant amount of free ions. as for somehow actively ionizing and then electrostatically collecting, good luck with that.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook