Bush Cancels trip to Pluto.

[Roman]

Originally posted by faded glory
Ion propulsion is a joke.

Why write it off just like that. For far away missions it is very beneficial as over long periods of time it enables space probes to attain high speeds without using ridiculous quantities of propellant. Hence it makes space missions much cheaper.

Controlled Atomic reactions is the way to go. Get to mars in 3 weeks. As opposed to 8 months with a normal chemical booster. NASA was designing the ship...the greenies did like it tho cause the word 'nuclear' was written all over it

But imagine being able to reach mars in 3 weeks. Saturn in 9 months... and beyond. It had alot of potenetial using controlled Atomic reaction bursts to get it moving.

But the greens worrys are justified. But there was a plan to assemble the ship in space and keep it above the earths atmosphere so there would be no danger.....

Well, as far as I am aware, there are two basic principles behind nuclear powered spacecraft. One actually uses nuclear to provide electricity for guess what - ion engines. That enables missions to places where solar panels are no longer useful.

The other way to power a spacecraft nucleary is to make the reactor heat up the fuel and then let it expand out through the nozzle, thus providing thrust. AFAIK this is more fuel efficient than chemical engines, but provides somewhat less thrust. It does provide very significantly more thrust than ion engine, but is less fuel efficient.

As you can see there is no easy solution. Different propulsion methods fit different objectives and missions.

BTW: I agree that the green rejection of nuclear power (both on spacecraft and on Earth) needs to be reevalued. Alternative energies are not reliable enough to ween us off fossil fuels on theur own.

[Roman]

Originally posted by aaglo
Construction&Civil engineer (no, not CIV-engineer )

I was considering aerospace engineering, but I have been persuaded to study economics and international relations instead.

[Dauphin]

Controlled Atomic reactions is the way to go.

I think laser pushed sails are the way to go. Ultimately they are by far the most efficient in terms of energy usage. If set up properly.

[faded glory]

Originally posted by Roman


Why write it off just like that. For far away missions it is very beneficial as over long periods of time it enables space probes to attain high speeds without using ridiculous quantities of propellant. Hence it makes space missions much cheaper.



Well, as far as I am aware, there are two basic principles behind nuclear powered spacecraft. One actually uses nuclear to provide electricity for guess what - ion engines. That enables missions to places where solar panels are no longer useful.

The other way to power a spacecraft nucleary is to make the reactor heat up the fuel and then let it expand out through the nozzle, thus providing thrust. AFAIK this is more fuel efficient than chemical engines, but provides somewhat less thrust. It does provide very significantly more thrust than ion engine, but is less fuel efficient.

As you can see there is no easy solution. Different propulsion methods fit different objectives and missions.

BTW: I agree that the green rejection of nuclear power (both on spacecraft and on Earth) needs to be reevalued. Alternative energies are not reliable enough to ween us off fossil fuels on theur own.

Concerning Nuclear Power Roman. No the idea behind the Nuclear engines had nothing to do with Ion. IT would have been a controlled and funneled nuclear reaction for propulsion. No Hiroshima or anything...a small reaction in bursts.

[Roman]

Originally posted by faded glory
Concerning Nuclear Power Roman. No the idea behind the Nuclear engines had nothing to do with Ion. IT would have been a controlled and funneled nuclear reaction for propulsion. No Hiroshima or anything...a small reaction in bursts.

Well as I pointed out there were two ideas about nuclear propulsion. One was essentially ion propulsion with using nuclear o produce electricity and the other involved a chemical propelant being heated by a nuclear reactor and then funneled through the nozzle to provide thrust. I guess you are talking about the second one.

I have never heard any suggestion about actually expelling the nuclear material itself to provide thrust. I think I am misunderstanding what you are writing - please clarify.

[Roman]

Originally posted by Big Crunch

Controlled Atomic reactions is the way to go.

Ultimately they are by far the most efficient in terms of energy usage. If set up properly.

Difficult to argue with that, considering they don't use any energy of their own.

[Dauphin]

Originally posted by Roman


Difficult to argue with that, considering they don't use any energy of their own.

Well you need to charge the laser.

The point moreover is that all the energy used is put into the kinetic energy of the satellite. With chemical rocket propulsion almost all of the energy created is wasted on the ejectile.

I have never heard any suggestion about actually expelling the nuclear material itself to provide thrust.

Similar

How do you funnel a nuclear reaction! Even a mini one.

[Roman]

Originally posted by Big Crunch
Well you need to charge the laser.

I assumed you were talking about the idea to tap solar wind. I am not sure just how workable it is, but if it did work no further energy input would be required. The laser idea is probably more practical, though.

The point moreover is that all the energy used is put into the kinetic energy of the satellite.

Is all energy converted into kinetic? I did not realise that, but than again I am not an expert on the subject. I thought the light, or whatever the laser emits is reflected back by the 'reflective sail'. However, since the light still exists it contains much of its energy, so only a tiny fraction of the energy is converted into the kinetic energy of the spacecraft. IIRC you are a physicist, so I would be grateful if you explained it to me (I don't mind equations, but do not make them too mind boggling).

[TCO]

I have actually heard of designs that use the direct impulse from nuclear explosions.

[Roman]

Originally posted by GP
I have actually heard of designs that use the direct impulse from nuclear explosions.

How????

[TCO]

I don't know all the details, but I think they have a plate at the back of the ship and they explode the bombs against the plate. Not sure of all the construction, megatonnage, and geometric details. I think the design is theoretical. Untested.

[Roman]

Big Crunch - please!!!

[faded glory]

Roman Nuclear reactions dont have to be that big. They can be downsized...diverted.....mixed and funnelled. Ill try and grab a link about NASA's program in the 70's concerning nuclear propulsion.

I think the biggest issues

1) How to shield the crew from radiation
2)How to keep somthing from going wrong and it falling back to earth.
3) How to get good PR considering the program was at its peak in the late 70's. (died right after 3 mile island ironically )

[aaglo]

You can find information abou fusion propelled spacecrafts from here. But I suggest that you don't believe everything you read from the internet.

Besides, it seems that fusion propulsion (FP from now on) is still science fiction (NASA estimates that the development of FP will take some 25 years)

[KrazyHorse]

Originally posted by Big Crunch

As to the speed the engine can reach - this is very misleading. In theory, every engine can attain any possible speed, but needs varying amounts of fuel to do so

Using single stage engines the amount of fuel required to increase its speed by x kms^-1 increases exponentially.

It one of the reasons that launch rockets are multi-staged, a single stage rocket can not reach orbit.

This is false. The logarithmic increase of deltaV for linear increase of fuel is not a flaw in single-stage designs; it is a flaw in using a reaction engine which must carry its entire supply of propellants on board (to wit, any rocket). Multiple stages simply aid a rocket approach this theoretical limit more closely. The reason an ion rocket has a higher practical top speed is that its propellants are ejected at a much higher velocity than those from a typical chemical rocket. It thus gains more thrust/unit mass of propellant, resizing the logarithmic curve dramatically in our favour. In fact, the terminal velocity of two identical rockets, one with chemical propellants which have Effective Jet Velocity (EJV-the speed at which burned fuel exits the rocket) of X m/s and one with ion propellants with EJV of Y m/s are simply related by the ratio Y/X. Given that ion drives (being much higher "temperature") have an EJV orders of magnitude higher than chem rockets, you can see that the implications are astounding. Admittedly these ion drives have a low rate of mass expulsion and have a correspondingly low thrust, but you can accelerate for years on a fuel supply which would be exausted in minutes by a chem rocket.