Ion rocket engine powerfull enough for space flight?

[-Slacker-]

Was wondering if an ion rocket engine could be made powerful enough to lift a spacecraft in orbit, or even out of orbit (or at least LEO), provided it has an adequate (hypothetical) power source.

From what I know, ion engines are great for propelling a spacecraft that's already in space to very high speeds, because it can burn for years, but right now they are not even close to powerful enough for liftoff into space.

So would it be achievable with sufficiently advanced technology, like, say, miniature laser fusion power plants or whatever (dunno, I did say "hypothetical", the power source itself doesn't mater - more specifically, the means to generate enough electrical power for the actual ion engine)?

 

[SilthDraeth]

Will be watching this thread to see what the brains in here say.

 

[Lemon law]

My immediate small mind comment is why can't both technologies be used? A chemical rocket of great power to lift the the payload into into earth orbit. As the chemical rocket is then discarded as useless weight. And then, a far lighter and more efficient ion engine can be used to go the longer distances at slow but steady acceleration.

 

[-Slacker-]

I think this method is already being used.

The reason I'm asking is because it seems to me that, if the method is viable, it could have a lot more potential than chemical rockets, as the power sources and engines get progressively miniaturized. And I base that on the expertise that I just pulled out of my rear end ^_^ ... I realize I'm rambling here, but it would be cool to know if ion-engine space lifters are a possible feat.

 

[PlasmaBomb]

I think this method is already being used.

The reason I'm asking is because it seems to me that, if the method is viable, it could have a lot more potential than chemical rockets, as the power sources and engines get progressively miniaturized. And I base that on the expertise that I just pulled out of my rear end ^_^ ... I realize I'm rambling here, but it would be cool to know if ion-engine space lifters are a possible feat.

Ion engines are good at providing a small force for a long period of time. Like 1N over years... enough to accelerate in space because there is almost no opposing force, but orders of magnitude under the force that is needed to get into space in the first place.

http://en.wikipedia.org/wiki/Ion_thruster

 

[Revolution 11]

I am borrowing a comment on ArsTechnica's recent article on the Falcon heavy rocket by SpaceX.

"If you can find a way to get into orbit that's more cost efficient than lighting off hydrocarbons and oxygen in a metal bottle and shooting the hot gas out of the end, and doesn't a) irradiate half the continent (nuclear rockets) b) involve reactants that will leave the pad a smoking crater if anyone sneezes (look up ozone as a oxidizer) c) leave a vapor trail of vicious toxic residue (look up fluorine tripropellant) d) require materials made from unobtanium or e) require an complete rewrite of known physics, let us know."

http://arstechnica.com/science/2012/05/falcon-heavy-rocket-dream-chaser-vehicle-move-forward/

 

[AUGieDogie]

Interesting that the spaceX guy didn't talk about the shuttle. True the SRBs are toxic. But the Main engines run on water. Hydrogen and Oxygen.

Ion thrusters will probably never be strong enough to break orbit.

Project Orion Atomic propulsion
http://www.imdb.com/title/tt1039992/
If we could just get them off the ground (avoiding fallout) the damn things could make a fair percentage of light speed.

 

[irishScott]

Not as they are currently known.

An Ion Engine conceptually consists of a tube with two mesh grids through which propellent is injected. The first grid gives the propellent a positive charge, and the propellent particles are then attracted to the other grid which has a negative charge. This attraction and the motion it produces is what provides the thrust. It's efficient as hell, but not very significant by comparison to other techniques.

Barring some insane, super-light construction well beyond current tech, there's no way I know of (with my amateur space-nerd knowledge) that an ion engine could even overcome its own weight in the presence of Earth's surface gravity.

But you are right in the fact that it is inefficient power generation that is currently holding back manned space exploration. I seriously hope the hot fusion plant prototype they're building in Europe works, and that we can miniaturize it somehow.

 

[jagec]

But you are right in the fact that it is inefficient power generation that is currently holding back manned space exploration. I seriously hope the hot fusion plant prototype they're building in Europe works, and that we can miniaturize it somehow.

It doesn't even have to be efficient power generation. It just has to have a great power-to-weight ratio, not cost an absolute fortune, and work in space.

Basically we're where aviation was at the time of the Wright brothers. The technological limitations of the time made flight POSSIBLE, but very, very difficult.

 

[Revolution 11]

We already have 2 of the 3 criteria you mentioned. Current chemical propellants have great Thrust-Weight-Ratios (TWR) and work in space under conditions we understand well through decades of experience. Cost is the only factor holding us back and I think with private commercial spaceflight growing as it is, the cost will drop rapidly for low-earth orbit.

The only future tech I think would be viable from a risk point of view (environmental, hazard, cost, viability) is some sort of fusion power. This could change the cost equation but ion engines, fission power (way too risky and legal problems), and other technologies will not beat old-fashioned chemical rockets.

I am still hopeful for some sort of space elevator which would make space travel come down to the ease of international flight.

 

[Paratus]

Earth to orbit - not any time soon. LEO to the moon or Mars, sure. It may take you a while (weeks) to build up enough speed to leave earth orbit but you would leave it.

Google VASIMR

(For refernce at 200kw they get 5.7N of thrust with an exhaust speed of 50KM/s)

 

[exdeath]

We aren't getting anywhere with anything less than some sort of field propulsion.

Propellant ejecting Newtonian impulse rockets aren't ever going to cut it for anything outside our own solar system.

 

[exdeath]

It doesn't even have to be efficient power generation. It just has to have a great power-to-weight ratio, not cost an absolute fortune, and work in space.

Basically we're where aviation was at the time of the Wright brothers. The technological limitations of the time made flight POSSIBLE, but very, very difficult.

The Wright brothers didn't need a species changing breakthrough in physics.

 

[irishScott]

The Wright brothers didn't need a species changing breakthrough in physics.

And aside from interstellar travel, we don't really need one either. Even 10% the speed of light means we could reach pluto's orbit in days. Multiple planets worth of resources = enough time to figure out interstellar travel.

 

[wirednuts]

any news about them putting a spacecraft on a long magnetic rail that is positioned on the side of a mountain? using magnetic force, it would accelerate to astronomical speeds and simply sling the craft into space?

i think its possible, but they said the real challenge is to make a track long enough that there is enough time to accelerate slow enough that the g forces dont kill the passengers....

but for basic payloads, i think the space elevator really is going to happen. nasa sure thinks so!

 

[irishScott]

any news about them putting a spacecraft on a long magnetic rail that is positioned on the side of a mountain? using magnetic force, it would accelerate to astronomical speeds and simply sling the craft into space?

i think its possible, but they said the real challenge is to make a track long enough that there is enough time to accelerate slow enough that the g forces dont kill the passengers....

but for basic payloads, i think the space elevator really is going to happen. nasa sure thinks so!

Unfortunately I doubt the Space Elevator is going to happen anytime soon because of

1. The economy
and
2. It sounds stupid. Don't get me wrong I love the concept, but imagine going up to Joe Schmoe and saying "hey, you know what we should spend billions on? An elevator to space!" Sounds like something a 5 year old that just watched Star Trek would say right? Perception is everything.

 

[wirednuts]

2. It sounds stupid. Don't get me wrong I love the concept, but imagine going up to Joe Schmoe and saying "hey, you know what we should spend billions on? An elevator to space!" Sounds like something a 5 year old that just watched Star Trek would say right? Perception is everything.

i guess... but people were scared of microwaves when they first came out....

 

[-Slacker-]

I see.

So, from what I gather, the thrust on an ion engine doesn't scale with the amount of electric power you feed it.


Hmm ....


What about using obscene amounts of electricity to heat up fuel inside a container to scorching temperatures and ejecting it at very high speeds, pretty much like a chemical rocket, but without the need to carry shitloads of fuel because the low amount of fuel this conceptual vehicle would carry would be offset by the much higher temperatures/pressures inside the ignition container, and thus the thrust could be equal or even greater than that of a chemical rocket? (The advantage would be that such a vehicle could take off like a plane because it can adjust it's trust, or even turn the engine off at the pilot's discretion)

 

[slayernine]

Was wondering if an ion rocket engine could be made powerful enough to lift a spacecraft in orbit, or even out of orbit (or at least LEO), provided it has an adequate (hypothetical) power source.

From what I know, ion engines are great for propelling a spacecraft that's already in space to very high speeds, because it can burn for years, but right now they are not even close to powerful enough for liftoff into space.

So would it be achievable with sufficiently advanced technology, like, say, miniature laser fusion power plants or whatever (dunno, I did say "hypothetical", the power source itself doesn't mater - more specifically, the means to generate enough electrical power for the actual ion engine)?

My understanding is that the most efficient method to getting a ship into space is with a specialized launch vehicle and that ion engines are much better at slowly increasing speed over time which is excellent for space travel.

Escaping earth requires an immense amount of energy released in a short period of time which is best handled by big rockets. In space you need continuous thrust over a very long duration which is suited to an efficient low power engine that builds speed over time.

 

[slayernine]

Ion engines are good at providing a small force for a long period of time. Like 1N over years... enough to accelerate in space because there is almost no opposing force, but orders of magnitude under the force that is needed to get into space in the first place.

http://en.wikipedia.org/wiki/Ion_thruster

Exactly the reason why ion engines make no sense outside of space. It would be like blowing at a sail on a large schooner trying to get somewhere.

 

[jagec]

We already have 2 of the 3 criteria you mentioned. Current chemical propellants have great Thrust-Weight-Ratios (TWR) and work in space under conditions we understand well through decades of experience. Cost is the only factor holding us back and I think with private commercial spaceflight growing as it is, the cost will drop rapidly for low-earth orbit.

Current chemical propellants have awful thrust-to-weight ratios, just like the ones we used back in the 60s. We only use them because nothing else (currently) produces enough thrust to reach orbit.

Having to use the vast majority of your mass as fuel just to get into orbit is NOT a good thrust to weight ratio.

 

[exdeath]

Sigh... space is depressing. We are so weak and limited.

 

[richaron]

I read somewhere the idea is gaining more & more attention. But not simply by pissing ions off into space, but by using the fundamental property of said ions: charge.

Imagine positive ion beam from the launchpad against a positive vehicle (& perhaps a negative beam from a space station). Or what has captivated my imagination; some sort of cluster mechanics with a number of bodies & directable ion cannons, slingshoting one/some or even a sacrafice for momentum.

Edit: Since I didn't explicitly state it: it's heaps more efficient (but needs something to repell against)

 

[Revolution 11]

I read somewhere the idea is gaining more & more attention. But not simply by pissing ions off into space, but by using the fundamental property of said ions: charge.

Imagine positive ion beam from the launchpad against a positive vehicle (& perhaps a negative beam from a space station). Or what has captivated my imagination; some sort of cluster mechanics with a number of bodies & directable ion cannons, slingshoting one/some or even a sacrafice for momentum.

Edit: Since I didn't explicitly state it: it's heaps more efficient (but needs something to repell against)

Again, efficiency is great once you are in orbit but doesn't matter at all if you can't even launch off the ground as is the case with current ion engines. There must be sufficient thrust to get to orbit before you start worrying about thrust-to-weight ratios and other properties.

 

[Revolution 11]

What about using obscene amounts of electricity to heat up fuel inside a container to scorching temperatures and ejecting it at very high speeds, pretty much like a chemical rocket, but without the need to carry shitloads of fuel because the low amount of fuel this conceptual vehicle would carry would be offset by the much higher temperatures/pressures inside the ignition container, and thus the thrust could be equal or even greater than that of a chemical rocket? (The advantage would be that such a vehicle could take off like a plane because it can adjust it's trust, or even turn the engine off at the pilot's discretion)

How are you going to get that much electricity onto a ship without using massive batteries, unwielding solar panels (which will never provide enough power at Earth distances from the sun), or fusion/fission power?

The problem of weight remains (except for fusion which doesn't work yet).

Again, there is no current better way to get into LEO without using chemical rockets. I am still waiting for that space elevator though.....