Diferences between electric engines

There seems to be a difference between several types or kinds of electric engines.

What is this difference?

As far as I know from literature they all are using the impulse of ions. There are ion engines, nuclear-electric engines and more - but they all seem to use ions. Is there an error in this and what is the error? If some elctric engines don't use ions which way do they drive a vehicle then?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Ion engine usually means something much more narrow than ions being involved in propulsion. Some quick google finds covering electric rocket propulsion concepts to some degree.

http://www.waynesthisandthat.com/ep2.htm
http://en.wikipedia.org/wiki/Spacecraft_propulsion
Note schemes like the resitojet which is electrical but does not even see use of ions.

Of significant importance are electrode-less schemes like VASIMR (Variable Specific Impulse Magnetoplasma Rocket) which should allow higher thrust/weight at similar ISP to conventional ion engines as well as other advantages.

Hello, nihialdrem,

that's a very important information for me.

I have to read the links but what you say seems to mean that I have understood the term "ion engine" wrong. I interpreted the term to involve a classification by kind of propellant. One kind of prpellant are chemicals, a second kind of propellant are ions accelearted by an engine, athird kind of propellant is light... and so on.

If it turns out to be right what I've said then this would mean that we were misunderstanding each other in the thread regarding the brilliant idea for reentry. What's relevant for me regarding JP Aerospace's engine is that it doesn't use chemiclas and so doesn't require huge tanks and stages and that it uses an engine which can provide impulse permanently during very long periods compared to chemical "engines".

The technical differences between several kinds of engines are details for me on a level below the vehicle because the vehicle consists of several components the engine is one of only. So for reasons which have to do with what I said in the thread "Synopsis Technology". This is so because the entrepreneural idea behind JP Aerospace's activities is the vehcile. From there it goes top-down into the details - this is the way allocation follows (or one of the ways at least). First the entrepreneur has to know what his business idea or his goal is and that tells him what e has to allocate and to look for. JP Aerospace for example need an engine - but there are chemical engines, ion engines, solar sails and so on. So they have to chosse one. They can rule out alternatives by what their vehicle will require and end up with an engine which provides impulse by accelerating ions. At that point the next level of details becomes relevant earliest. I simply didn't know yet that the term "ion engine" means a special kind of engine providing impulse by accelerating ions. The term includes no hint to that - for me at least.

So again Thank You Very Much for this clarification and explanation - I have to read the links but I suppose that I have meant elctric engines really in the brilliant-idea-thread as well as in the in-atmosphere-ion-engine-thread..



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

What about using the solar wind for an electric drive?

I think that solar wind is far off from going at constant intensity permanently but if it can be used to generate electricity for an electric drive a condensator might help to make a current got by the solar wind going constantly perhaps.

What about using shields like those under development for a lunar station? They woudn't have to be that large and crafty concerning what I have in mind I think.

The thought is to use the shield for Protons only while letting pass the elctrons. The protons would have to be kept away from the generator only - this special shield wouldn't be meant to protect the crew here.

The the electrons could pass to the generator and used there to generate electricity. That electricity could be used for an electric drive - as ONE source at least.

As far as I know from Physics the high speed of the solar wind should generate a higher current than slow moving electrons.

What about it? ...



Dipl.-Volkwirt (bdvb) Augustin (Political Economist)

Just this moment I wondered about a solution for the weight of electric engines. What about using the same solution as for cooling down engines?

As far as I understand the weight problem it has to do with the weight of the equipment that heats the hydrogen or another gas.

So what about using alreadyheated gas to heat the remainder also? May that this can be applied only if the engine has to be switched on long times and large amounts of gas are consumed.

Super-chilled liquid gas might cool down the engine first then heated by gas to be exhausted and then be exhausted itself.



What about that?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Chemical engines generally have excess heat. If you ran them full tilt most engines would melt, so you run them lean and you steal heat from them and put it elsewhere in the fuel cycle.

Actually, you usually run them rich, rather than lean. And it's not done because of excessive heat; our engines will run fine with the hottest stochiometric flame. We run rich because we have two tanks of the same size, and in that situation you get the best performance running equal volumes.

Rockets like the SSME run rich because throwing unburned hydrogen out the back improves the ISP of the engine significantly.