Future propulsion systems?

Just wondering what the people here see as the future for propulsion systems? So far it seems to be mainly liquid/chemical rockets? but surely as we start to shift towards a stage where re-usability is an important consideration. And where we wish to send probes farther into space. The sheer amount of fuel that would be needed makes them less practical? So whats the future?

Well, if you knew the answer to that.......

The obvious near term one is nuclear propulsion, but you still need loads of fuel.

VASIMR

VASIMR, HDLT (Helicon Double Layer Thruster)

The anti-matter propulsion drive has potential, but there are quite a few issues with it. Someone with more expertise will be of more use than I, I will have to go and do a bucket of research on it before I form an actual opinion on it.

I would like to see something with more thrust. These ion thrusters are very efficient, and while VASIMR is hailed as a high-thrust ion thruster, that is still an extremely relative term. We're talking about a maximum thrust with the current models that's not enough to get my lunch up into the air, let alone a space ship. So these engines are useless for getting off-planet more cheaply, which is still our main problem in space flight. For unmanned deep-space exploration these things are useful, if you can cut down travel time from over a decade to a few years for example. But for humans, being stuck in a tin can for a few years is already a lot. VASIMR isn't going to zip us back and forth to Mars in a few weeks.

So my vote goes to nuclear, in particular nuclear light bulb type designs. Of course there are all sorts of political problems with anything nuclear, so this may never actually come to be, but from a technical perspective...

Nuclear thermal. It's been tested, and it works.
http://en.wikipedia.org/wiki/NERVA

Phase-shift Plasma Turbine
http://www.youtube.com/watch?v=GSkxPghXTCg

Relativistic Space Drive
http://www.youtube.com/watch?v=sgAwyr5Udzw

nice videos, but are those things even possible according to our current understanding of physics? There where a lot of "probably" in the texts...

As far as getting off-planet you're pretty much restricted to chemical, nuclear, or space elevator.

There's some experimental new chemical fuels that could potentially deliver isps approaching nuclear thermal - stuff known as "High Energy Density Materials" HEDM. This includes weird *** like metallic hydrogen and dodecahedral nitrogen. Still, these fuels are at least 20 years away.

The nice thing with deep-space propulsion systems like VASIMR is they provide a way to convert electricity directly into thrust. With a 10MW nuclear reactor you can send a very large ship from LEO to Mars orbit using VASIMR and have it complete the journey in a measly 2 months. Even a good nuclear rocket can't really beat that. You have to get into the speculative realm of fusion propulsion in order to get the trip time down to a matter of weeks and that isn't even worth mentioning or wasting time on as a practical solution in the foreseeable future.

As to antimatter - Alpha at CERN has captured what? Like 80 antihydrogen atoms at a time? Sure, we know how to "store" it now (magnetic octupole moment ftw), but good luck getting a practical antiproton decelerator working well enough to make macroscopic amounts of the stuff.

We're getting ready to fire a hybrid chemical/electrical engine. We're just upgrading the sensors and load cells. We should be just a few weeks away.

JP

http://www.jpaerospace.com

How does that work?

Bob Clark

A little while ago they were experimenting with solid model rocket motors and rare earth magnets to make an MHD electrical generator. So I'm guessing it will be a rocket motor with a magnetohydrodynamic "afterburner", i.e. the same setup but now with current being passed in. It will be interesting to see how much extra exhaust velocity that gives...

Robert Zubrin on VASMIR: http://www.marssociety.org/home/press/tms-in-the-news/thevasimrhoax In short, Zubrin claims that current ion thrusters have ~70% energy efficiency, and VASMIR only has ~50%.

I think that improved ion thrusters with 70 km/s exhaust and solar cells will be the preferred mode of slow, cheap transport in the inner solar system for quite some time.



I'm glad to see JP Aerospace is still working on a balloon to orbit. I hope it can work on Venus and Mars too.

The engine is a hybrid with an antenna wrapped around it. The chemical reaction creates the plasma and it's then pumped with RF. It's like a two staged ion engine where the first stage uses a helical antenna to create the plasma and a second antenna pumps it before accelerating it. We have substituted the first stage antenna for a chemical process. It dramatic decreases the electrical power requirement.

It's a dual mode motor with the RF portion off it's a traditional chemical engine and we use the MHD to convert the chemical energy to electrical. This combination of modes matches our requirement in the powered ascent profile for Airship to Orbit. High thrust, low efficiency and high electrical power generation when we need it and low thrust, high efficiency when we need it.

We have pretty humble goals for this first motor. We want to turn it on, have flamey stuff come out the back, induct RF into the plasma (not just shoot it in but actually induct into the plasma) and see current in the MHD generator on the back side. On the ion engine scale it's a 800 watt engine and the rocket side it's about a "J" motor. We've instrumented the induction, the thrust, the electrical power input and the electrical output.
The plasma accelerator doesn't go on until the second version this winter. It was too much to add it to this one. It's a very crude first generation, but the need to start somewhere.