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> I think you need to understand that nuclear fission-powered
>interpret what you're saying below correctly, I think you've got that right.
Would it be possible to generate more eletrical power for the ion drive with a nuclear fission power plant to produce more eletricity on a space craft to increase the thrust but maintain the eficiency? i was under the impression that the limit in thrust of the electro static ion drive was due to the fact that it's sole power source are solar power arrays which can only pick up small amounts of energy from the sun for the drive. If a nuclear power plant could generate more eletrical power for the ion drive would this fix the thrust limitation problem?
> For your reference, a typical nuclear fission-heated
>gas drive can produce about 300-450 kN of thrust. Compare to the >space shuttle main engines which produce 1700 kN of thrust each and >the shuttle solid rocket boosters that produce 11,800 kN of thrust >each. Fission-powered rockets don't produce anywhere near that much >thrust, but because they can burn -significantly- longer (with Isp's >in the 1000 sec range), they are a superior drive system. Just keep >in mind the trade-offs -- the thrust is far lower than with chemical>rockets.
Shuttle SRB- Thrust = 11,800kN
- Isp =
Shuttle ME - Thrust = 1700kN
- Isp = ???
Fision Drive - Thrust = 300-450kN
- Isp = 1000s
> > But, I must point out that I think you are still a little >confused about ion drives. They are -nothing- like fission-power >drives. It is a completely different process. Ion drives are >totally electric. Could you maybe be thinking of an arcjet or >resistojet, in which an electric arc heats up a propellant and >accelerates it out? This is indeed somewhat similar (from a >conceptual standpoint -- not an engineering standpoint!) to a >nuclear-powered drive. The typical Isp for these drives is also >around 1000s, so they are about as fuel-efficient, but they do not >have anywhere near the thrust of a nuclear drive, as you point out. > Of course, you don't have to add all the mass of the reactor >shielding either, so there are trade-offs even here. > > An ion drive, however, is a completely different beast. With an >ion drive, you are accelerating charged particles directly, there is >no heating of an additional gas or anything. The amount of thrust, >as I indicated earlier, is very, very small, about a Newton (0.001 >kN). But the efficiency can be literally ten times that of a >nuclear-powered drive, so that's not to be sneered at. A plasma >drive, btw, is -not- a nuclear fission drive. A plasma drive is also >a kind of electric propulsion, but instead of just emitting charged >particles (and by the way, a "plasma" is nothing more than a stream >of charged particles), we accelerate those particles using a >magnetic field. Plasma drives are just one type of what we call >electromagnetic propulsion, whereas ion drive are one type of what >we call electrostatic propulsion. But please understand that >neither of these drives is anything like a nuclear-fission powered >drive. Both of these thrusters, the plasma and the ion drives, >produce very small thrusts at very high Isp's. You would only want >to consider electric propulsion for a very small subset of space >missions, basically very long-duration, long-distance missions. > > I really think what you are wanting is a nuclear fission drive, >as I outlined above. I think the confusion is probably nothing more >than your using one term when you mean another. NERVA (an >expendable drive) is the only prototype nuclear-fission drive that >has ever been built. A concept called CERMET (an advanced reusable >NERVA) has been proposed, but to my knowledge has never built. Deep >Space 1, as you correctly pointed out, uses electric propulsion, but >I don't think that is what you really want to use for the missions >you have in mind. If you have an engineering background, I'd be >happy to refer you to some papers that might help you design your >nuclear fission drive in Orbiter, just let me know! > >Hope this helps, >Kilo > >On Saturday, December 21, 2002, at 09:41 AM, DarkDAVE wrote: > >>plasma drives on the other hand also use ionized gas as propelant >>but have higher thrust, especialy if it has a nuclear fission plant >>as it's core. only reason current why ion drives have low thrust is >>because their eletrical power comes from solar radiation. plasma >>drives are like an ion drive connected to a high heat source rather >>than a low eletrical power source. >> >>----- Original Message ----- >>From: Keith Watt >>To: orbiter@firedrake.org >>Sent: Saturday, December 21, 2002 11:58 PM >>Subject: Re: Last point >> >>Hello all - >> >>I've hesitated to jump in here, but I think there is a >>misconception that needs correcting. I get the impression that some >>people on this list feel that ion drives are very fast, >>high-propulsion drives. Nothing could be further from the truth. >>What is wonderful about ion drives is that they are extremely >>-efficient- drive, having Isp's in the 2000-10000 secs range, but >>the thrust is at best on the order of 1 Newton (see Humble, Henry, >>and Larson, _Space Propulsion Analysis and Design_ for data -- I >>highly recommend this book if you have an engineering background). >>For comparison, just the maneuvering thrusters on the spacecraft I >>work with, 2001 Mars Odyssey, are 22 Newton thrusters. Ion drives >>produce a tiny, tiny, amount of force. You may have read that the >>exhaust velocities can reach 10,000 m/s, and that's certainly true. >>But remember that momentum is velocity * mass. The mass of these >>particles being ejected is beyond tiny, so the actual force >>produced is very, very small. You need to think of ion drives as >>being in the same category as solar sails, because that's what >>their orbits look like -- non-Keplerian spirals. >> >>So why use ion engines at all, you might ask? Because, as I said, >>their high Isp makes them phenomenally fuel efficient. That means >>that you can accelerate almost continuously. It takes years to get >>up to a decent velocity, but you can reach velocities chemical >>rockets can't, simply because they will run out of fuel first. You >>would never want to use an ion drive, for example, to escape Earth >>orbit or to travel to the Moon. It would take nearly a year to get >>there. Even Mars is a bit too close to really see a benefit, though >>you might could make a case for it. Basically, if you want to go a >>very long distance, electric (ion) propulsion is your best bet; if >>you want high accelerations, you'll never beat a chemical rocket. >>Also, if you are using ion propulsion, you'd better be extremely >>accurate in your piloting, because changing course is very, very >>difficult once you've built up some velocity over a couple of >>years... >> >>If you have any questions about it, I'll do my best to answer them. >>I am currently on the Mars Odyssey THEMIS Camera team, but before >>that I was a spacecraft design and mission analysis engineer at >>NASA/Marshall Space Flight Center. >> >>Regards, >>Kilo >>----------------------------- >>Keith Watt, M.A., M.S. >>2001 Mars Odyssey THEMIS Camera Team >>K.Watt@asu.edu >> >> >>On Saturday, December 21, 2002, at 02:35 AM, Dark DAVE wrote: >> >>Ever heard of Deep Space 1? that's a retired ion drive satelite. >>It's the 2nd of it's kind and is now has been manualy shut down in >>space. It also took photos of a comet, and then an asteroid. >> >>A plasma drive prototype already exist, i think it belongs to JPL, >>not sure, but it is working on the ground quite well... it's only a >>matter of time before they build one in a space craft. A plasma >>drive works almost the same as an ion drive, but it uses heat to >>propel the ionized propelant. >> >>do a search on google.com for Deep Space 1. >> >>David >> >> >> >> >From: "Technician" >> >> >Reply-To: orbiter@firedrake.org >> >> >To: >> >> >Subject: Re: Last point >> >> >Date: Fri, 20 Dec 2002 13:23:20 -0600 >> >> > >> >> >Well, what I meant by not being realistic is that, as far as we >>know, there >> >> >is no working ion drive spacecraft prototype in NASA's inventory. >> >> >:) >> >> >-----Original Message----- >> >> >From: DarkDAVE >> >> >To: orbiter@firedrake.org >> >> >Date: Thursday, December 19, 2002 11:03 PM >> >> >Subject: Re: Last point >> >> > >> >> > >> >> > >Sounds interesting! I'll have to read up on the centurion >>manual. So you >> >> >say >> >> > >it's not realistic? I am only interested in realistic models, >>even if it's >> >> > >hypothetical it can still be realistic if the manual indicate >>where all >> >> >that >> >> > >thrust and fuel come from and how it's produced in real life >>using real >> >> > >physics maths and models. >> >> > > >> >> > >I fully intend to make my own nuclear powered plasma drive ship >>my self >> >> > >(plasna druve us an ion drive that heats up the ions). And ill >>back up all >> >> > >the performance specs with a technical manual to indicate how >>it can work >> >> >in >> >> > >real life. I might have to use some of NASA's current designs >>for going to >> >> > >Mars. >> >> > > >> >> > >Just out of interest has anybody modeled the X-33 or the X-43A? >>The X-33 >> >> > >program failed, but the X-43A as i recall is a scramjet/rocket >>hybird ship. >> >> > > >> >> > >Not sure if i can answer your question tho, ill leave it to >>some one else >> >> >to >> >> > >do so. >> >> > > >> >> > >David Ong >> >> > > >> >> > > >> >> > >> The Centurion 2069 ship I imported into Orbiter is set up for >>'ion drive' >> >> > >> engines. Capable of velocities well over 250Kps. Atmospheric >>flight is >> >> > >> obtained by conventional airfoil wings, control surfaces and >>rudders. >> >> > >> However, I have to mount much smaller engines for slower >>flight speeds, >> >> > >> since the primary engines put out way too much thrust to >>control landings >> >> > >> very well, even in Earth's gravity and atmosphere, extremely >>difficult to >> >> > >> control when landing on the Moon or other low >>gravity/atmosphere >> >> > >> planet/moon. >> >> > >> >> >> > >> In this configuration, going to Brighton Beach Moon base from >>Cape >> >> > >Canaveral >> >> > >> takes about an hour or so at 120Kps. Slowing down is not a >>problem, OI is >> >> > >> not a problem. Next test is to fly from Brighton Beach to >>Olympus, Mars, >> >> > >at >> >> > >> a test speed of 200Kps. >> >> > >> >> >> > >> Ok, so it isnt following real world scenarios. But, all >>things advance. >> >> > >NASA >> >> > >> has re-opened the space nuclear power research and soon we >>could see >> >> > >either >> >> > >> the shuttles or shuttle replacements powered by nuclear >>reactors, which >> >> >in >> >> > >> turn provides plenty of juice for HV ion drive engines. >> >> > >> >> >> > >> I do have one inquery. Is there a way to have such a high >>velocity ship >> >> > >have >> >> > >> retro thrusters that automatically adjust their density >>output based on >> >> > >> velocity, and adjust themselves as the velocity changes? Can >>this be >> >> > >applied >> >> > >> to the retro, pitch, bank and yaw thrusters as well? Will the >>engine in >> >> > >the >> >> > >> sim run such engines in this manner? >> >> > >> >> >> > >> RFB >> >> > > >> >> > > >> >> > >-- >> >> > >Orbiter discussion list: >> >> > >- mail orbiter-request@firedrake.org with subject "unsubscribe" >>to leave >> >> > > or ask the listmaster (@firedrake.org) >> >> > >- archives at http://lists.firedrake.org/orbiter/ >> >> > > >> >> > >> >> > >> >> >-- >> >> >Orbiter discussion list: >> >> >- mail orbiter-request@firedrake.org with subject "unsubscribe" >>to leave >> >> > or ask the listmaster (@firedrake.org) >> >> >- archives at http://lists.firedrake.org/orbiter/ >> >> >> >> >>