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#26 2002-05-01 11:31:54

C M Edwards
Member
From: Lake Charles LA USA
Registered: 2002-04-29
Posts: 1,012

Re: Plasma Rockets - Where do you stand on this topic?

Gee.  My psychic powers have been revealed.   wink

Seriously, though, why would we not go to Mars and keep going, given a practical plasma rocket engine?

CME


"We go big, or we don't go."  - GCNRevenger

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#27 2002-05-01 20:15:38

Josh33086
Banned
From: Norwalk, CT
Registered: 2002-01-21
Posts: 11

Re: Plasma Rockets - Where do you stand on this topic?

Although nucluar fussion would be faster than conventional rockets it would still take a least four to six months. I have done some advanced study on the safety asspect. I have found that most if not all nucluar power accidents (ex.Three Mile Island, Chernobyl) were caused by human error. So for long term power output nucluar energy MAY be the best. But if nucluar power is chosen I feel that the astronouts must be trained to the enth degree. What do you think?

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#28 2002-05-02 11:57:36

GOM
Member
Registered: 2001-09-08
Posts: 127

Re: Plasma Rockets - Where do you stand on this topic?

Gee.  My psychic powers have been revealed.   wink

Seriously, though, why would we not go to Mars and keep going, given a practical plasma rocket engine?

CME

Why would we not?

That is quite a question....

After seriously observing our space program for over 30 years, I no longer believe we have a technical problem holding us back.  I believe it is a political problem.

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#29 2002-05-02 11:59:40

GOM
Member
Registered: 2001-09-08
Posts: 127

Re: Plasma Rockets - Where do you stand on this topic?

I have done some advanced study on the safety asspect.

Have you done any study on nuclear subs?

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#30 2002-05-02 14:39:16

Canth
Member
Registered: 2002-04-21
Posts: 126

Re: Plasma Rockets - Where do you stand on this topic?

Actually I said that you should use an earth based microwave transmitter for atmospheric ascent (taking a few minutes) and once in space deploy solar panels for power.
      A mission isn't possible within the current world production   having to use chemical power for all power the entire time. You would literally need millions of tons of fuel. You have to use solar or nuclear (fusion or fission) power somewhere along the line or you have to carry chemical fuel for heating/cooling, other life support, cooking, communication, lighting. You name it it uses power. Not only that but you must launch shield and store the fuel increasing the amount of fuel needed. The mission blows way out of proportion.
        Also currently no viable electric power generation system exists based on fusion (other than using fusion produced sunlight). However fission reactors work quite well and would be perfect for a mars mission.

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#31 2002-05-02 15:12:51

Josh33086
Banned
From: Norwalk, CT
Registered: 2002-01-21
Posts: 11

Re: Plasma Rockets - Where do you stand on this topic?

I have an idea, please tell me what you think. What if we took a spacecraft and slowly, useing current means, lifted to the highest possible earth orbit. Than start a inward orbit(getting closer and closer to earth) therefore building speed and pottential energy. Than when we are as close as possible we shift orbit and head toward mars. This just an idea in the making i know we would still have to get back. Oh and no I have not done much research on nuclear subs but don't recall any castrpic failures not related to human error.

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#32 2002-05-02 18:45:06

Phobos
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Registered: 2002-01-02
Posts: 1,103

Re: Plasma Rockets - Where do you stand on this topic?

Seems to me that you if you gained any significant speed from spiraling toward Earth, you'd probably just waste the extra energy you created trying to get back out of low orbit to where you were in the first place.


To achieve the impossible you must attempt the absurd

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#33 2002-05-02 21:37:33

Canth
Member
Registered: 2002-04-21
Posts: 126

Re: Plasma Rockets - Where do you stand on this topic?

I think this would take a long time and not provide much extra thrust. However I beleive it is basically the same as a gravitational assist which allows you somewhat more bang for your propellant buck. Gravitational assists work better when coming from outside the planets gravitational domain and when the planet is larger (like Jupiter). A gravitational assist with jupiter was used on all the outer planet probes I believe (the voyagers and the pioneers). It is also worth more if you are going a longer distance as a slight increase in velocity subtracts more time from a longer trip then a shorter one.

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#34 2002-05-03 10:35:04

Josh33086
Banned
From: Norwalk, CT
Registered: 2002-01-21
Posts: 11

Re: Plasma Rockets - Where do you stand on this topic?

So much has been made over different propulsion systems. I think that we should all work on one plan. If we start with the time we would like to take each way, such as 90 days, than go from there. figure 36 million miles to mars you need to go like 16,000 mph. So now we make a proplusion system to match. With Zubrins plan we can build a huge rocket to go home with.

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#35 2002-05-03 14:23:26

Canth
Member
Registered: 2002-04-21
Posts: 126

Re: Plasma Rockets - Where do you stand on this topic?

six months each way is more fuel effecient. Actually I beleive it is the most fuel effecient route to mars (and back) in a reasonable time frame. Thus it would be cheapest to use a six month time period.

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#36 2004-06-23 17:09:14

jpeachman787
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From: Ohio, USA
Registered: 2004-05-30
Posts: 6

Re: Plasma Rockets - Where do you stand on this topic?

I sincerely appologize if I say anything that has already been said. Time is something that I don't have a lot of, so I can't read the last few pages of this very interesting topic.

I think plasma rockets (especially fusion rockets) are extremely exciting smile However, why do we need to fund them now? There's no real commercial use for them now, we can't even reach orbit cheaply (yet). I do not think its cost effective to underfund a project for 10 years to get a head start on the technology. We won't know when we need the rockets untill about 5 years before we really do, and I don't see why the technology can't be created in just a few years. Sure, plasma physics is extremely complicated, but many highly advanced technologies have been perfected in extremely short periods of time by the application of sufficiant resources, and the collaboration of the best people in the particular field. The best way to gather these people, and the money, is when u plan to use that technology very soon, and that isn't untill a few years before we finally need it!

Half-developing technology without actually planning to use it is the way NASA does things. Building things as you need them is what private industry does. As far as I'm concerned, NASA hasn't done a whole lot for me, but private industry has and will continue to do so. Private Industry will never sell nuclear fission rockets en masse because the materials can be used to make nuclear weapons. Fusion fuels, on the other hand, cannot be used to make a bomb, so I do think a future millionaire (a century hence?) may be able to buy his/her own private fusion-powered space yact smile Wow, wouldn't that be nifty?

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#37 2004-07-09 19:53:15

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Plasma Rockets - Where do you stand on this topic?

Do not be so quick to assume that fusion fuels are harmless of themselves... it is not outside the realm of possibility to make a nuclear bomb with only fusion fuels. The military can get fairly close now by using conventional explosives to initiate the reaction, by the time we have need for an advanced rocket like this, then it might not be hard at all...

"Half developing a technology" and such is a chicken/egg, unless you have the technology available to do an application, then chances are there won't be any large investment in said application. This is where gov't funding of technology research comes in, since the gov't doesn't need to turn a profit off a research venture like a business has to.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#38 2004-07-10 03:11:18

JimM
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From: England
Registered: 2004-04-11
Posts: 247

Re: Plasma Rockets - Where do you stand on this topic?

Do not be so quick to assume that fusion fuels are harmless of themselves... it is not outside the realm of possibility to make a nuclear bomb with only fusion fuels. The military can get fairly close now by using conventional explosives to initiate the reaction, by the time we have need for an advanced rocket like this, then it might not be hard at all...

Using HE? For a bomb, perhaps, but as a means to propell a rocket...? I thought the main line of thinking there was to use lasers to compress a pellet to critical density and temperature, and so initiate fusion? The trouble with conventional explosive would be that, yes, you can create an implosion, but can you keep doing it several times a second over long periods in your blast chamber-cum-rocket exhaust? And you'd need to carry quite a mass of HE, while the laser system could be powered by the previous fusion 'burst'.

The laser route is much 'sweeter' engineering, is it not?

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#39 2004-07-12 15:05:29

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Plasma Rockets - Where do you stand on this topic?

Mentioning pure-fusion type nuclear warheads in response to an above statement that fusion energy in general, reactors imparticularly, is safer from a security standpoint because you "can't make nukes with it, you need U/Pu" ...which unfortunatly may not be true for much longer. It may be possible to do it with conventional explosives or a magnetic constriction from one of those exploding coil generators (see EMP warheads), no U/Pu necessary.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#40 2004-07-21 22:50:19

comstar03
Member
From: Australia
Registered: 2004-07-19
Posts: 329

Re: Plasma Rockets - Where do you stand on this topic?

Well,

The first issue that have to get over is the treaties signed by the space based countries that prohibit nuclear weapons or military weaponry, military personnel, in space or on celestial bodies. These treaties need amending, redefining and updating.

Also

We need proper facilities for safe testing of these drive systems and use mockup spacecrafts and also development of control systems and also design these systems to be easily repairable in outer space.

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#41 2004-07-22 12:48:27

JimM
Member
From: England
Registered: 2004-04-11
Posts: 247

Re: Plasma Rockets - Where do you stand on this topic?

six months each way is more fuel effecient. Actually I beleive it is the most fuel effecient route to mars (and back) in a reasonable time frame. Thus it would be cheapest to use a six month time period.

The most fuel-efficient transfer time to Mars is 260 days which is the duration of a Hohmann transfer ellipse at time of closest conjunction of Earth and Mars. Return transit time is the same.

The whole story is set out in painful mathematical (and German) detail by a certain Herr Professor Doktor Wernher Freiherr von Braun (he was made up to professor by Hitler, so he did not go on about that) in a jolly little booklet called Das Marsprojekt he published in 1952. There was no talk of using any form of nuclear rocket, or even high-Isp chemical rockets like LH2/LOX. LH2 has a high boiloff rate in vacuum, which could have been embarrasing when time came to go home, to find the tank was empty. No, von Braun wanted to use nice sensible hydrazine and nitric acid...

And so it goes on. The point von Braun was making, more than fifty years ago, was that even then we already has the technology to go to Mars. All it needed was the will to do it, and that's still lacking in certain quarters today.

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#42 2004-07-22 13:50:42

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Plasma Rockets - Where do you stand on this topic?

Mmmm I would NOT say the technology was available yet... yes the actual hardware could be built to fly to Mars back then, just not without completly obliterating the gross product of the whole country for years. For a technology to be "available," it has to be at least somewhat affordable. His scheme was more of a thought experiment than a real plan...

Relying on long-term storage of Nitric Acid kinda worries me... may I point out there are a large number of rockets that use this fuel combination... Russian SLBMs. And as i'm sure you are aware all the fun they have had with those... sunk what, two submarines? "Sensible?"

A nuclear drive is not an absolute must for a Mars expedition... but it would be great for getting us away from the cut-toothbrush-handles-off thinking without making the vehicle unreasonably large, and I think some kind of nuclear drive will be nessesarry before we can do much more than set up a little science outpost... you can forget about manned trips to Jupiter or Saturn without an advanced (1000's of sec. Isp) drive.

Hydrogen does boil off quickly if you leave it in the sun or with pipes that you can't isolate, but its boiloff can be managed with a solar shield and clever plumbing; the SIRTF facility stores liquid Helium and it is boiled off intentionaly to keep the thing cold, and that tank will last for years. A little boiloff can be compensated for I believe with a small condenser too.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#43 2004-07-22 15:13:01

PurduesUSAFguy
Banned
From: Purdue University
Registered: 2004-04-04
Posts: 237

Re: Plasma Rockets - Where do you stand on this topic?

From everything I've raid now matter if you go the route of a plasma drive or nuclear thermal you are going to need a Fission Reactor. For nuclear thermal the need for the reactor is to heat the reaction mass, in a plasma rocket it's the generate electricity to power it. So what the question really comes down to is which is the more efficient use of nuclear power in space.

I think the trick would be to combine the two options. Design a NTR that can also operate as a generator, use a limited amount of reaction mass through the NTR for trans mars interjection then switch over to producing power for an electric plasma drive be it VASMIR or perhaps some sort of IC Fusion device to accelerate to half way and then decelerate to cut the trip time in half. Once you aerobrake and are on the surface I suppose it would be possible to tank in new reaction mass and use the NTR to ascend to orbit and return to earth in the same fashion.

Does the idea of a hybrid NTR/Electric drive make sense? Comment, Questions, Concerns?

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#44 2004-07-22 15:31:50

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Plasma Rockets - Where do you stand on this topic?

Mmmmm not real practical... the kinds of reactors you need to generate megawatt-range quantities of electricity are much different then ones used for solid-core NTR engines.

The biggest difference is size... the NASA DRM-III mission calls for tiny engines with just 15,000lbs of thrust each and be light as possible, since the nuclear TMI stage has to ride with the launcher for the Mars payload.

To maximize the amount of electricty per pound, you need an entirely different internal arrangement in the core to circulate liquid metal efficently and slowly, not for squirting in ultracold liquid hydrogen at extreme speeds

The large radiator size needed for a powerful conventional nuclear reactor requires the high Isp of the electric drive to operate through the whole range of the mission, otherwise it would be too heavy. NTR nuclear reactors are cooled by the propellant itself.

Gas core thermal rockets or gas core nuclear reactors, the next generation in nuclear propulsion, are completly incompatible.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#45 2004-07-22 19:04:52

JimM
Member
From: England
Registered: 2004-04-11
Posts: 247

Re: Plasma Rockets - Where do you stand on this topic?

Mmmm I would NOT say the technology was available yet... yes the actual hardware could be built to fly to Mars back then, just not without completly obliterating the gross product of the whole country for years. For a technology to be "available," it has to be at least somewhat affordable. His scheme was more of a thought experiment than a real plan...

You're right and wrong at the same time...

It's not hard to show that the Peenemünde A-4/V-2 project actually used up as much a proportion of the German war economy as the Manhattan Project did of the US war economy--and in the end it delivered upon the enemy rather less bomb-load than one typical nightime raid on Germany by 500 RAF Lancaster bombers, so in terms of who got best value for money there, it most certainly was not the Germans. Yet without Peenemünde, I doubt we would even be where we are today so far as space travel is concerned, so from that perspective it was worth every penny.

Von Braun did cost his Marsprojekt. He forecast it would cost $4 billion, in 1952 money. He described that as the price of a small war.

Well, as we can see from his earlier venture in Germany, he did tend towards the optimistic side when it came to pricing his proposals. But even so, it would not have obliterated the entire GDP for years.

Now, talk of fission or fusion powered rockets is interesting for the future--and the same is true of practical/useful plasma rockets. But what I think we should be aiming for now is a manned expedition to Mars that does not require us to invent anything new; in other words, a mission profile that fits within known technology.

Which is what von Braun did 52 years ago. But yet of course, it was a thought experiment; an engineering paper setting out how it could be done with current echnology; a theoretical demonstration that the idea need not be science fiction.

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#46 2004-07-22 19:45:35

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Plasma Rockets - Where do you stand on this topic?

Well you get the idea... if the technology is not efficent enough, then it is impractical. Though I wonder what would have happend to England if Hitler had put Tabun instead of explosives on the V-2... gas masks would only prolong your agony.

I think Von Braun's estimation about how hard it would be is extremely optimistic when looking at such a scheme in hindsight... so much so that it really does relagate the idea to a thought experiment instead of a workable plan.

Anyway, back to atomic rockets... We do not HAVE to have anything better than LOX/LH rockets to put small numbers of people and small payloads onto Mars and retrieve them. But with such a limitation, it isn't easy and weights will have to be cut to the bone with no margin for the dread weight creep... Or you have to start launching the payload + LH and the TMI + LOX on seperate boosters, increasing the price, the complexity, and the risk for a Mars sortie... and if you can't launch fast enough, the launch window would become an issue.

Which is where NTR rockets come in... we have built them before, both the old NERVA graphite/ceramic/rare earth reactor and some work was done for the USAF on a more efficent Uranium Carbide reactor to boost the capacity of the Titan-IV arcitecture or possibly a LEO-GEO NTR tug. We would not need huge giant mega rockets, but three or four small 15,000lbs rockets weighing only hundreds of pounds each or one modest sized 45,000lbs engine weighing only a few thousand kilos tops.

That would increase the TMI throw mass by about 50% direct from Earth or LEO, which would really loosen up the weight restrictions for the Mars ship. No more having to cut your toothbrush handles off... Using them avoids one of the cheif failings of the MarsDirect program, that if anything got heavier than it should be, there is no way Ares could lift it in one go.

Or as in NASA DRM-III, you can afford the same payload using a launcher (MSFC Magnum) only 2/3rds as powerful as Ares. Pairing this launcher or another "Shuttle-C" concept with the new 5-segment SRBs and increasing its payload from 80MT to 100MT without having to go all the ways to Ares... this combined with NTR engines will give a Mars payload several extra tons to play with... solid gold for engineers.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#47 2004-07-22 20:10:09

Scott G. Beach
Banned
Registered: 2002-07-08
Posts: 288

Re: Plasma Rockets - Where do you stand on this topic?

Shaun:

You wrote, “If the choice is between a coal-burning power station and a nuclear plant, we are probably better off with the latter.”  According to the U.S. Department of Energy, the geothermal energy field under Nevada contains enough energy to power our ENTIRE civilization for thousands of years!!!  So please don't let politicians (e.g., George Bush and his oil men) tell you that we have to drill oil wells in the Arctic Wildlife Preserve.

According to Dr. Marvin Herndon, the Earth's core is made of uranium.  So geothermal energy is really a form of nuclear energy.  See http://www.nuclearplanet.com]http://www.nuclearplanet.com


"Analysis, whether economic or other, never yields more that a statement about the tendencies present in an observable pattern."  Joseph A. Schumpeter; Capitalism, Socialism and Democracy, 1942

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#48 2004-07-22 20:22:18

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Plasma Rockets - Where do you stand on this topic?

Problem: Putting the power station too far away from the customer is impossible, because of the loss of energy by power line resistance. A centralized geothermal plant "farm" is not practical for this reason.

Problem: Putting all the power plants in one place invites our enemies to obliterate our nation with a single nuclear strike. With our ability to produce energy gone for years.. all electricity and transportation nationwide.. the United States would cease to exsist in a single day.

Problem: Capital investment to replace all power generation plus transportation energy needs by geothermal plants would be trillion-dollar undertaking. Our economy could not possibly absorb this cost over a short period.

Problem: Making cars, trucks, trains, and airplanes operate from electricty or from hydrogen created by electrolosys of water by electricity is not yet practical. It would also take decades for our nation to switch to Hydrogen or other energy storage medium. Reliance on fossil fuels for transportation (and to operate gas fired power plants) will not go away for decades no matter what we do.

Problem: The world's current capacity to pump oil is somewhat limited economicly speaking and is becoming a national security concern. It is in our nations' interest to increase domestic supplies of oil in the short term... and a nontrivial quantity happens to be under the ANWAR. Modern drilling techniques are relativly nondestructive ecologicly speaking, and enviromentalists' concerns are at best shakey... which compared to the interest of national security and economic wellbeing makes them essentially... irrelevant.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#49 2004-07-22 21:15:25

BWhite
Member
From: Chicago, Illinois
Registered: 2004-06-16
Posts: 2,635

Re: Plasma Rockets - Where do you stand on this topic?

Problem: ANWR has become a hot button issue for BOTH sides and symbolism outweighs reality, for both sides.


Give someone a sufficient why and they can endure just about any how

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#50 2004-07-22 21:27:11

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Plasma Rockets - Where do you stand on this topic?

When the economists come to the congressional comittee and say that ANWAR will knock a dime off of gas prices and allow us to squeeze Opec a little on price (especially with Iraqi oil coming in)... That might evaporate real quick.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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