space challenge

wick07 · Mar 27, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>I think Nuclear Rocket engines are the future.  We have pretty much reached our limit with chemical engines.  Yeah, we can squeeze a bit more juice out of them, but if we really want to explore space we need to improve our engine by orders of magnitude------------------------------------------------------------------------------------------ Read the post above!! The boosters are not that much smaller using nuclear .And really is no good for doing earth orbits.Going to the moon or mars is where the nuclear rocket comes in!! But its does not seem to be that powerful.Wow the Ariane V sure looks cool!! They seem to have a potential in the UK for man space in the UK , using the Ariane V.But problem seems to be the government not interested. Posted by nec208</DIV> Wow, do you own stock in a company that makes liquid H2 and LOX?<img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-laughing.gif" border="0" alt="Laughing" title="Laughing" />  It is true that their are limits to nuclear thermal rockets.  Yes a solid core NTR has an ISP of between 800-1000, and that is only double what a chemical rocket can do.  The point I was making is that we are already at the upper range of what chemical rockets can give us, they are a very mature technology.  However the solid core NTR (like NERVA) is only the beginning of what we can do with nuclear rocketry.  So what we are comparing is the lower end of the nuclear spectrum (NERVA) to the upper end of the chemical spectrum.  So what I am saying is that the most basic design nuclear rocket is ALREADY DOUBLE the upper reaches of what chemical has to offer.  A Gas Core Nuclear Rocket (GCNR) is a significant improvement over a solid core and could offer much higher ISPs.Bottom line, remember when you are comparing nuclear and chemical rockets that we already have a very good idea of what chemical rockets can do and that we are barely scratching the surface in the nuclear field and already can offer twice the ISP.  It's still early to count them out even, if I may humbly add, as launch vehicles. <div class="Discussion_UserSignature"> _______________________________ "If you are surrounded by those who constatly agree with you, then you're in an intellectual vacuum. If you feel like trying to make a difference, you have to BE different. How can you do that without interacting with those who are different from yourself?"- a_lost_packet_ </div>

mako71 · Mar 27, 2008

Sure, fission rockets would have better ISP compared to chemical ones, but I still think that the ISP is not the only thing making lauches so expensive. As mentioned above, nuclear rockets are probably a viable alternative in future when the mission is going to outer space, since then there is no danger about radioactive contamination.But how about using them for launch vehicles from Earth to LEO? A few questions arises in my head;1) Manned or unmanned? Lifting unmanned cargo to LEO would probably have a benefit that there is no need to that heavy shielding of the reactor.2) Expendable or reusable? Expendable ships will come back to atmosphere in some time, that is, the radioactive particles will be spread to large areas. Reusable vehicles (which may bring the radioactive core back safely) are more expensive and have more structural mass - that's why the current shift is to expendable multi-stage rockets... <div class="Discussion_UserSignature"> ________________ reaaliaika.net </div>

qso1 · Mar 27, 2008

For Earth-Mars -system, right?Correct, 26 month line up for chemical, even firts generation nuclear thermal propelled missions to and from mars. Really? I thought, that oxidier together with hydrogen form propellant, and that it is the exhaust velocity of _propellant_ combined with amount of it that which tells the end velocity of the payload (v = ln(m[full]/m[empty])*v[exhaust]).In chemical rockets this is true. The nuclear thermal NERVA type or solid core rocket works by passing fuel such as LH2 thru the nuclear reactor, no separate oxidizer as the nuclear core apparently serves this purpose though they refer to it as fuel. I found a link that breaks down the basic rocket types and how they work. Otherwise, the cost and use of expendables is no better than it was in the 1960s.http://en.wikipedia.org/wiki/Nuclear_thermal_rocketAbout the subject itself; surely accessing LEO is the most expensive phase in space travelling. I think that nothing can change it, meaning that also in long run we need to think what to launch to LEO - that is, although it may became cheaper with advanced technology, it is still going to be relatively expensive, meaning that we probably want to exploit space materials in space rather than launch everything from the surface.This is true, we will want to eventually exploit materials from such places as asteroids and the moon but we still have to get the stuff up there to do the exploiting. This is where private industry space efforts come in. If they could cut the cost of getting to low orbit by just half, that would be a significant improvement."optimal" launch vehicle may be reusable 3STO; the first stage uses turbine engines, the second one SCRAM-jet and the last stage uses chamical rockets. The last stage may be disposable, and only the crew cabin is shielded to re-enter to atmosphere.It may take private enterprise to build something like a 3STO to prove the concept both technically and economically. The reason for this is that in this way the atmosphere oxygen can be used as a part of propellant, saving some mass. I know that these designs are currently not the most interested, since there is a shift to simple disposable rockets due to several rational reasons, e.g. flight frequencies.Designs such as 2 or 3STO or SSTO were supposed to solve the flight frequency problem. The problme in bringing them about is up front development costs run higher the more advanced the proposed technical solution. So, all in all, I think that the expensiveness of space flights is not entirely solved with any technological solutions, but it is more a question of economics and advances in other technology than launch vehicles (e.g. robotics). We may make accessing the LEO cheaper of a magnitude with some ways; (1) using inexpensive, easily storable propellants, (2) decreasing the labor costs (in building a spaceship, as well as when preparing it to be relauched), (3) reusing all that can be reused, and so on. But still, LEO access will be expensive. You are free to disagree, since I haven't thought these issues very deeply; I'm open for any comments.  Posted by mako71Actually it appears you thought it through quite well and I agree with much of it. I think its going to take a private industry effort since it seems NASA can never get the budgets needed to finance up front cost of developing an inexpensive reusable solution to low orbit. Government does not operate as efficiently as private industry despite NASA being one of the more efficient agencies in government. <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

qso1 · Mar 27, 2008

Wow, do you own stock in a company that makes liquid H2 and LOX?  It is true that their are limits to nuclear thermal rockets.  Yes a solid core NTR has an ISP of between 800-1000, and that is only double what a chemical rocket can do.  The point I was making is that we are already at the upper range of what chemical rockets can give us, they are a very mature technology.  However the solid core NTR (like NERVA) is only the beginning of what we can do with nuclear rocketry.I agree completely. But its cost that will ultimately determine how much of an advantage nuclear over chemical is when operated endoatmospherically. The cost of taking two to three years to build test and check out each nuclear upper stage. The cost of the nuclear expertise required. If the nuclear rocket stages could be recovered and reused, the equatiion could change considerably. So what we are comparing is the lower end of the nuclear spectrum (NERVA) to the upper end of the chemical spectrum. Exactly.So what I am saying is that the most basic design nuclear rocket is ALREADY DOUBLE the upper reaches of what chemical has to offer.  A Gas Core Nuclear Rocket (GCNR) is a significant improvement over a solid core and could offer much higher ISPs.If the nuclear rocket stage is pound for pound, exactly double, then the investment may be worth it. But I'm figuring the added weight of sheilding and the weight of the reactor etc. is going to cut into some of that valuable ISP. In effect, making a nuclear stage with 800 ISP the equivalent of a 650 ISP stage after the added weight penalties are factored in. Solid core nukes are the simplest to build. Gas cores get more complex...added expense but have much higher ISP. If I were going to go with a nuclear upper stage, I'd go with gas core so long as its reusable, or somehow built at no greater cost than (And are no danger from a radioactive exhaust fallout standpoint) chemical stages. Bottom line, remember when you are comparing nuclear and chemical rockets that we already have a very good idea of what chemical rockets can do and that we are barely scratching the surface in the nuclear field and already can offer twice the ISP.  It's still early to count them out even, if I may humbly add, as launch vehicles. Posted by wick07.Bottom line is the dollar. So long as we continue government funded spaceflight. NERVA was well on its way to becoming an operational rocket in the late 1960s until it smashed into the cost barriers erected by the public, press and Nixon Administration in the early 1970s where it has remained since.The biggest difference in our debate stance is that I favor nuclear stages for unmanned and manned deep space propulsion while your saying you think nuclear stages will have to replace chemical stages for endoatmospheric use, which I'm not strongly in favor of.Almost forgot, I don't own stock in any companies, not well heeled enough or financially astute enough to play that game. I wouldn't mind owning stock in aerospace, but I'd diversify my portfolio if I did. <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

qso1 · Mar 27, 2008

Sure, fission rockets would have better ISP compared to chemical ones, ISP is not what makes the launch vehicle expensive. Its the manpower and method by which we pay for them (Gov contracting) and they are more expensive number 1 because they are expendable. If a nuclear propelled upper stage were expendable, its added complexity would make it more expensive than chemical. Otherwise, we'd already have nuclear stages in operation somewhere.A reusable vehicle could bring back its radioactive core because its not expendable. But if the vehicle suffers a failure and falls short of orbit and burns up, your still going to spread radioactive material into the environment. This is why I think it best to use whats proven endoatmospherically, and save the nukes for deep space where their maximum efficiency over chemical deep space stages can be realized.  <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

wick07 · Mar 27, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Wow, do you ... but I'd diversify my portfolio if I did. Posted by qso1</DIV> I agree across the board with the assessment of nuclear rockets.  If they are not reusable they are not feasible, too expensive and why waste all that nuclear fuel?  I think we can agree that for nuclear rockets to be used extensively the following criteria must be met:1) They are reusable.2) Nuclear contamination must be minimized [GCNR have an advantage here since in theory your working fluid (ie: H2) does not mix with your fuel (ie: Uranium Hexafluoride)] if you intend to use them in the atmosphere.3) Your gain in ISP/thrust must exceed you increased weight penalty.I think each of these can be met.  1 & 3 in the near term for extra-atmospheric use, and two in the longer term with the development of GCNR.  If you look at the link I posted earlier Pratt & Whitney already have a design that they would like to take to the prototype phase (all they need is lots of $$).  Of course a prototype is only a beginning, but this shows that this technology has evolved beyond the cool sci-fi only phase and is ready for more serious investment.  VASMR is in a similar place.  IHMO we may see either of these engines operational in our lifetimes. <div class="Discussion_UserSignature"> _______________________________ "If you are surrounded by those who constatly agree with you, then you're in an intellectual vacuum. If you feel like trying to make a difference, you have to BE different. How can you do that without interacting with those who are different from yourself?"- a_lost_packet_ </div>

Swampcat · Mar 27, 2008

I just have a few quibbles about some terminology..."Here think ISP or Initial Specific Impulse. A measure of a rockets propellant efficiency combined with engine design." -- qso1 My understanding is that ISP is another way of writing Isp and is an abbreviation for Specific Impulse. For more info see here."I thought, that oxidier [sic] together with hydrogen form propellant..." --mako71Oxygen and hydrogen are specific propellants, in and of themselves. Oxygen being an oxidizer and hydrogen being a fuel. There are, of course, other possible propellants, both fuels and oxidizers."Chemical rockets use binary propellant, because the chemical reaction between propellant components is the source of energy for throwing that propellant..." --mako71 Chemical rockets are not restricted to the use of two propellants. There are monopropellant motors as well as motors that use three propellants. Hydrazine can be used to generate thrust as can HTP and nitrous oxide. RATTWorks makes a tri-brid amateur rocket motor that uses nitrous oxide, alcohol and an ABS plastic fuel grain.I know these quibbles are somewhat OT, so pardon me for interjecting, but I just had to comment. <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" />Interesting discussion...carry on. <div class="Discussion_UserSignature"> ------------------------------------------------------------------- "I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."Thomas Jefferson </div>

qso1 · Mar 27, 2008

That clears it up for me. I pretty much agree with your assessment on criteria for nuclear rocket use. <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

qso1 · Mar 27, 2008

I just have a few quibbles about some terminology..."Here think ISP or Initial Specific Impulse. A measure of a rockets propellant efficiency combined with engine design." -- qso1 My understanding is that ISP is another way of writing Isp and is an abbreviation for Specific Impulse.I've heard it called initial specific impulse and specific impulse and your right about the proper way to write the acronym out. I thought, that oxidier [sic] together with hydrogen form propellant..." --mako71Oxygen and hydrogen are specific propellants, in and of themselves. Oxygen being an oxidizer and hydrogen being a fuel.In a chemical rocket yes, this is correct but as for propellants, that can refer to any propulsive agent such as the agents used to propel stuff out of containers such as bug repellants. In all the literature I've seen about nuclear thermal rockets. I've never seen reference to a separate oxidizer or liquid oxygen as part of the NERVA system as evidenced by schematics of the engine.Then considering chemical vs nuclear upper stages, if the nuke had to carry ox and fuel, the weight of the oxidizer would kill any chance of competing with a chemical upper stage unless the nuclear engine and structures could be built extremely lightweight.these quibbles are somewhat OT, so pardon me for interjecting, but I just had to comment. Interesting discussion...carry on. Posted by SwampcatThe quibbles are no problem, I like to be as accurate as a layman can be on this an every little bit helps.  <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

mako71 · Mar 27, 2008

About that oxidier thing... What I meant was a comment to saying "...With nuclear engine you save the mass of the oxidizer...", which I think is not correct. Lets assume, that both engines (chemical and nuclear) has same ISP. Then they would both need the same amount of propellant to go to orbit. In chemical LOX/LH2 rocket, that propellant would be LOX and LH2, in nuclear that would (probably) be only LH2. But anyways, in this situation:mass[LH2, nuclear] = mass[LH2, chem] + mass[LOX, chem] <div class="Discussion_UserSignature"> ________________ reaaliaika.net </div>

qso1 · Mar 27, 2008

Its a bit more complicated, take the shuttle external tank propellants for example. The oxidizer (LOX) weighs in at 1.3 million pounds while the fuel (LH2) weighs in at 226,000 lbs IIRC, and the LH2 tank is much larger than the Ox tank. The ox is much heavier and roughly 6 times heavier at that. There are variables affecting Isp such as engine design, propellant mixture ratio etc. Furthermore, oxidizer, as its name implies, is required for the rocket engine to burn fuel exoatmospherically.In a nuclear system such as NERVA. The propellant, be it hydrogen or whatever, will stick with hydrogen. The hydrogen is heated within the nuclear reactor itself then expelled through a rocket nozzle. The reactor in effect, plays the role of oxidizer in a nuclear system. Otherwise, the weight of LOX alone would make a nuclear upper stage thats equivalent to a chemical counterpart, so heavy...it would require much greater Isp to make up for the ox weight. Also keep in mind, this applies only to solid core thermal nukes for now.As it currently stands...if you took say, a Saturn third stage and built another third stage that was nuclear propelled. The nuke stage would have almost double the Isp as the chem stage and without the heavy ox. The problem as I understand it, is the nuclear rocket is, or would be a lot heavier than its chem counterpart. The nuke S-IVB would likely still outperform its chemical counterpart and with the advances in materials tech since the 1960s, it could probably be built lighter. But would it outperform it enough to justify the cost and environmental concerns?Is nuclear propulsion in our future...if were ever going to put humans on mars and go beyond, you bet it is. So certainly you are correct about the future of nuclear propulsion in our or someones future. Its probably a matter of time more than anything. And a matter of what type to develop.   <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

mako71 · Mar 27, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Its a bit more complicated, take the shuttle external tank propellants for example. The oxidizer (LOX) weighs in at 1.3 million pounds while the fuel (LH2) weighs in at 226,000 lbs IIRC, and the LH2 tank is much larger than the Ox tank. The ox is much heavier and roughly 6 times heavier at that.</DIV>Does that really matter? If you would have a shuttle with nuclear engine using LH2 as propellant, and with the same ISP and engine mass as the current shuttle, you would need 1.3 + 0.226 ~1.5 million pounds propellant (in this case, LH2). The only effect that LOX is denser than LH2 is that the 1.5 million pound external propellant tank would be larger than in chem shuttle, right?AFAIK, only the increasing ISP would make the propellant tank lighter. Replying to: <DIV CLASS='Discussion_PostQuote'>In a nuclear system such as NERVA. The propellant, be it hydrogen or whatever, will stick with hydrogen.</DIV>I once read why they planned to use hydrogen as propellant for nuclear engines, but I can't remember why. Was it that hydrogen give the best exhaust velocity and better ISP than heavier propellants like H2O?EDIT: BTW, nuclear engines could also be used like air-augmented rockets, that is, taking air in and heating it with nuclear power (nuclear-powered ramjet/ramrocket); that could be used to reduce some of the needed propellant... <div class="Discussion_UserSignature"> ________________ reaaliaika.net </div>

qso1 · Mar 27, 2008

If you had a nuclear shuttle. It would start off right off the bat 1.3 million lbs lighter at liftoff. The Isp would be 800 or so instead of the current 450 of the chemical powered shuttle. The LH2 part of the ET could go unchanged to continue to structurally and aerodynamically accomodate the orbiter and boosters. But theoretically, it could be shorter or as you mentioned, make up in part for the loss of the LOX weight by adding more LH2. The nuclear engines would weigh more than the SSMEs, but loosing the LOX would help make up that deficiency.But heres the problem. According to one article I saw in wiki, nuclear thermal engines are not powerful enough to lift themselves and payload from the ground which is why they are better suited as upper stages. I don't know why this couldn't be overcome but its probably because the designers were designing nuclear engines for human mars missions. Otherwise, if one wanted to use nuclear thermal rockets to get off the ground and had a justification, it could probably be done. Regardless of technical issues, one thing for certain about nuclear is its cost. And anything human spaceflight related is expensive which is why NASA is stuck in low orbit and with relying on chemical rockets.Hydrogen was used as propellant for NERVA engines because its light...offers the most bang for the chemical buck, and was readily available and generally stable. Fluorine has been considered for rocket fuel because when burned with LOX, Fluorine and LOX yeild a higher Isp than LH2 and LOX. Something like 500. I didn't ever see a published account of why its not used so I had to assume it was either unstable, unavailable in large quantities or both. <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

qso1 · Mar 27, 2008

http://www.fas.org/nuke/space/c02early.htmFrom the above link, I found another reason hydrogen is the ideal propellant for nuclear engines, I'll post the paragraph here:Hydrogen is an effective neutron shield, and thus hydrogen propellants, or hydrogenous materials, such as lithium hydride, are effective in slowing fast neutrons. High cross-section absorbers, such as boron, are included in shields to capture the resulting thermal neutrons. Shielding against gamma rays results from various types of interactions between the gamma ray photon and electrons, and thus depends on the density of electrons in the shield material. Heavy elements, such as lead, bismuth and tungsten, as well as iron and nickel, are effective gamma ray shields. <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

qso1 · Mar 27, 2008

I also found the passage below from the same link I previously posted."... barring entirely new discoveries in the field of nuclear energy, it is not likely that chemical propulsion will be replaced by an atomic power plant. In our proposed lunar trip, the landing on the moon's surface and the subsequent take-off require several hundred tons of thrust, and this involves the transfer of energy on such a scale that chemical propellants will prove to be superior. Nuclear rocket drives may some day be successful for flights between heavenly bodies for surveying and photographing purposes, but not when landings must be made. The weight alone of an atomic plan as we now conceive it would make the landing and take-off of huge rocket ships not only uneconomical but virtually impossible."   <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

mako71 · Mar 28, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Fluorine has been considered for rocket fuel because when burned with LOX, Fluorine and LOX yeild a higher Isp than LH2 and LOX. Something like 500. I didn't ever see a published account of why its not used so I had to assume it was either unstable, unavailable in large quantities or both. Posted by qso1</DIV>I think that one of the reasons for that is, that the end product (HF) is toxic acid... <div class="Discussion_UserSignature"> ________________ reaaliaika.net </div>

Swampcat · Mar 28, 2008

"Fluorine has been considered for rocket fuel because when burned with LOX, Fluorine and LOX yeild a higher Isp than LH2 and LOX." -- qso1Uh, fluorine is an oxidizer. It's not used because it is highly unstable and extremely toxic. <div class="Discussion_UserSignature"> ------------------------------------------------------------------- "I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."Thomas Jefferson </div>

wick07 · Mar 28, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>I also found the passage below from the same link I previously posted."... barring entirely new discoveries in the field of nuclear energy, it is not likely that chemical propulsion will be replaced by an atomic power plant. In our proposed lunar trip, the landing on the moon's surface and the subsequent take-off require several hundred tons of thrust, and this involves the transfer of energy on such a scale that chemical propellants will prove to be superior. Nuclear rocket drives may some day be successful for flights between heavenly bodies for surveying and photographing purposes, but not when landings must be made. The weight alone of an atomic plan as we now conceive it would make the landing and take-off of huge rocket ships not only uneconomical but virtually impossible."   Posted by qso1</DIV> This is like saying to Robert Goddard in 1930, "Unless we make some new discoveries about rocket design this thing is never going to be able to launch people into space!"  It may be technically true, but it fails to take into account the fact that the technology is in it's infancy.  The limiting factor in nuclear rockets is how high a a temperature the internal components can stand.  The limiting factor of chemical rockets is how much energy you can get out of the chemical reaction.  The first is a wide open field with many chances to improve in material design and engineering.  The second is a limit that we are already pushing the upper boundaries of.  An increase in ISP of 450 to 500 is only about 10%.  An increase from and ISP of 800 to 3000 is almost four-fold.By the way, I wanted to take a moment to mention VASMR, which in my rabid defending of nuclear I have neglected.  VASMR also shows incredible promise and is another technology where we have barely scratched the surface.  I predict great things from it.<img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-cool.gif" border="0" alt="Cool" title="Cool" /> <div class="Discussion_UserSignature"> _______________________________ "If you are surrounded by those who constatly agree with you, then you're in an intellectual vacuum. If you feel like trying to make a difference, you have to BE different. How can you do that without interacting with those who are different from yourself?"- a_lost_packet_ </div>

qso1 · Mar 28, 2008

Uh, fluorine is an oxidizer. It's not used because it is highly unstable and extremely toxic. Posted by SwampcatMy bad this time, thanks for pointing out the discrepancy. I did recall it being unstable but didn't know it was toxic on top of that.  <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

qso1 · Mar 28, 2008

This is like saying to Robert Goddard in 1930, "Unless we make some new discoveries about rocket design this thing is never going to be able to launch people into space!"  It may be technically true, but it fails to take into account the fact that the technology is in it's infancy. Posted by wick07True. Unfortnately the technology is stillborn for now. We are no further along in advancing nuclear thermal rocket technology beyond ground tests than we were in 1972 when the program was canned. Goddard to the moon was 40 years (1929-1969). The moon and nuclear propulsion testing goin on then was a year short of fourty years ago. Unlike Goddards test rockets that led to the Saturn V and shuttle, nuclear propulsion is still in labs at best.But, like you I do think it will be the future for space travel especially deep space. The question is, how far into the future and will America pioneer it?  <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

wick07 · Mar 28, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>This is like saying to Robert Goddard in 1930, "Unless we make some new discoveries about rocket design this thing is never going to be able to launch people into space!"  It may be technically true, but it fails to take into account the fact that the technology is in it's infancy. Posted by wick07True. Unfortnately the technology is stillborn for now. We are no further along in advancing nuclear thermal rocket technology beyond ground tests than we were in 1972 when the program was canned. Goddard to the moon was 40 years (1929-1969). The moon and nuclear propulsion testing goin on then was a year short of fourty years ago. Unlike Goddards test rockets that led to the Saturn V and shuttle, nuclear propulsion is still in labs at best.But, like you I do think it will be the future for space travel especially deep space. The question is, how far into the future and will America pioneer it?  Posted by qso1</DIV>I don't know about you, but whenever I see something about VASMR I always think "Wow, that seems like a good way to start nuclear fusion!"  If we used a combination of deuterium and tritium and used the VASMR engine to reach Lawson's Criteria perhaps we could build a nuclear fusion engine.  This would seem to me to be a simpler was to use fusion since it only needs to be semi-controlled and the energy could be harnessed directly (as exhaust).  If we wanted a powerful engine, there's the ticket! <div class="Discussion_UserSignature"> _______________________________ "If you are surrounded by those who constatly agree with you, then you're in an intellectual vacuum. If you feel like trying to make a difference, you have to BE different. How can you do that without interacting with those who are different from yourself?"- a_lost_packet_ </div>

qso1 · Mar 28, 2008

VASIMR is not so far from being an all out fusion rocket and fusion rockets have been proposed. I recall one concept for a laser fusion rocket where a laser is fired into a pellet of deuterium to initiate fusion.A VASIMR based propulsion system is definetily the way to go IMO as laser or other fusion concepts still need work on reducing the mass of the reactor.  <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

neilsox · Apr 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>I think Nuclear Rocket engines are the future.  We have pretty much reached our limit with chemical engines.  Yeah, we can squeeze a bit more juice out of them, but if we really want to explore space we need to improve our engine by orders of magnitude------------------------------------------------------------------------------------------ Read the post above!! The boosters are not that much smaller using nuclear .And really is no good for doing earth orbits.Going to the moon or mars is where the nuclear rocket comes in!! But its does not seem to be that powerful.Wow the Ariane V sure looks cool!! They seem to have a potential in the UK for man space in the UK , using the Ariane V.But problem seems to be the government not interested. Posted by nec208</DIV> Fission rockets may be great, but the development on Earth's surface means millions of people die a bit younger due to poluting our biosphere with radioactive waste. With adequit off Earth bases, we can develop fission rockets endangering only the base personel instead of up to 6 billion Earthlings.   Neil

neilsox · Apr 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>"Fluorine has been considered for rocket fuel because when burned with LOX, Fluorine and LOX yeild a higher Isp than LH2 and LOX." -- qso1Uh, fluorine is an oxidizer. It's not used because it is highly unstable and extremely toxic. Posted by Swampcat</DIV> Liquid fluorine = stable, but very toxic and corrosive could replace LOX in many engines with some major redesign. The HF exhaust would corrode the engine nozzles and most everything on the launch pad including the humans. A small thrust improvement would occur. Florine is less available and more costly than LOX but cost is a minor problem compared to corrosion.  Neil

Swampcat · Apr 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Liquid fluorine = stable, but very toxic and corrosive could replace LOX in many engines with some major redesign. The HF exhaust would corrode the engine nozzles and most everything on the launch pad including the humans. A small thrust improvement would occur. Florine is less available and more costly than LOX but cost is a minor problem compared to corrosion.  Neil Posted by neilsox</DIV> OK, maybe my use of the word "unstable" wasn't technically correct. What I meant was that it is so reactive with just about anything that it doesn't want to stay in its "stable" form. <div class="Discussion_UserSignature"> ------------------------------------------------------------------- "I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."Thomas Jefferson </div>

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