Nuclear Thermal Propulsion

[crix]

"hippy moon base" omg, haha, that's comedy gold!

 

[lampblack]

<font color="yellow">"hippy moon base" omg, haha, that's comedy gold!</font><br /><br />I had sort of wondered where all the hippies had gone. <div class="Discussion_UserSignature"> <font color="#0000ff"><strong>Just tell the truth and let the chips fall...</strong></font> </div>

 

[JonClarke]

Calli:<br /><br />Thanks for splitting this off after the original thread was diverted into yet another NTR thread.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

<i>First off the Kiwi engine destroyed in the 1965 experiment was 4 times more powerful than the NTR engines being considered today. Secondly the reactor was rigged to blow by modifying the control drums to move 100 times the normal rate so as to overload the reactor. Thirdly the experiment was not a test of possible engine failure or of coolant loss but an engine deliberately rigged to overload.</i><br /><br />No NTRs are formally being considered today. The most recent proposal in the US literature I am aware of was the adaptation by Borowski et al. in numerous publications of a Russian design. This had a conceptual rating of 335 mWt. As you are doubtless aware there were many different Kiwis, these varied in power rating between 70 and 990 mWt and those broadly equivalent to the Borowski design.<br /><br />Again, as you are doubtless aware, there are many different possible failures. Control system malfunction resulting in excessive power output is one (as in kiwi-TNT). Coolant/propellant loss is another. In each case the final consequences will be the same, destruction of the reactor core.<br /><br /><i>And despite all this just how bad was the Kiwi "explosion"? About equal to 150 pounds of TNT. And how bad was the contamination? From the report..."Radiation effects from the cloud passage were less than predicted in the pretest safety evaluation report. The maximum off-site, integrated, whole-body exposure was 5.7 mrad about 15 miles from the test point."</i><br /><br />You are missing the point. The problem is not the force of the "explosion", it is the amount radiation released and the contamination that results. The radiation intensity from Kiwi TNT would have resulted in 100% fatalities out to 90 m from the reactor and lessening fatalities out to 228 m.<br /><br />Any release of radioactivity into the environment is a notifiable event that can result in legal action, irrespective of whether or not people are actual injured or even exposed. Believe me, having s <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

<i>The people doing the testing during NERVA were not idiots. Most of them worked for Los Alamos or Lawrence Livermore and developed scientific modeling to aid development as much as possible. It's one of the reasons the speed of nuclear rocket development exceeded all expectations and estimates.</i><br /><br />"Idiot" is your word, not mine. I have never impugned the intelligence of those involved in this work (wisdom is a very different thing to intelligence). The program exceeded estimates and expectations except for the minor detail that, after an expenditure of US$1.4 billion in 1973 terms (more than US$7 billion today) there still was not a flight ready engine. Likewise for the DoD program whose costs are still classified.<br /><br /><i>It isn't necessary to build an all-up complete engine and fly it in space to know whether a new design fuel element can resist higher reactor temperatures and propellant erosion. That was the reason for the 'furnace reactor', for testing advanced fuel element design.</i><br /><br />It is an important part of the development process but it is still not the equivalent of a all up test.<br /><br /><i>Existing fuel element design showed performance high enough for 900 ISP. That is good enough to rebut the notion that 950 ISP is some ridiculous pie in the sky figure.</i><br /><br />NERVA never reached 900, although it might have done <i>in vaco</i>. I never said that 950 is pie in the sky (once again you are putting words in my mouth) but it is a number that has yet to be achieved in practice.<br /><br /><i>If an NTR uses ammonia for propellant, the challenges for successful restart after years in space are less than for any chemical engine including those using hypergolic propellant. An NTR can control it's thermal environment, unlike a cold chemical engine, and ammonia is much more easy to store than any oxidizer/fuel combination of any liquid chemical engine.</i><br /><br />Ammonia is an interesting propellant because it is so storable. How <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

This is the first time I have been called a hippy - and i was round in the hippy era too!<br /><br />In sifting the wheat from the granola, your post seems to fall into three assertions.<br /><br />1. <i>And how far away from that big fusion engine in the sky can the 'highly reliable' and eco-friendly solar panels stray before going dead?</i><br /><br />The issue in question is a human Mars mission, not how far from the sun solar power is viable. Solar irradiance in Mars orbit is 600 W/m2. Assuming current efficiencies of 20% that is 120 W/m2. A 4-person Mars transfer vehicle (MTV) would need about 20 kW to run onboard systems. In Mars orbit this could be supplied with a 20% margin by a 200 m2 array, a pair of panels each 20 X 5 m. This is very achievable and smaller than arrays that have already been flown in space. <br /><br />2. <i>Heaven help the astronauts in the solar-powered Mars habitat designed by granola-munching hippies when the Martian weather goes bad and those global dust storms kick up?</i><br /><br />My comment was originally specifically referring to the journey to and from Mars in an MTV. Mars surface operations are somewhat different and not relevant to the issue of NTR which is the point of this thread. But, since you asked, and it is of marginal interest, a solar powered Mars station is feasible.<br /><br />First consider normal operating conditions. Twelve hour average solar irradiance at latitudes of 20 degrees is 300 W/m2. Assuming a 4 person Mars habitat (MH) can run of 20 kW like the MTV and cells of the same efficiency, you have 60 W/m2 and would need 400 m2 of array to supply the power with the same 20% margin. This could be laid out as a 200 X 2 m mat, covering in a square of 20 m on a side, smaller than my suburban block. <br /><br />During global dust storms irradiance falls to 90 W/m2 or 18 W/m2 of delivered power. Global dust storms (which are not annual occurrences) last up to 100 days. In this case the hab would have to go into an lower <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

"NS, we need nuclear power in space."<br /><br />The issue is not whether or not we should use nuclear power in space, but for which applications is it most suited.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

Many people on these boards have advocated a resumption of development of NTRs, especially for Mars missions. Some of these discussions have gone round in circles. So I would like to propose the following 10 questions that should be answered by NTR advocates to provide a baseline comparison of the merits on NTR and non-NTR options for missions to mars and elsewhere. Each question should be addressed separately in subthreads with their own heading to minimise post length and confusion.<br /><br />So, defining an NTR as a solid reactor core propulsion system equivalent to NERVA and the RD-0410:<br /><br />1. What fission product emissions levels from an NTR will be acceptable?<br /><br />2. What level of reliability will be acceptable for a NTR?<br /><br />3 . What is the maximum credible accident (MCA) for an NTR?<br /><br />4. How can containment during a MCA be achieved?<br /><br />5. How is safe disposal of spent NTR stages to be achieved?<br /><br />6. What actual performance advantage (e.g. mass ratio of EDS for a 6-month cruise to Mars) would such a NTR achieve over a baseline chemical stage (payload-EDS mass ratio of 0.6)?<br /><br />7. How can a flight-ready NTR be safely developed on earth?<br /><br />8.. What infrastructure and skills base development will be needed for (5)?<br /><br />9. How long would it take to develop an NTR that meets the specified emission, containment, and reliability standards?<br /><br />10. How much would such a development program be likely to cost (nearest 10 billion)? <br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[j05h]

I commend Jon Clarke for some level-headed suggestions for Nuclear Rockets. The NTR "debate" usually breaks down into 2 camps, roughly Fans and Environmentalists. Jon's suggestions are practical questions that need to be answered to know if this kind of rocketry is even possible in practice. The ground test articles proved it is technically possible, the closest in-space "nuclear" vehicles I know of are old Soviet radar sats that spewed radioactive sodium coolants at end-of-life. So, the on-orbit record for handling reactors (power or NTR) is less than stellar. Disposal and Earth-side infrastructure would likely be the factors that keep NTR from achieving production. <br /><br />And, for the original thread, ARES 5 heavy-lift opens up all sorts of possible missions, as any HLV would. The important question for HLV on-orbit assembly is whether private interests will have access to ARES 5? If not, it doesn't matter. NASA knows roughly how much money they are going to receive and have planned accordingly in ESAS. What if Exxon decides it needs to build a 600ton mining platform for Apophis or Phobos, will they have access to ARES vehicles? Will the HLV be commercially available or locked in as a NASA-only vehicle? Instead of talking about ARES 5 missions, we should be asking what the production capacity of the ARES 5 core assembly line will be?<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[Swampcat]

<font color="yellow">"Will the HLV be commercially available or locked in as a NASA-only vehicle?"</font><br /><br />This is an interesting point of view. It gets to the question of what NASA's role is in the whole picture of the exploitation of space and its resources.<br /><br />If indeed the Ares 5 becomes commercially available, then it's a moot point, but what are the chances of that? Was there ever any real possibility that the Saturn 5 or STS would be made available to private interests? Hardly, though I understand there was some talk about that in regards to STS. Of course, it didn't happen.<br /><br />Is it NASA's job to assist in the building up of commercial interests? That's a tough question, but one that, in the past, has generally been answered in the negative. Why that was so is somewhat of a mystery to me as it would fit nicely within the phrase "promote the general welfare" which is in the Preamble of the US Constitution. It's been refreshing to see some of the changes in NASA's attitude toward space commercialization that have been seen recently.<br /><br />In this regard, the use of commercially available LVs (Delta, Atlas, Falcon, etc.), particularly for the Ares 1 function, would make a lot of sense. In addition, if, instead of a NASA contract for a purpose-built HLV, NASA were to say that they needed <i>x</i> amount of lift capability by a certain date and would contract with whomever could provide that capability, how would that work? Could it guarantee the availability of that capability to NASA's timeline? Could some commercial interest then afford to purchase such lift capability as well?<br /><br />I have my doubts, but it would be interesting to find out.<br /><br />I realized after I posted this that it was OT...sorry 'bout that. <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"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."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[nacnud]

There were commcerial launchest on the STS before Challanger. I see no reason why there can't be a commercial launch on an Ares V, so long as there is sufficent capacity for spare/commercial vehicels.

 

[Boris_Badenov]

Those are the best questions I have ever seen asked on these boards in regards to NTR’s. <br /> My only response is the same one I always use in this situation; Until we start building & using NTR’s, we will never have the chance to find out how good they can get.<br /> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[j05h]

>> "Will the HLV be commercially available or locked in as a NASA-only vehicle?"<br /> /> This is an interesting point of view. It gets to the question of what NASA's role is in the whole picture of the exploitation of space and its resources. <br /><br />Thank you. For myself, commercial access to true heavy lift is the only thing that matters about the VSE. <br /><br /> /> Is it NASA's job to assist in the building up of commercial interests? That's a tough question, but one that, in the past, has generally been answered in the negative.<br /><br />Except that it is in the NASA charter (sect.5, IIRC) that the Agency is supposed to support commercial development. I read that as "technical support and spin-offs" not "corporate welfare".<br /><br />I don't think that private companies would build an HLV if NASA promised a market, I tend to think they would settle on a dirt-cheap 20-60ton BDB launcher or similiar. I do think that a promise to pay commercial rates for ISS cargo is a great idea. Commercial access to HLV would allow significant changes to space-based engineering, design and expedition profiles. It would allow the rapid settling of the inner solar system. It isn't needed, though, and NASA has made no moves to indicate it will be available. <br /><br />Like I said, things will change once companies like Exxon start seeing that money can be made upstairs. I am still holding my breath for a SeaDragon derivative.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>There were commcerial launchest on the STS before Challanger. I see no reason why there can't be a commercial launch on an Ares V, so long as there is sufficent capacity for spare/commercial vehicels.<p><hr /></p></p></blockquote><br /><br />It was kind of an oddity, though. NASA is prohibited by law (as are all US government organizations) from directly competing with commercial activities. In the early 80s, there weren't many options for launching commerical satellites, and the commercial providers could not meet demand. Therefore, Shuttles were permitted to carry commercial satellites in their spare upload capacity, or to perform missions involving commsats which were simply not possible with any other hardware. But the situation has changed considerably since then, and a commsat would need a very persuasive argument before NASA could be allowed to carry it. (They do carry commercial payloads; small experiments aboard the Space Shuttle and the ISS. But again, these are going into a currently-unique environment. There is no commercial provider. Bigelow may change that in the not-too-distant future, but for now, NASA is the only provider of this sort of test environment.)<br /><br />So, what does this mean for Ares V? Commercial launches will probably be permitted until such time as the commercial market starts providing private launches of similar capacity. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>