If Nixon had not cancelled NERVA,

[qso1]

I agree with that. But I just looked and saw that we have close to a whole page on stuff not really related to the topic at hand. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>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.</em></p> </div>

 

[scottb50]

Perhaps thats because it wouldn't have worked then or now. <div class="Discussion_UserSignature"> </div>

 

[qso1]

NERVA had undergone actual testing including engine firings and showed no serious technical hurdles. Its cancellation was the direct result of the politics of anti human spaceflight criticisms regarding how the money could better be spent. After Apollo, nobody outside the space community wanted a commitment to an even larger program than Apollo.<br /><br />NERVA as part of the planned mars program was part of an expensive program estimated at that time to be around $100 billion dollars. NERVA had not reached full scale engine testing (200K thrust) and its possible technical issues could have cropped up had those tests been done. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>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.</em></p> </div>

 

[vulture2]

Nerva had sinoificant technical hurdles in that the ground test version, Kiwi, had a tendency to lose bits of its core out the exhaust. More to the point, high delta-V missions like Jupiter Icy Moons Explorer get better ISP from ion propulsion but require a reactor to provide the power. Unfortunately JIMO has been cancelled due to cost growth; however a flyable reactor is still needed if we are ever to fully explore the outer planets, or send people to Mars in a reasonable time. <br />

 

[gunsandrockets]

<NERVA had not reached full scale engine testing (200K thrust) and its possible technical issues could have cropped up had those tests been done.><br /><br />I recommend the book, "to the end of the solar system: the story of the nuclear rocket". It goes into exhausting detail of every aspect of the nuclear rocket project and the testing done, plus covering all of the insider Washington politics which shaped the program from the beginning until the end.<br /><br />The biggest engine-reactor, I believe called Phobos II, WAS test fired during the NERVA program. Phobos II was supposed to lead to the 1/4 million pound thrust engine sometimes referred to as the NERVA II engine. The reactor was supposed to function at a power output of 5,000 megawatts of heat! The testing of Phobos II was shut down before a fully successful test run was completed, in part because of the outstanding and ever increasing testing success of the lower powered engine-reactors.<br /><br />The lower powered engine was the so-called NERVA I engine, which was going to only be a 75,000 lbf thrust engine and only generate 1,500 megawatts of heat. I believe the cutting edge liquid-hydrogen turbo-pump for the NERVA I lived on as the turbopump for the J-2 engine! Testing of the smaller nuclear engine showed continuous thrust for an operating period exceeding 1 hour and an expected lifetime of 10 hours of thrust. Such outstanding success even opened up the possibility of conducting multiple missions with the same engine, opening up a path to a reusable space-tug.<br /><br />With such outstanding endurance, the NERVA I engine could perform the jobs that the NERVA II was originally designed for, such as the main propulsion element of a manned mission to Mars. When the nuclear project began there were many ideas of how a nuclear engine might be employed, and how well it might work. As the testing program proceeded, smaller and smaller nuclear engines were considered adequate for the anticipated miss

 

[gunsandrockets]

<Nerva had sinoificant technical hurdles in that the ground test version, Kiwi, had a tendency to lose bits of its core out the exhaust.><br /><br />The 1,150 megawatt power Phobos I demonstrated continuous full-power output exceeding 1 hour length and at a temperature exceeding 2,000 degrees Celsius. That is a completely successful test result. Such an engine is adequate for a manned mission to Mars and would have provided an engine with an ISP exceeding 825 seconds.<br /><br />You may be confusing core erosion with core disassembly. An early test bed reactor with a different core design fell apart during testing and ejected whole segments of the core out the nozzle. But even that catastrophic failure did not lead to a loss of engine control or the destruction of the engine. Nuclear engines don't seem to have the hard-start explosive problems that chemical engines can have. A new core design was implemented after the failure of the first core design, and it went on to extremely long duration tests. <br /><br />Now the new core design did undergo core erosion, a problem which the testers were always coming up with new ways to reduce. But the problem of core erosion only relates to total engine endurance. Towards the end of the program engine endurance was over 10 hours at full power operation!<br /><br />By the end of the program, it was expected that nuclear engines were only going to be operated in space, not fired suborbitally or within the Earth's atmosphere. The small amount of erosion ejected during space operation wouldn't be a problem.

 

[gunsandrockets]

<Perhaps thats because it wouldn't have worked then or now. ><br /><br />Except that it did work then and it could work now!

 

[scottb50]

I've never said there was a problem getting a reactor to operate at the levels required. What I have said is it has a lot of baggage that makes one wonder if it could meet the needs.<br /><br />To begin with you would need to run at high power to get the thrust needed to establish an orbit to intersect Mars orbit, next you need to provide power en route, ion engines might help, but you still have to slow down at the other end.<br /><br /> At Mars you would need high reactor output to enter orbit then a return to lower power. The problem is cooling. <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

A working nuclear engine design was fully tested. The only thing they didn't do back then is build the flight hardware.

 

[qso1]

The NERVA was tested to 50,000 lbs thrust IIRC and the target was a 200,000 lb thrust engine. Cooling was to have been provided by the LH2 propellant supply for the engine. If LH2 can't cool it down, I don't know what can. However, there were technical issues as you mentioned. I suspect they would have overcome them had development not been cancelled. At the time of cancellation, NERVA still had about five years or so to test fire full thrust engines. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>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.</em></p> </div>

 

[gunsandrockets]

What is your source?