Talk:NERVA

Exhaust velocity contradiction
From a NASA website article... [NERVA]"...demonstrated an effective exhaust velocity of 24,450 ft/sec, far more than any chemically-fueled rocket could achieve." This is in complete contradiction to this article. http://history.nasa.gov/SP-4221/ch3.htm


 * As I understand it, exhaust velocity != thrust. Thrust is baiscally mass / time * velocity of the exhaust. That would give me the idea, that the throughput of NERVA was not big enough. Regards -- M

Exhaust velocity and thrust have nothing to do with one another. Exhaust velocity does, however, scale with efficiency. Nuclear rockets are far more efficient than chemical rockets; they get more thrust per pound of propellant ejected by achieving much higher exhaust velocities. Check out the Wikipedia page on specific impulse.

"Throughput" is not a term seen in rocket circles, but you might be referring to "thrust" or "total impulse". In theoretical terms, a nuclear rocket may be built to any size; in practical terms, NERVA was actually scaled down by a factor of 4 as its efficiency and reliability increased. Need to go faster (Mars)? Run a smaller NERVA engine longer.

Also in practical terms, many people feel that a chemical rocket visit to Mars or even logistical support by chemical rockets of an extended lunar mission are (again, practically speaking) unfeasible. Chemical rockets have to grow so big that they become both unwieldy and unfundable. As chemical mission durations increase, so must radiation shielding and supplies, but then the vehicle size again increases, etc. etc. The chemical bond doesn't have enough energy to even logistically support an extended lunar mission, much less anything beyond. Voronwae (talk) 02:14, 19 March 2010 (UTC)

Kiwi technology?
From the article:


 * "The NERVA rocket engine was based on Kiwi nuclear reactor technology."

What does this mean? Was Kiwi the name of a project? Or is this referring to New Zealanders? Cite, please? -- Karada 16:10, 30 June 2007 (UTC)
 * From the Nuclear thermal rocket Article "The reactor was not intended for flight, hence the naming of the rocket after a flightless bird". It has nothing to do with the slang term for New Zealanders.  I have re-inserted this back into the NERVA article with the clarification. -- Roidroid 07:03, 4 October 2007 (UTC)

Baxters Voyage - Apollo/NERVA & Apollo 6
I've just finished reading Stephen Baxters Voyage and would like to throw something into the mix here. What no-one seems to have noticed (or at least commented on) is that the Apollo-N mission event sequence is taken straight from Apollo 6. Not sure where he got his NERVA stage design from though. He describes a third stage with gimballed(sic) engines, the designs I have seen for Saturn NERVA stages however all use vernier engines for trajectory control. Graham1973 (talk) 16:26, 3 September 2008 (UTC)

At the time Baxter wrote the novel I'm guessing good sources on NERVA were not available. Voronwae (talk) 02:01, 19 March 2010 (UTC)

Potential sources/references
— jhf (talk) 23:40, 15 April 2009 (UTC)
 * NUCLEAR ROCKETS FOR SPACEFLIGHT — page by page PDFs at flightglobal.com, from 1967
 * pt. II of above
 * An Historical Perspective of the NERVA Nuclear Rocket Engine Technology Program, PDF, 1991, 1.1MB.
 * NUCLEAR ROCKETS BASED ON GRAPHITE REACTOR TECHNOLOGY, PDF, 1963, 93.4MB.

...also proposed a Manned Mars Mission using...
Should "Manned Mars Mission" be capitalized? —Preceding unsigned comment added by 205.206.130.52 (talk) 07:13, 29 October 2009 (UTC)

40%?
Where does the 40% figure come from? Is there a reference? vttoth (talk) 12:47, 16 November 2009 (UTC)
 * Moreover, the whole paragraph is strange. What does mean «very» expensive ? What was the information delivered to the public and its reaction ? What theorical thrust (the designed thrust was 330 kN and was obtained) ?
 * This addition from IP needs to be sourced or removed. Duc ky sm ok ton  blabla 22:20, 18 November 2009 (UTC)

Bad specifications from Astronautix
At some point I'm going to replace the erroneous specs at the page bottom from Astronautix, as soon as I have proper figures to replace them. I do know that according to the contractor report I cite throughout the page (written by Ben Finger) the stated thrust for NERVA was 75,000 pounds. I guess it's possible that efficiency increased and thrust went way, way up; I'll check that out, too. Voronwae (talk) 05:28, 19 March 2010 (UTC)

NERVA-like nuclear rocket on Discovery in 2001: A Space Odyssey
Didn't the Discovery spacecraft use nuclear thermal rocket propulsion? Should it be added to the list of fictional references in this article? Or is this list limited to direct fictional references to the NERVA engine as developed? Karn (talk) 17:55, 19 May 2010 (UTC)
 * (from memory) I remember that in 2001, the propulsion system is a nuclear fission - hydrogen propellant engine, and in 2010, Clarke corrected it to nuclear fission - ammonia (or methane ?) propellant so that the propellant supply could have survived the long interval between the missions.
 * But there is no details about how the heat transfer is done, it could be a NERVA solid graphite core or any other variant such as cermet, wire core, tungsten-water moderation, particle bed ... etc
 * So, any reference to 2001 Discovery should be in the nuclear thermal rocket article (BTW, many informations from the sections Progams & Test firings of this article should be moved in the NERVA article) Duc ky sm ok ton  blabla 10:23, 20 May 2010 (UTC)
 * According to the article Discovery One, the engine is a « Cavradyne » gaseous core engine, thus not a NTR engine. Duc ky sm ok ton  blabla 11:06, 20 May 2010 (UTC)

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Availability of hydrogen
The article says:


 * Hydrogen was theoretically the best possible propellant, but in the 1950s it was expensive, and available only in small quantities.[17]

This is sourced, but is it really correct? It sounds surprising to me. Large quantities of hydrogen had been produced decades earlier for airships, for example. 2A00:23C5:4B91:AB00:7CAF:AD1C:FAC6:A702 (talk) 19:08, 22 July 2019 (UTC)
 * Yes and no. The text has been corrected to "liquid hydrogen", which was only available in litre quantities in the 1950s. Thanks to Projects NERVA and Apollo, this bchanged dramatically in the 1960s.  Hawkeye7   (discuss)  20:42, 22 July 2019 (UTC)
 * Aha, I see, that makes much more sense now. Thanks for you reply. 2A00:23C5:4B91:AB00:7CAF:AD1C:FAC6:A702 (talk) 22:33, 22 July 2019 (UTC)
 * Thanks for picking that up.  Hawkeye7   (discuss)  22:43, 22 July 2019 (UTC)

Incorrect power rating?
The article states: “By 1955, it had settled on a 1,500 MW design called Old Black Joe. In 1956, this became the basis of 2,700 MW design intended to be the upper stage of an ICBM.”

These MW figures look high to me. Asubmarine reactor may be 150 MW. A commercial nuclear reactor might be as big as 1,000 MW. —40.142.140.74 (talk) 23:52, 12 August 2019 (UTC)


 * @40.142.140.74 yet, KIWI-B for NERVA was already at "above 1000 MW", so those figures are probably correct. running a steam plant based on a nuclear reactor is very different from running a rocket exhaust, none the least in the temperatures that are "allowed". 46.15.193.159 (talk) 21:53, 25 March 2024 (UTC)

Feedback
Hello. I enjoyed reading this article, but I feel there is a small gap: If NEVA was "flight-certified" and "the engine was deemed ready for integration into a spacecraft", how come in May 2019, $125 million were authorized to rediscover the wheel? It does not say it will continue the project, so that implies the start of a new [unrelated] project. Is this correct? Also, any indication that such engine is being considered for the Deep Space Transport (Orion + propelled Habitat)? Thanks Rowan Forest (talk) 23:07, 14 August 2019 (UTC)


 * I think they are improving the wheel rather than redeveloping it. According to a recent article, they want to continue the development work that Project Rover did on materials with new "cermet" (ceramic metallic) fuel rods, and they want to study options for liquid hydrogen storage employing new insulating materials developed since the 1970s. I suspect that most of the money will go on construction of new test facilities so the new engine can be ground tested without releasing radioactive fission products.  Hawkeye7   (discuss)  00:21, 15 August 2019 (UTC)
 * OK. Then I think you can add something to the effect that it is a continuation of the development/technology or so. Thanks.  The article flows well, considering it is a complex topic. Rowan Forest (talk) 13:58, 15 August 2019 (UTC)

Strange dollar sign
I have noticed this sentence in the NERVA NRX section ".. resulting in about $2.20 of reactivity lost, the engine could still have been restarted, but the engineers wanted to examine the core." Should this be % ?
 * No, reactivity is measured in dollars and cents. See Dollar (reactivity). I have added a duplicate link, although it is already linked above.  Hawkeye7   (discuss)  20:56, 18 August 2019 (UTC)

(I would like to congratulate all the editors who have written this  wonderful article on an amazing piece of technology. I can remember reading about Nerva in my "Peter Farley's Space Annual" in the early 1970s, so  this article really takes me back) KreyszigB (talk) 18:28, 18 August 2019 (UTC)
 * Nearly all of what you see was written by me. If your interested in the subject, I recommend Dewar, James (2007), To The End of the Solar System: The Story Of The Nuclear Rocket. He wrote his PhD on the nuclear rocket.  Hawkeye7   (discuss)  20:56, 18 August 2019 (UTC)

A source of confusion for readers: There are two Andersons
Senator Clinton P. Anderson and Lieutenant Colonel G. M. Anderson are both shortened to "Anderson" multiple times during the text, and it may not consistently be obvious which of them is intended. In my opinion, some clarification is needed. Perhaps including titles in the shorthands. "Senator Anderson" and "Chairman Anderson"? Elias (talk) 10:33, 8 October 2021 (UTC)


 * The colonel is mentioned only once. Added some disambiguation. Hawkeye7   (discuss)  18:51, 8 October 2021 (UTC)

Semi-protected edit request on 28 September 2023
Italic text 117.20.116.114 (talk) 06:20, 28 September 2023 (UTC)
 * Red question icon with gradient background.svg Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. NotAGenious (talk) 13:36, 28 September 2023 (UTC)

An atomic make-over
To be clear, why is there no mention of nuclear rockets in relation to 'Atoms for Peace' and other attempts at giving atomic power a public relations make-over? Also, given how US space rockets at the time had a nasty habit of blowing up - why is there no mention about the wisdom of attempting to place nuclear materials in space? — Preceding unsigned comment added by 2.27.2.5 (talk) 08:46, 28 September 2023 (UTC)

Semi-protected edit request on 28 September 2023 (2)
{{subst:trim|1=

nuh uh 193.40.227.94 (talk) 11:39, 28 September 2023 (UTC)
 * Red question icon with gradient background.svg Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. NotAGenious (talk) 13:36, 28 September 2023 (UTC)

Radiation emissions discussion
I assume the NERVA isn't radiation free. Shouldn't a section be added that discusses radiation emissions in the exhaust and any radiation hazards presented to the payloads being propelled? P Todd (talk) 15:16, 28 September 2023 (UTC)


 * I have added a paragraph on the radiation shield. The exhaust was of less concern since irradiation of hydrogen only produces deuterium and tritium. Hawkeye7   (discuss)  21:10, 28 September 2023 (UTC)

Needs much more coverage on environmental and health hazards
In addition to the call for a Radiation emissions discussion, the article needs discussion of environmental and health hazards, including the possibility of an unplanned re-entry or explosion of the launch vehicle causing a catastrophe; and what was the impact on workers and the locations of manufacture and testing; the article reads like typical pro-science rah rah; discussion of these and other risks should be prominent, not buried at the end. Skydog0x (talk) 18:51, 28 September 2023 (UTC)


 * This is discussed in the fifth paragraph of the Towards Reactor In-Flight Tests section. Hawkeye7   (discuss)  19:23, 28 September 2023 (UTC)

Comparisons
A fine piece as usual, but what I don't grasp is context. If the engine was done, how did it compare to contemporary engines, capability and costwise? How about to today's? That kind of context would make it easier to understand if canceling it was prudent or foolish.

This scholarship may not exist. I know I grew up assuming that nuclear engines were a dead end. But if they were not, it'd be nice to know what they could do relative to what we had.--Neopeius (talk) 20:41, 1 October 2023 (UTC)