NASA eyes nuclear-powered rocket

nirgal · 2003-01-24 17:31:32

The advantage of an NTR is that it doesn't *need* an oxidizer to achieve high exhaust velocities. The hydrogen is heated by the nuclear reactor and then accelerated on its way through the engine nozzel. The only limiting factor to the temperatures/exhaust velocities which can be achieved are the temperatures the materials of which the engine is made can endure without melting.

Mark S · 2003-01-24 18:08:33

Actually, in response to Rob S, the White House opposed the Pluto-Kuiper express because it didn't use advanced propulsion. Sean O" Keefe had gone on the record saying that the Pluto mission should be delayed until an RTG-powered ion thruster was ready. Such an engine would enable a Pluto Orbiter. The current mission will use chemical propulsion (although an RTG will provide power) and make a simple flyby of Pluto.

The nuclear propulsion team at NASA-Glenn Research Center has examined LOX-augmentation of nuclear-thermal rockets to boost their thrust. LOX would be injected into an afterburner section of the nozzle, increasing the thrust by interacting with the heated hydrogen. It's been called a "reverse scramjet" because the cobustion would take place in a supersonic flow.

Nirgal82 · 2003-01-24 22:17:26

The only limiting factor to the temperatures/exhaust velocities which can be achieved are the temperatures the materials of which the engine is made can endure without melting.

Well I remember that in the engines that powered the Saturn V's first stage (and I think the subsequent stages as well, and the shuttles main eniges too i believe) ran the fuel first through tubes around the engine bells to keep them cool enough to stay solid, I read that the engines actually burned hotter than the melting point of the materials used to build them, and that the fuel-as-coolant method was neccesary.

-Matt

Nirgal82 · 2003-01-24 22:23:34

Now that I think about it, I've never seen an NTR beyond that little silohuette behind the great jet of fire shown in the pictures taken during the tests at White Sands.

Do NTRs or for that matter, VSMIRs (forgot the acronym if thats wrong) even have engine bells?

-Matt

Shaun Barrett · 2003-01-25 01:06:08

Hi Nirgal82!

Yes, the NTR did have (and presumably will have again) a bell-shaped nozzle.

For a picture of one of the NERVA rockets of 30 years ago, click here. (You'll need to scroll down a little when you get there! )
They managed to produce 250,000lbs of thrust with one of the prototypes. I wonder if they still have any of them in mothballs.

Does anyone know how 'dirty' the exhaust was, in terms of radiation? Are modern designs likely to be 'clean' enough to enable ground launches?
If not, how about mid-ocean platform launches?

nirgal · 2003-01-25 10:26:27

nirgal82

I read that the engines actually burned hotter than the melting point of the materials used to build them, and that the fuel-as-coolant method was neccesary.

NTRs use regenerative cooling as well. Since Shaun's link didn't work for me I post a link to another picture of NERVA here:

http://www.f104g.demon.co.uk/space/nerva1.htm

nirgal · 2003-01-25 10:43:02

NASA Chief Outlines New Nuclear, Space Plane Efforts

nirgal · 2003-01-25 18:49:04

Found this picture:

Nirgal82 · 2003-01-26 17:32:35

So basically they turbo-pump hydrogen through a "hot" reactor core and direct it out the back?

Seems that those would be dirty rockets to me, unless theres some way that they can find a shielding that lets infrared energy through but not harmful radiation, or theres a clean "burning" nuclear fuel...

-Matt

Mark S · 2003-01-26 23:57:43

Although I have a nearly-nonexistant background in nuclear engineering, I would suppose that it's possible to build a "clean" NTR for ground launch.

In the same way that the heated, irradiated water from the reactor does not drive the turbine in a pressurized water reactor, I assume you could build an NTR according to the same principle. Hydrogen would be pumped through a heat exchanger loop that absorbs heat from the reactor's working fluid. I believe that Max Hunter's "RITA" SSTO used this approach.

Shaun Barrett · 2003-01-27 01:17:22

I suppose the Luddites would go into overdrive at the thought of NTR ground launches, even if it were possible to demonstrate a zero impact on the environment!
An NTR could probably be made less damaging to the surroundings than a Saturn V or the Shuttle, but just the word 'Nuclear' would be enough to get the usual knee-jerk reaction from 'The Mindless Ones'.

As a matter of fact, I read recently that the international anti-nuclear brigade has already mobilised to protest against Bush's nuclear propulsion plans - and they haven't even heard the speech yet!!
Where do they get 'em from?!

soph · 2003-01-27 07:42:25

In an article at spacedaily.com, Bruce Gangon actually talked about the pro-nuclear people "indoctrinating" the students of our country. What a joke! Those industries are the best at indoctrination, going on their marches and rallies without any real knowledge of what they are protesting.

nirgal · 2003-01-27 13:59:23

The Mars Society has issued a resolution supporting Project Prometheus.

www.marssociety.org

RobertDyck · 2003-01-27 14:44:48

Seems that those would be dirty rockets to me, unless theres some way that they can find a shielding that lets infrared energy through but not harmful radiation, or theres a clean "burning" nuclear fuel.

I my past blabbering (um, posts) about NTRs I tried to say that it can be done with clean exhaust. To start with, use the same ceramic capsules that Nerva used. That keeps the uranium and highly radioactive by-products inside the capsules. Liquid hydrogen is run through the reactor to heat it, and neutron radiation has to be moderated to enable neutron absorption by uranium; without that the reactor would not react. That means the hydrogen will pass through neutron radiation and will absorb some of it. If you use pure 1H as propellant, the exhaust will have some deuterium but no radioactive elements.

Any element that absorbs neutron radiation simply becomes the isotope of the same element with an atomic number one greater. The question is then whether that isotope is stable or if it decays. For example, oxygen 18O consists of 8 protons and 10 neutrons. When it absorbs another neutron it becomes 19O. That is not stable; one of the neutrons will release a high energy electron (beta radiation) to become a proton. Once a neutron converts into a proton the result will still have 19 subatomic particles in the nucleus, but 9 will be protons and 10 neutrons. The additional proton in the nucleus will increase the positive static charge, which will attract another electron. The additional electron will change its chemical behaviour; that is why the number of protons determines the element. The element with 9 protons is fluorine. That means oxygen 19O will beta decay into fluorine 19F. The half-life of 19O is 26.9 seconds, which means half of it will decay into 19F in 26.9 seconds, half of the remainder will decay in another 26.9 seconds, then half of those left-overs will decay in another 26.9 seconds, etc.

Hydrogen is a very simple element. 99.9885% of hydrogen atoms are just a single proton without any neutrons, so that has an atomic number of 1, so we write 1H. The other natural isotope is call deuterium which has 1 neutron for a total of 2 subatomic particles, we write 2H. Neutron absorption by 1H will become 2H. Neutron absorption by 2H will become 3H, which is tritium. If you want to avoid any tritium in the exhaust, then simply refine the hydrogen to remove all deuterium. Heavy water has deuterium instead of normal hydrogen. The left-over from separating heavy water from normal water is call light water. If you electrolysize light water the result will be oxygen and hydrogen 1H. That means the by-product of producing heavy water is pure 1H, suitable for nuclear rocket propellant.

GDavid · 2003-01-27 17:09:41

Though I just posted this in the Political Outreach area of this board (and on a few other boards), given the topic of this thread, it may fit here as well. No intention of 'spaming' btw.

Note that we've barely 24 hours left for some large-scale public pre-action to influence GWB's 'State of the Union' message which could announce this and more. A brief 'window of opportunity' is now in effect.

Mars Society ~Mars Direct joins bandwagon

Brief backstory here, as usual (due to long distance relationship) I was away from and not too active on the 'net this weekend. Seems 'stuff' usually happens on weekends though. So when I got home late last night was a bit of 'catch-up' to do on this Prometheus and SotU matter, kept me going till the wee hours of near dawn.

Reveiwed the mixed reactions of assorted boards, but made my main and limited posting initially over at the BBS for MarsNews.com, replying to Robert Williams openner there and exchanging a few with 'goatstory'. Along the way mussed about Zubrin and his Mars Society and Mars Direct crowd as a look at their website had nothing on this and what looks to be a recently openned BBS for them was also a bit quiet.

So I joined that BBS and started a thread in the Political Action forum on this matter of calls and letters to GWB at this last minute/eleventh hour. I also sent text of one of those posts to a name on the "Contacts" list at the 'Mars Society (Mars Direct)' website, one Brian Frankie, head of their "Political and Public Outreach Task Force" essentially asking him why they haven't "jumped onto this yet".

Haven't received a reply from him, but check the latest on the main board of Mars Society's website;
http://www.marssociety.org/
Looks like they may be getting in on the act, "jumping on the bandwagon" since this is now up in their 'news' section;
http://www.marssociety.com/news/2003/0127.asp

Now I'm not claiming that my e-mail sparked this development, it could have been actions of others or just a monitoring and 'wait see' approach finally got them going. Then again....

The flow of events in human affairs often offers as much chance to "build bridges" as it does to "burn bridges". Given the large membership of Mars Society~Mars Direct crowd and their greater potential for associated networks, along with their 'single minded focus' towards crewed Mars missions this may possibilly work to greatly increase those numbers.

Speaking of numbers, the Prez may propose national policies and directions, but it's Congress that approves such and especially the funding. I suspect GW wants to say he's heard from "tens of thousand of Americans" (if not and better yet, hundreds of thousands) who are supportive and on board towards this increased funding and purpose to not only NASA, but likely other 'private ventures', to get the ball rolling on increased space exploration and 'Missions to Mars'. Numbers sway and if GW has 'in hand' stacks of public response and support to back his State of the Union request and "mandate' then Congress will likely get on board.

Consider sending some follow-on and even pre-'heads-up' e-mails to your elected reps on this, letting them know you expect something will be revealed this SotU and you are for it.

It's the eleventh hour for this initative, 'fourth down and ten to go', we all need to move with a sense of purpose and urgency on this, get the word out, network, make any 'alliances' we can to add to the grassroots groundswell. Time to show what the 21st century and this new age of instant internet exchanges and communications can accomplish, time to empower the peoples of this nation and world on this matter.

[end of soapboxing for the moment]

Shaun Barrett · 2003-01-27 18:15:09

My apologies, Robert, for asking questions about clean exhaust from NTRs that you'd already answered elsewhere. I know how frustrating it can be to realise your well-intentioned arguments aren't getting through!
And your well-set-out refresher on basic nuclear physics, appropriate to this subject, was most welcome. Thank you.
I try not to ask too many dumb questions, but ... !!

And, GDavid, despite your self-effacing comments, I strongly suspect your efforts have been instrumental in waking them up at TMS !
Nice work!!
:;):

soph · 2003-01-28 19:16:01

its funny how we've tested bombs that have hundreds of kilotons of nuclear force, and yet the american southwest still exists.

soph · 2003-01-28 21:31:05

jee, no mention of prometheus in State of the Union. lets hope for a separate announcement, maybe after iraq and north korea are resolved.

this might give nasa a chance to develop something that they can unveil to the public for the announcement.

GDavid · 2003-01-28 22:26:25

soph,

Sure hope so. Anyone who knows the world situation should realize these two are the only nations currently threatening world stability. Once 'neutralized', the ongoing 'Terrorism' threat is mostly a low-profile "Special Forces" sort of operation, so time, focus and budget should open up.

In the meantime, keep up the pressure and effort to increase public awareness, interest, and support for crewed missions to Mars.

"If we don't go, we won't know." the future that awaits us beyond this planet.

Mark S · 2003-01-28 22:28:11

I don't think you will see a formal announcement from the president on the issue. This is more of O'Keefe's "sphere of influence." And I certainly feel that President Bush does not like to "change subjects"--he repeats his same arguemnts until he achieves results. He's never spoken about space before, and I doubt he will bring it up before Iraq and the economy are fixed.

nirgal · 2003-01-29 05:30:49

From nasawatch.com:

Well, there was no mention of space, nuclear rockets, or Mars in the President's State of the Union address. None the less, this does not mean that interesting news for NASA is not in the offing. Exciting stuff will be announced next Monday. Yes, per earlier rumors, it involves spacecraft using advanced nuclear power sources - and the overall development program for these systems is dubbed "Prometheus". It's just that multiple destinations - other than Mars - are involved.

The announcements made next Monday will show that NASA, at least under this Administration, is no longer incapable of big thinking when it comes to space. Moreover, NASA's other reseach priorities are no longer politically beholdent to the shadow cast by the ISS program. Finally, NASA is now seen as being worthy of big things beyond the ISS - and the ISS itself is finally going to be seen as a stepping stone for things to come.

Would any of this have been forseen a scant 14 months ago? Stay tuned.

TJohn · 2003-01-29 07:33:43

Yeah, I was kind of looking forward to hear something but once Pres. Bush got past the hydrogen fueled cars, I knew it wasn't going to be announced. However, it's good to hear that something will be announced next Monday.

GOM · 2003-01-29 13:19:33

He's never spoken about space before, and I doubt he will bring it up before Iraq and the economy are fixed.

Attempting to "fix" Iraq may take a long time....

.02

GOM · 2003-01-29 13:25:15

once Pres. Bush got past the hydrogen fueled cars, I knew it wasn't going to be announced.

Pardon a quick hijack, but what did Bush say about hydrogen cars? I haven't heard anyone else comment on that point.

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#51 2003-01-24 17:31:32

Re: NASA eyes nuclear-powered rocket

#52 2003-01-24 18:08:33

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