Finishing up NERVA - how long would it take?

[ScallopPotato]

Linking to the wiki page on NERVA for some reference

And the atomic rockets page on solid core NTRs

Many of you know that the NERVA rockets being tested in the 60s and 70s were highly successful, with the NERVA XE and Pewee (the basis for the LV-N in KSP) almost ready to become flight prototypes. All the mars missions proposals during or after the NERVA project were based off of the tested rockets.

So if Congress appropriated funding to make flight prototypes of those designs and finish up the work in the NERVA project, how long would that take? Not including set-up time, I imagine the rockets would be ready for a full flight test within 5 years of starting work.

[MaverickSawyer]

It'd take a lot longer, because you'd have to redesign the engine, the tooling, the test facility, etc. NERVA was cutting edge for it's time, but we have a much better understanding of how materials react to being placed under high neutron flux and temperatures, so some of the materials used would have to be replaced. The manufacturing process for the engine would be revised to take advantage of new techniques and technologies. And you'd have to design a closed test cell to avoid contamination (You say the word "nuclear" in the US, and the NIMBYs come out of the woodwork like ants from under a log...)

I suspect it'd be a minimum of a 10 year program, provided the president and Congress who started the project were still in power after 8 years. If the president doesn't get reelected, kiss the program goodbye.

[Nibb31]

Agreed. You would pretty much have to start from scratch. Each part would have to be redesigned to fit current manufacturing, testing, and sourcing processes.

[Ralathon]

While they'd basically have to start from scratch, the fact that there was a working prototype 40 years ago will inspire a lot of confidence into the program. So they wouldn't have to worry much about getting their funding cut due to a lack of trust.

What: Build a nuclear rocket engine.

Why: Higher efficiency allowing bigger payloads for lower costs.

When: About 10 years of R&D.

Return of Investment: Nuclear rocket engine.

It is nice and straightforward without nebulous goals and payoffs. The problem is getting it started, people generally freak out about everything nuclear powered.

[Seret]

Rough ballpark I'd say 10 years for a flight prototype. Wouldn't be surprised to see it stretch out to 15 or 20 though, as there would be a lot of oversight and they'd need to be quite conservative with their testing programme and any problems they encountered.

[Nibb31]

NERVA isn't a miracle solution though. It was envisioned as a replacement for the S-IVB used on Apollo. The S-N would have been lighter and more efficient, but it would have had only 25% of the thrust of the S-IVB.

S-IVB: 120 tons, 1000kN thrust, Isp 421s.

S-N: 53 tons, 255kN, Isp ~800s.

Less thrust means that it would have had to burn longer to impart the same dV. All in all, there was some gain due to the higher Isp, but the biggest performance increase was because it was less that half the weight of a full S-IVB.

In the end, it would have been much more complex, much more expensive, and more delicate to handle and integrate at the pad. The considerable increased complexity wasn't deemed worth it.

Edited May 9, 2014 by Nibb31

[Streetwind]

Any project attempting to build an NTR should start over from scratch. The NERVA as a first generation solid core reactor prototype simply wasn't very good as far as NTRs go. Granted, it could be noticably better than chemical rockets in the right applications, ut the point is: you can do a lot better with modern technology.

I'd vote to ditch the NERVA concept entirely and instead look at gas-core nuclear lightbulbs. You would ostensibly have to add a feasibility study, but such work can be done in preliminary in the lab. Thus if it turns out the concept is a stillbirth, you can axe the project early without having to spend huge sums on building prototypes. But from existing materials it would seem like there are no major technological hurdles, and an engine like this will double up on Isp compared to a solid core design.

[Nuke]

when people ask "what good is a moon base" the first thing i can think of is "place to manufacture nuclear engines in an environment free of hippies".

best usage scenario would be for a reusable transfer vehicle. isru would be needed to fill its propellant tanks. i think an ideal engine would be one that can run with a multitude of propellant options so it can top off its propellant tanks at almost any body in the solar system.

Edited May 9, 2014 by Nuke

[peadar1987]

I wouldn't be too surprised if the Indians or the Europeans were the first to build a functional nuclear rocket engine. In particular, the ESA would in theory have access to the vast nuclear expertise of the French, which would be immensely useful.

Even if the ESA has no short to medium term plans to travel to Mars and beyond on their own, it would be an excellent bargaining chip for use in a partnership, or even to sell to the Chinese.

[Nuke]

that sounds more like something the chinese would do. they have the least problems with protesters.

[Nibb31]

I wouldn't be too surprised if the Indians or the Europeans were the first to build a functional nuclear rocket engine. In particular, the ESA would in theory have access to the vast nuclear expertise of the French, which would be immensely useful.

Even if the ESA has no short to medium term plans to travel to Mars and beyond on their own, it would be an excellent bargaining chip for use in a partnership, or even to sell to the Chinese.

Yes, but expertise in power plant engineering doesn't translate into expertise in propulsion systems. Besides, Europe is vastly anti-nuclear these days, especially Germany. No way would ESA ever build a nuclear rocket engine.

Edited May 9, 2014 by Nibb31

[Red Iron Crown]

The timeframe would entirely depend on how vigorously it was funded. A Manhattan Project-style push without regard for cost could probably have working prototypes within a year or two and functional spacecraft another year after that.

It'll never happen, as that level of funding commitment is highly unusual outside of wartime projects, but if some circumstance arose that made us believe it was needed ASAP, it could happen fairly quickly.

[Jouni]

It depends on the budget and the urgency.

The Manhattan Project delivered a product in 3-6 years, depending on which starting point you choose. For the Apollo program, it took 8 years. The Space Shuttle flew in 13-14 years.

[peadar1987]

that sounds more like something the chinese would do. they have the least problems with protesters.

Public opinion in France is actually overwhelmingly in favour of nuclear power. I mean, a few crusties blocking the tracks to La Hague every now and again doesn't stop them generating 75% of their energy from nuclear, and looking at expanding that capacity.

[Aghanim]

NERVA isn't a miracle solution though. It was envisioned as a replacement for the S-IVB used on Apollo. The S-N would have been lighter and more efficient, but it would have had only 25% of the thrust of the S-IVB.

S-IVB: 120 tons, 1000kN thrust, Isp 421s.

S-N: 53 tons, 255kN, Isp ~800s.

Less thrust means that it would have had to burn longer to impart the same dV. All in all, there was some gain due to the higher Isp, but the biggest performance increase was because it was less that half the weight of a full S-IVB.

In the end, it would have been much more complex, much more expensive, and more delicate to handle and integrate at the pad. The considerable increased complexity wasn't deemed worth it.

In KSP, the decision to use LV-N or chemical engine is decided by the payload mass. Now, there is a graph that shows when LV-N is more efficient than LV-T30, but I don't know where it is. Probably Apollo isn't heavy enough to justify nuclear engine. And no one is sure how to insert fuel into nuclear lightbulb, look at Project Rho

And its amazing what we could do if we could remove uninformed protesters from the equation...

[Nibb31]

Public opinion in France is actually overwhelmingly in favour of nuclear power. I mean, a few crusties blocking the tracks to La Hague every now and again doesn't stop them generating 75% of their energy from nuclear, and looking at expanding that capacity.

Public opinion is as anti-nuclear as anywhere else. The fact that France produces 75% of its electricity from nuclear is due to political decisions made in the 60's. Current policy is to bring the figure down to 50% or lower.

[ScallopPotato]

Another difference between NERVA and a modern NTR is that they won't be used as an upper stage like Saturn S-N. Stephen Baxter's Voyage gives a pretty good reason why not to do that. Any NTR stage would be inside the fairing of a large rocket with the control rods deep in the reactor. The control rods wouldn't be removed and the reactor powered up until after they're checked out and cleared in a parking orbit. I probably wouldn't power them up until the ship has it's payload and is ready to depart.

Radioactivity doesn't really pick up in the reactors until they've completed the TMI/TVI/TJI/TLI burns. Think of an unfired reactor like fresh firewood. If nuclear fuel is firewood, then an always active RTG is like a candle. The only conceivable threat to Earth is if a returning Crew Transfer Vehicle is on a collision course with the Earth. I'm thinking the main threat the NTRs pose is to the crew, when they're far away from Earth. I'm sure they'll be lengthy studies done about safety.

[Nibb31]

The S-IVB had to burn to circularize into the parking orbit before TLI. With the S-N being lighter than the S-IVB meant that the S-II could burn all the way to circularization so that the S-N would only have been started after checkout in orbit.

[peadar1987]

Public opinion is as anti-nuclear as anywhere else. The fact that France produces 75% of its electricity from nuclear is due to political decisions made in the 60's. Current policy is to bring the figure down to 50% or lower.

Ah right. I suppose my previous information was from my time at EDF, so there is just a tiny chance they might be biased in favour of nuclear!

[theend3r]

Public opinion is as anti-nuclear as anywhere else. The fact that France produces 75% of its electricity from nuclear is due to political decisions made in the 60's. Current policy is to bring the figure down to 50% or lower.

That's quite sad. Nuclear power is the most green and eco firendly after all. Far more so than destroying your landscape with wind turbines or solar fields (plus the pollution from their production), which aren't even stable. I guess this is one of the pitfalls of democracy.

[Idobox]

That's quite sad. Nuclear power is the most green and eco firendly after all. Far more so than destroying your landscape with wind turbines or solar fields (plus the pollution from their production), which aren't even stable. I guess this is one of the pitfalls of democracy.

As a Frenchman, I really hope we learn from Germany. Stopping nuclear resulted in massive increase of electricity cost, pollution and dependency on foreign countries, and they're not finished yet.

Also there isASTRID, a planed sodium fast neutron surgenerator that should produce 600MWe while burning waste. If it works as planned, we would have the perfect tool to convince people to build nuclear power plants (nuclear waste? you mean free fuel?)

[peadar1987]

That's quite sad. Nuclear power is the most green and eco firendly after all. Far more so than destroying your landscape with wind turbines or solar fields (plus the pollution from their production), which aren't even stable. I guess this is one of the pitfalls of democracy.

Well, I would disagree with that. Nuclear is inherently risky, and uranium mining is a very messy process. It's far, far better than coal or oil, but that's not really saying that much.

The best option is probably nuclear and biomass for base load, supplemented by offshore wind, wave, and tidal, or solar. And of course, the big one, energy efficiency. Use the waste heat from power stations for district heating or cooling, change building codes and provide grants for more efficient heating systems and insulation, follow a policy of distributed generation and smart grids, then we'd be getting somewhere.

Unfortunately, governments work on a 5 year cycle. Anything that's not going to show tangible results in the few key battlegrounds within 5 years is far less likely to be implemented, which is sad.