Why aren't we using nuclear thermal rockets?

[magnemoe]

38 minutes ago, winged said:

Exactly, our missions aren't ambitious enough to justify the development cost for nuclear engine. Even if NTR engines were available here and now without any complications such as radiation, I still don't see them to be used for what we do today: launching probes to nearest planets, asteroids and crewed LEO expeditions. The only application that I am able to find is to transfer small probes (3-6 metric tons) directly to Jupiter and Saturn without relying on gravity assists. That would require creating a small Centaur-like nuclear upper stage for Atlas rockets. But you can get around that simply by using larger rockets - SLS for instance is supposed to launch Europa Clipper directly towards the destination. Oh and we launch probes to outer planets only once per 10 years or so - it's hard to imagine developing such hardware just to be used once per decade.

This, now add that new Glen with its huge fairing would be perfect for this, and the obvious elephant as in BFR, how large two stage rocket you you put in the cargo hold? Methane+LOX first stage for injection and an hypergolic for braking at target, you can fill up the first stage in LEO and even use the BFR upper stage itself as an tug to get it close to earth escape velocity.

Finally all the politic does not apply for Russia or China, we cooperate closely with Russia and are buying launch services from them. 
In short an lack of marked, add that other engine models who can either use solar or an reactor, even an combination seems more relevant today for high ISP engines. 

[tater]

5 hours ago, Green Baron said:

There is still far too much irrationality and constructed arguments involved. "People dying working for solar power" is non argument, and totally turns against the arguer.

No, people die in every industry. They get run over in the parking lot, etc. People die working at Walmart at a baseline rate (a very, very low rate, workplaces are generally pretty safe). In the case of solar, the risky bits of employment in the industry are probably people working in construction, installing panels on rooftops. That has a non-zero (but again, quite low) death rate. Add up all these tiny numbers of deaths, and divide by the power produced. Do the same for nuclear, coal, etc. Nuclear and solar are both very, very low when this calculation is done, some tiny fraction of a death per terawatt produced, coal is some larger number of dead people per terawatt (10s or hundreds as I recall, orders of magnitude higher than solar/nuclear, at any rate).

5 hours ago, Green Baron said:

Yes, dusting them is the only periodic (once a year here) maintenance they need. Which could be partly achieved with a repellent surface and electrostatic.

The MAV (Mars baseline mission architectures for NASA) has to make propellant. It must robotically deploy panels to generate large amounts of power, and then it must clean them. Who is going to dust them, the solar-powered deployment robot?

 

1 hour ago, winged said:

Exactly, our missions aren't ambitious enough to justify the development cost for nuclear engine. Even if NTR engines were available here and now without any complications such as radiation, I still don't see them to be used for what we do today: launching probes to nearest planets, asteroids and crewed LEO expeditions. The only application that I am able to find is to transfer small probes (3-6 metric tons) directly to Jupiter and Saturn without relying on gravity assists. That would require creating a small Centaur-like nuclear upper stage for Atlas rockets. But you can get around that simply by using larger rockets - SLS for instance is supposed to launch Europa Clipper directly towards the destination. Oh and we launch probes to outer planets only once per 10 years or so - it's hard to imagine developing such hardware just to be used once per decade.

The primary point of NTP in any short (next X decades) timeframe is crew missions to Mars, not small space probes, not crew missions to LEO or even the Moon.

Nuclear power (electric) is useful for lunar base architectures, and is pretty much required for crew missions to Mars (Kilopower, etc).

Edited December 21, 2018 by tater

[winged]

54 minutes ago, tater said:

The primary point of NTP in any short (next X decades) timeframe is crew missions to Mars, not small space probes, not crew missions to LEO or even the Moon.

I know what they're supposed for, I was only trying to list the applications for NTR assuming that they're available here and know without any additional problems related to them. It turned out that there aren't many applications because everything what can be done with current NASA budget is doable with chemical propulsion. Crewed Mars expeditions are probably beyond budget and political will and having nuclear engines available right now wouldn't change that.

 

In other words what's the point of developing NTR if we wouldn't go to Mars anyway.

Edited December 21, 2018 by winged

[DDE]

43 minutes ago, magnemoe said:

Finally all the politic does not apply for Russia or China

You're about to make me drop everything and try to calculate an upper stage powered by bundled-up Burevestnik/Poseidon reactor piles.

Don’t. I’ve already coaxed something like 18 t to LEO from a Soyuz-3 (expanded 2.1v-style core) with Syntin-FLOX-70 propellants. That’s enough mad science this year.

Also, regarding nuclear reactors falling out of the sky, this bit is pertinent for this thread.

 

Edited December 21, 2018 by DDE

[Green Baron]

33 minutes ago, tater said:

Nuclear power (electric) is useful for lunar base architectures, and is pretty much required for crew missions to Mars (Kilopower, etc).

You keep saying that, but in my opinion it is not true. Solar panels can generate similar power/mass at Mars, last longer, need less maintenance, and do not leave a poisonous heritage for billions of years (43kg U235/unit: 700My halflife). If you say manned missions then there are the ones who clean them (should it be necessary at all and if it can't be done constructively). In my opinion this is rather a political decision then a technlogical one.

And, btw. solar panels are fabricated fully automated. Do more solar panel workers die in parking lots than others ? If there is anything to that argumentation "people die everywhere" this must be case.

Edited December 21, 2018 by Green Baron

[tater]

23 minutes ago, winged said:

I know what they're supposed for, I was only trying to list the applications for NTR assuming that they're available here and know without any additional problems related to them. It turned out that there aren't many applications because everything what can be done with current NASA budget is doable with chemical propulsion. Crewed Mars expeditions are probably beyond budget and political will and having nuclear engines available right now wouldn't change that.

In other words what's the point of developing NTR if wouldn't go to Mars anyway.

Fair enough, I don't disagree, actually.

That said, the NTP people at NASA could fly a small test article for very little budget input, they've done ground testing. This is exactly what NASA should be doing instead of wasting money on SLS/Orion, honestly. They should develop the technologies that the market is unlikely to do quickly on its own, and nuclear really fits this due to regulatory issues. Making NTP a high TRL would possibly be useful in the not too distant future.

[magnemoe]

21 minutes ago, Green Baron said:

You keep saying that, but in my opinion it is not true. Solar panels can generate similar power/mass at Mars, last longer, need less maintenance, and do not leave a poisonous heritage for billions of years (43kg U235/unit: 700My halflife). If you say manned missions then there are the ones who clean them (should it be necessary at all and if it can't be done constructively). In my opinion this is rather a political decision then a technlogical one.

And, btw. solar panels are fabricated fully automated. Do more solar panel workers die in parking lots than others ? If there is anything to that argumentation "people die everywhere" this must be case.

Mars yes solar would be just as good, 10 hour night and you can go to low power mode during it turning off ISRU and other power hungry stuff. And its an more distributed system so if one solar panel break its just an tiny reduction in capacity. 
Moon however has an 14 day night, and unlike Mars you an abort and return at any time here you need an reactor for anything more than an outpost. 

And talking about radiation pollution in space is pretty pointless as the environment is radioactive. its only relevant for stuff crashing down on earth. 

[tater]

1 hour ago, Green Baron said:

You keep saying that, but in my opinion it is not true. Solar panels can generate similar power/mass at Mars, last longer, need less maintenance, and do not leave a poisonous heritage for billions of years (43kg U235/unit: 700My halflife). If you say manned missions then there are the ones who clean them (should it be necessary at all and if it can't be done constructively). In my opinion this is rather a political decision then a technlogical one.

All current NASA DRMs have the ascent vehicle landing years ahead of time to produce propellants. If a storm covers the panels, they then must start over, since they're not sending crew to dust off the panels, what about this is hard to understand?

They can send the MAV, and cross their fingers, but when the crew launch window appears 2.14 years later, if there has been a really bad storm that slows/stops prop production, they have to not send crew, and instead send a new MAV. Given the huge cost of each launch, nuclear makes more sense.

 

Quote

And, btw. solar panels are fabricated fully automated. Do more solar panel workers die in parking lots than others ? If there is anything to that argumentation "people die everywhere" this must be case.

More people do not need to die. Just the regular number.

Every single human organization has a (usually incredibly low) accident/fatality rate. The total number who die are that rate (x deaths/worker) times the number of workers. Solar is a distributed tech for the most part (many houses near me have panels, for example), so the total number of people involved in the industry is large for the relatively small amount of power produced.

If 1 worker dies in the entire worldwide solar industry every 10 years, then there is (1 death)/(total solar power production*10) deaths/W. That's currently like 300 GW/yr, so it would be  0.33 deaths/tW. The actual number is about an order of magnitude lower than that (deaths/tW). The value for nuclear is similar (and includes estimated excess cancer deaths, and all historical deaths from accidents, etc). Nuclear has great mortality/tW not because it is inherently safer, but because it makes so very much power. Humanity needs more and more electricity, so any power not created with nuclear has to be created by another source. Solar is in the same safety ballpark as nuclear, but still requires backup sources of power, virtually all of which are considerably less safer/power than nuclear. It's important to note that nuclear safety is based on extant reactors, and modern (sadly unbuilt) designs are far safer than Generation I - II plants (and even Gen III - III+, really).

Solar and nuclear are both ridiculously safe per unit power produced. A few hundreths of a death per terawatt.

Edited December 21, 2018 by tater

[IncongruousGoat]

Yeah, but nuclear accidents look really dramatic and scary. It's like aircraft - flying is, statistically, by a very large margin, the safest way to travel. People still fear it a lot more than travel by car, or train, because when a plane crashes it's really dramatic, and there are lots of movies about airplane disasters. The availability heuristic is what people use for risk assessment, and it's coincidentally really bad for risk assessment.

So our fundamental problem is that people don't understand statistics or risk assessment. But we knew that.

[Green Baron]

I'd say, apart from the 3-4 real big ones and dropping of bombs, nuclear accidents don't actually leave much of a visible trace. Additionally waste disposal, civil reactors and connected material, military equipment and other radiating stuff will still be a problem in a long time, when humans will not be there any more. The technology is too difficult to handle technically and socially and meanwhile simply outdated imo, can be easily replaced by renewable energy on earth if there was the will.

A common effect that can be observed in everything that is hard to quantify or touches politics/lobbyism, that cemented opinions remain, well, that :-)

I must admit, when i was younger i found all that stuff much more fascinating than today. As a student i worked for a heat treatment company between semesters and i have seen how safety is interpreted when it comes to time and money.

-----------

If i get it right, the main reasons why NTRs aren't in use now are probably political/social, technological progress since then may also play a role. For now, there is no need to develop an updated version as nobody is going past LEO any time soon and chemical launchers with the necessary oomph are on the horizon and can be realized for much less and in a much shorter time, if development isn't completely messed up. Also, for those who like to colonize, i find the research of other subjects much more pressing than power conversion, like nutrition, health, raw materials, maintenance, shielding, blabla. All subjects that lack a solution much more than propulsion or energy supply, or not ?

Edited December 21, 2018 by Green Baron

[DDE]

13 hours ago, IncongruousGoat said:

Yeah, but nuclear accidents look really dramatic and scary.

There’s a bit of a twist: tye primary damaging factor is invisible. Literally.

Which makes the incidents even more scary.

11 hours ago, Green Baron said:

technological progress

In a roundabout way, namely probes. Back in the day they thought a Mars probe required a manned flyby.

11 hours ago, Green Baron said:

Also, for those who like to colonize, i find the research of other subjects much more pressing than power conversion, like nutrition, health, raw materials, maintenance, shielding, blabla. All subjects that lack a solution much more than propulsion or energy supply, or not ?

Well, a better form of propulsion would relieve the Tyranny of the Rocket Equation, which compounds most of the problems above with the necessity to limit your inbound shipping. And a lot of the research - especially related to gravity - would have to be done in situ sooner or later.

There emphatically is a place for flag-and-footprints in between probes and colonization.

[Green Baron]

53 minutes ago, DDE said:

There emphatically is a place for flag-and-footprints in between probes and colonization.

Absolutely ! With a geoscience background, I am really looking forward to sending real people to places. Probes are nice for collecting basic data for interpretation but can by no means replace well equipped and prepared human specialists.

For Mars for example i actually think that chemical rockets with their high thrust are the better choice, because they minimize travel and so exposure time as well as time in microgravity for the crew in comparison to low thrust nuclear rockets, and so minimize the health risks.

But i don't see people flying to Mars in the next 2 decades, maybe longer. And by then things may look different.

Edited December 22, 2018 by Green Baron

[Xd the great]

The idea of dropping radioactive material onto enemy positions and disguising it as a failed rocket launch is VERY appaling.

So we have a treaty.

[Green Baron]

Fusion drives are better but >>30 years away.

Edited December 22, 2018 by Green Baron

[Kerbart]

14 hours ago, IncongruousGoat said:

So our fundamental problem is that people don't understand statistics or risk assessment. But we knew that.

It goes a bit deeper than that:

• The nuclear industry chose to ignore the fact that properly understanding risk assessment is really hard for the masses
• The nuclear industry also chose to advertise itself with terms as “perfectly safe” while cutting corners on design and execution. From a statistical point of view, the track record is great; see point one. They're focusing on the wrong metric. It's like complaining you didn't win the 100m sprint. "But I took the least amount of steps!” Yeah, but that's not what it's about...
• As @DDE mentioned, radiation is invisible, so the public has to trust experts on what they're saying. Trust that got breached continuously

If your teenage child has a history of throwing multiple wild parties in your house while you're out, would you leave him unsupervised for another weekend when you need a break? “Trust me dad, I've learned my lesson. I won't do it again. I don't need supervision.” Hey, we want to fly a nuclear reactor over your head in space. But trust us, nothing can happen.

It's easy to blame the nimbies and treehuggers, but let's not forget that in the late 1950s and early 1960s the vast majority of the population had no problem with nuclear power. It's not that the nuclear industry had a problem gaining the trust of the people; they lost it. That's a lot harder to get back.

The public resistance against launching nuclear reactors in space is irrational. It's also understandable. And the same industry that blames them for standing in the way of progress is the one that got themselves there in the first place.

[DDE]

5 hours ago, Green Baron said:

For Mars for example i actually think that chemical rockets with their high thrust are the better choice, because they minimize travel and so exposure time as well as time in microgravity for the crew in comparison to low thrust nuclear rockets, and so minimize the health risks.

Compared with the alternatives, the thrust of NTRs is not materially different from chemicals. Both have effectively instant burn times compared to the trip duration.

[kerbiloid]

5 hours ago, Kerbart said:

properly understanding risk assessment is really hard for the masses

for any technology which can't be done at home.

Masses will always say: "No, too dangerous. We need moar researches."

5 hours ago, Kerbart said:

If your teenage child has a history of throwing multiple wild parties in your house while you're out, would you leave him unsupervised for another weekend when you need a break? “Trust me dad, I've learned my lesson. I won't do it again. I don't need supervision.” Hey, we want to fly a nuclear reactor over your head in space. But trust us, nothing can happen.

The problem is: you are almost always wiser than a child. A child will get wiser. Unlike nukers and masses. The nukers will always stay wiser, and the masses will be always saying "nope".

I believe, the main hope of the nuclear energetics is the green one: solar panels, wind, etc.
"Tree huggers" are the best friends of the nuclear energetics.

P.S.
Unlikely invisibility plays any role at all.
Luddites were crashing looms. Then they were hating steam engines, cars, so on. Whatever can't be done by hands from garbage found by the side of the road.

Edited December 22, 2018 by kerbiloid

[DDE]

1 hour ago, kerbiloid said:

I believe, the main hope of the nuclear energetics is the green one: solar panels, wind, etc.

Guess what pie has Rosatom fingers in it.

1 hour ago, kerbiloid said:

Luddites were crashing looms.

And we are NOT talking about actual luddites. The actual luddites today are those concerned with jobs and automation. As they were back in the day.

[kerbiloid]

20 minutes ago, DDE said:

Guess what pie has Rosatom fingers in it.

I mean, on the worldwide scale.

I believe, the environmentalist fanatics are the stormtroopers, the zerg rush, the ultramarines of the Blessed Atom.
They are cleaning the construction place from the obsolete archaics.
They are to force the humans accept the electricity instead of dieselpunk, to replace the fuel stations with power stations, the gas cars with electrocars.
They are doing this by propagating the "green energy", by fearing the unbelievers with the carbon dioxide and the global warming.

After they do this, and after the humanity has replaced pipes with wires, combustion with electricty, the light of the true way will reveal itself.

The green energetics will get bankrupted and collapse under the weight of the global energetics, and the Blessed Atom will generously replace those ridiculous suncatchers and windmills behind the power line sources, using the ready electric infrastructure to propagate its might and goodness.

As this will happen not right now, but once the hydrocarbon energetics has gotten replaced with the electric one, so 20-30 years later, at that moment there will be more smart and effective nuclear plants than now.
So, the Atomic Energy will be the unopposed choice, as well as the cosmonukes.

 

Edited December 22, 2018 by kerbiloid

[wumpus]

20 hours ago, kerbiloid said:

The problem is: you are almost always wiser than a child. A child will get wiser. Unlike nukers and masses. The nukers will always stay wiser, and the masses will be always saying "nope".

I'm not sure where you live, but to develop a nuclear plant in the US (without bankrupting the power company that builds it) would pretty much require throwing the entire nuclear regulatory environment in the trash (mainly to kill the "nuclear industry" that currently exists) and rewrite it in such a way that the commercial construction industry (who are certainly no angels themselves, but at least don't bankrupt *everything* they touch)  can build the new plants.  I can't imagine the politics behind this (never mind the "masses", just imagine how many jobs will cease to exist both in the DOE and the "nuclear industry") and I'm sure it won't happen until the nuclear industry simply doesn't exist to object.

I bring up the idea of "technology is what the infrastructure can produce" in discussions of the historical development of science and tech, but here it is blatantly in the present.  The US (and most of the West) simply doesn't have "the technology" to build a nuclear plant anywhere near profitable (not sure how Norway did it in the 1990s or so, but good luck letting them build those without worrying about local regulations elsewhere), thanks to the nuclear industry and the regulations that make sure they are the only ones capable of building nuke plants.  You are far, far better off building wind and/or solar plus batteries than you are building a nuclear plant (and the batteries are a hard sell when you are already building cost effective natural gas plants [ignoring the carbon]).

Check the cost/kWhr coming out of any recent (or even not-so-recent) US nuclear plant: they are unmitigated disasters.  Not only that, but any attempt for the nuclear industry to "catch up" (say if Lockheed *did* manage to build fusion reactors), it still has to race against rapidly less expensive (in terms of power generated) solar and wind plants (although I suspect that ideal wind locations are already in use).  Public perceptions of safety are at best a tertiary problem for nuclear plants (unless you are talking about having Chinese construction companies build to Chinese standards): the cost is simply impossible to justify.

I understand the Chinese are doing fine in nuclear plant construction, but high profile failures* make even moderate naysayers hardly willing to allow Chinese construction of nuclear plants (built to Chinese regulations).

Yes, this entire rant is largely the reaction of a former "true believer" in nuclear power (I still think it is a great idea, just that it pretty much has to start again from scratch.  Perhaps with either "hot pebbles" or fusion).  When global warming was first discovered as a problem in the 1980s (and confirmed as a certainty in the 1990s, if not earlier), it was clear that nuclear power should have been our savior (from memory Norway was the only country to meet the Tokyo accords, and only by building "not allowed by the Tokyo accords" nuclear plants).  Unfortunately, people preferred to put their heads in the sand and the nuclear industry decided that the way to survive was to maximize the cost of the plants they were already building.  By now there is no way that nuclear power can deliver its carbon-free power in time to avoid massive environmental damage.

* to be honest, recent Chinese construction is mind boggling in scope.  The only thing I can compare it to was 19th century US construction, and our bridges were collapsing left and right then.  When you are constructing entire cities at once, having a few buildings collapse seems reasonable.  But considering the "locals examining hydrazine powered boosters" threads, I can't imagine many western nations willing to have nuclear plants built to Chinese regulations.

[Bill Phil]

On ‎12‎/‎22‎/‎2018 at 6:31 AM, Kerbart said:

It goes a bit deeper than that:

• The nuclear industry chose to ignore the fact that properly understanding risk assessment is really hard for the masses
• The nuclear industry also chose to advertise itself with terms as “perfectly safe” while cutting corners on design and execution. From a statistical point of view, the track record is great; see point one. They're focusing on the wrong metric. It's like complaining you didn't win the 100m sprint. "But I took the least amount of steps!” Yeah, but that's not what it's about...
• As @DDE mentioned, radiation is invisible, so the public has to trust experts on what they're saying. Trust that got breached continuously

If your teenage child has a history of throwing multiple wild parties in your house while you're out, would you leave him unsupervised for another weekend when you need a break? “Trust me dad, I've learned my lesson. I won't do it again. I don't need supervision.” Hey, we want to fly a nuclear reactor over your head in space. But trust us, nothing can happen.

It's easy to blame the nimbies and treehuggers, but let's not forget that in the late 1950s and early 1960s the vast majority of the population had no problem with nuclear power. It's not that the nuclear industry had a problem gaining the trust of the people; they lost it. That's a lot harder to get back.

The public resistance against launching nuclear reactors in space is irrational. It's also understandable. And the same industry that blames them for standing in the way of progress is the one that got themselves there in the first place.

While you're not wrong, there have also been many smear campaigns and plenty of anti-nuclear protests that were paid for by the oil and coal industries. Not only that, but China Syndrome came out weeks before Three Mile Island, and that certainly didn't help anything. Plus, the word nuclear is used both for reactors, and for bombs. And a good number of people don't like that, so they associate reactors with bombs, eventually. After that it's not hard to see how someone could begin to believe certain things about nuclear power.

Flying a reactor in space is a different beast, though. While I definitely think nuclear is pretty much our best bet for getting anywhere beyond the Moon, it's not likely to be used. The only thing I can think of that would minimize risk would be to distribute the nuclear fuel launches so that there's very little per launch, and if there's a failure only a little bit is released into the environment. And that would balloon costs like crazy.

4 hours ago, wumpus said:

I'm not sure where you live, but to develop a nuclear plant in the US (without bankrupting the power company that builds it) would pretty much require throwing the entire nuclear regulatory environment in the trash (mainly to kill the "nuclear industry" that currently exists) and rewrite it in such a way that the commercial construction industry (who are certainly no angels themselves, but at least don't bankrupt *everything* they touch)  can build the new plants.  I can't imagine the politics behind this (never mind the "masses", just imagine how many jobs will cease to exist both in the DOE and the "nuclear industry") and I'm sure it won't happen until the nuclear industry simply doesn't exist to object.

I bring up the idea of "technology is what the infrastructure can produce" in discussions of the historical development of science and tech, but here it is blatantly in the present.  The US (and most of the West) simply doesn't have "the technology" to build a nuclear plant anywhere near profitable (not sure how Norway did it in the 1990s or so, but good luck letting them build those without worrying about local regulations elsewhere), thanks to the nuclear industry and the regulations that make sure they are the only ones capable of building nuke plants.  You are far, far better off building wind and/or solar plus batteries than you are building a nuclear plant (and the batteries are a hard sell when you are already building cost effective natural gas plants [ignoring the carbon]).

Check the cost/kWhr coming out of any recent (or even not-so-recent) US nuclear plant: they are unmitigated disasters.  Not only that, but any attempt for the nuclear industry to "catch up" (say if Lockheed *did* manage to build fusion reactors), it still has to race against rapidly less expensive (in terms of power generated) solar and wind plants (although I suspect that ideal wind locations are already in use).  Public perceptions of safety are at best a tertiary problem for nuclear plants (unless you are talking about having Chinese construction companies build to Chinese standards): the cost is simply impossible to justify.

I understand the Chinese are doing fine in nuclear plant construction, but high profile failures* make even moderate naysayers hardly willing to allow Chinese construction of nuclear plants (built to Chinese regulations).

Yes, this entire rant is largely the reaction of a former "true believer" in nuclear power (I still think it is a great idea, just that it pretty much has to start again from scratch.  Perhaps with either "hot pebbles" or fusion).  When global warming was first discovered as a problem in the 1980s (and confirmed as a certainty in the 1990s, if not earlier), it was clear that nuclear power should have been our savior (from memory Norway was the only country to meet the Tokyo accords, and only by building "not allowed by the Tokyo accords" nuclear plants).  Unfortunately, people preferred to put their heads in the sand and the nuclear industry decided that the way to survive was to maximize the cost of the plants they were already building.  By now there is no way that nuclear power can deliver its carbon-free power in time to avoid massive environmental damage.

* to be honest, recent Chinese construction is mind boggling in scope.  The only thing I can compare it to was 19th century US construction, and our bridges were collapsing left and right then.  When you are constructing entire cities at once, having a few buildings collapse seems reasonable.  But considering the "locals examining hydrazine powered boosters" threads, I can't imagine many western nations willing to have nuclear plants built to Chinese regulations.

I don't know. SMRs are well underway in the development aspect.

And my nuclear electricity is pretty cheap (though likely subsidized).

[tater]

NTP is about I_sp. When we have operational heavy lifters, we can start comparing architectures, but for anyone who is skeptical about SpaceX Mars (or lunar) plans, you have to turn back to NASA, and their DRMs include an NTP option, and in the real world, with very, very limited launches with their only heavy lifter, SLS, they can't really count on assembling a large, multi-stage chemical rocket, since any such assembly literally adds one part per year.

[DDE]

6 hours ago, tater said:

NTP is about I_sp.

NTP is about ISP and decent thrust. Pure ISP favours NEP and SEP.

And the current panoply of Earth orbit commercial transports also favours electrics because, if those things could be augmented to reach a parking orbit beyond the rad belts, or even rendezvous in a near-hyperbolic orbit, you could live with the low accelerations and what Korolev called a podsadka scheme. Hell, Orion can catch an MTV at L1/L2.

Edited December 24, 2018 by DDE

[kerbiloid]

If humans can into Tesla tech (not the car on batteries, but true Tesla, with Wardenclyffe Tower, etc), they can leave the reactor stayng on ground, and have just a microwave receiver and a propelant tank on the rocket.

Like in KSPI-E now.

 

[0111narwhalz]

On 12/20/2018 at 6:40 AM, Ozymandias_the_Goat said:

At the same time, we have a long way to go before we even produce a functional terrestrial fusion reactor, so it’s not as if a fusion reactor is a near future technology. 

ITER is supposed to break net positive, and then some, starting 2025. We're probably only a couple of reactor generations from leaving "research" and going to "commercial proof of concept," at least for tokomaks. Stellarators have been sadly neglected until Wendelstein 7-X, but that reactor is breaking records left and right. Laser inertial confinement is also looking pretty good. It's always been "an exciting time" in fusion research, but right now it might actually be exciting.

And who knows what's going on with polywells.