New Nuclear Engine Concept Could Help Realize 3-Month Trips To Mars (newatlas.com) 131
Seattle-based Ultra Safe Nuclear Technologies (USNC-Tech) has developed a concept for a new Nuclear Thermal Propulsion (NTP) engine that they claim is safer and more reliable than previous NTP designs and with far greater efficiency than a chemical rocket. The concept could reduce Earth-Mars travel time to just three months. New Atlas reports: According to Dr. Michael Eades, principal engineer at USNC-Tech, the new concept engine is more reliable than previous NTP designs and can produce twice the specific impulse of a chemical rocket. Specific impulse is a measure of a rocket's efficiency. To fuel the concept, UNSC-Tech uses a Fully Ceramic Micro-encapsulated (FCM) fuel to power the engine's reactor. This fuel is based on High-Assay Low Enriched Uranium (HALEU), which is derived from reprocessed civilian nuclear fuel and is enriched to between 5 and 20 percent -- greater than that of civilian reactors and less than that of naval reactors. The fuel is then encapsulated into particles coated with zirconium carbide (ZrC).
The company claims that this fuel is much more rugged than conventional nuclear fuels and can operate at high temperatures. This produces safer reactor designs and a high thrust and specific impulse that could previously only be obtained with highly-enriched uranium. In addition, such fuel can be produced with current supply chains and manufacturing plants. It is hoped the new concept could lead to nuclear engines that reduce deep space mission times drastically, with a crewed mission to Mars arriving in as little as three months. Beyond that, the concept is aimed at a commercial market as well as with NASA and the US Department of Defense, allowing for more ambitious private missions.
The company claims that this fuel is much more rugged than conventional nuclear fuels and can operate at high temperatures. This produces safer reactor designs and a high thrust and specific impulse that could previously only be obtained with highly-enriched uranium. In addition, such fuel can be produced with current supply chains and manufacturing plants. It is hoped the new concept could lead to nuclear engines that reduce deep space mission times drastically, with a crewed mission to Mars arriving in as little as three months. Beyond that, the concept is aimed at a commercial market as well as with NASA and the US Department of Defense, allowing for more ambitious private missions.
Sounds promising (Score:2)
Re:Sounds promising (Score:5, Interesting)
Nuclear thermal rockets [wikipedia.org] are designed to use liquid hydrogen as a fuel.
Zirconium carbide has a melting point of 3800K.
H2 burning with pure LOX has a flame temperature of about 3300K.
But the exhaust velocity of H2 will be much higher than the H2O from combustion.
The exhaust would not be radioactive.
I don't think this rocket would be used for launching from the earth's surface. More likely, it will handle the LEO to LMO leg of the journey by shuttling between the planets. To handle surface-to-orbit, it would need a huge amount of power that would make it way over-engineered for the rest of the journey.
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That all depends on where the fuel is coming from.
If you are mining ice on the moon, then sure, you might as well use it all. It is cheap to launch with linear mass drivers.
But if you are hauling LOX up from the earth's surface, that is not going to be cost-effective. Better to go with just H2.
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Actually, getting LOX from the moon is liable to be far easier (or at least more abundant) than hydrogen from trace ice deposits - lunar regolith is 42% oxygen by mass, you just need to refine it from the oxides - whose other components are themselves valuable resources for the next stage of space industrialization. Mostly silicon, which probably isn't particularly useful right away, but also lots of iron, calcium, aluminum, and magnesium.
Dynetics (the company behind the low-slung "rabbit ear" Artemis moon
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It's impractical, though. Rather than a solid core NTR, a LANTR should give you much better mass parameters (higher propellant density), as well as better ISRU economy (you don't have to throw away 89% of your water, and you need less water to achieve the same propulsive effect).
Impractical? An odd objection when the proposed "practical" alternative in LANTR - "LOX-augmented Nuclear Thermal Rocket" - which combines the cost and complexity of developing a deploying a nuclear thermal rocket with the cost and complexity of building a lunar fuel factory to extract oxygen from lunar rock.
Producing oxygen on the Moon from regolith requires a complex entirely robotic mechanical and chemical system involving mining to dig up and crush ore, concentrating the titanium oxide component, a flui
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Or, you could use Sadoway's NASA-funded electrometallurgical process to extract oxygen and steel directly from molten lunar regoltih.
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Impractical? An odd objection when the proposed "practical" alternative in LANTR - "LOX-augmented Nuclear Thermal Rocket" - which combines the cost and complexity of developing a deploying a nuclear thermal rocket with the cost and complexity of building a lunar fuel factory to extract oxygen from lunar rock.
Yes, because thje NTR would magically conjure hydrogen on lunar surface out of nothing.
Or you could just bring the oxygen up from an Earth-side plant in a reusable two stage rocket system like Starship.
In the beginning, you could. In the end, this is not what you'll be doing. Why waste most of Starship's payload capacity on oxidizer for the return trip if a single landing can land 100 tonnes of ISRU hardware? Sooner or later you *will* be extracting that oxygen. Suddenly you'll need a fraction of Earth launches for the same useful traffic between Earth and Moon.
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With such high temperatures such an engine might not last very long before needing to be replaced. It's not just the heat, it's the thermal cycling over thousands of degrees.
Re: Sounds promising (Score:5, Interesting)
These types of engines have been shown to handle the heat just fine: https://en.m.wikipedia.org/wik... [wikipedia.org]
What's so exciting about this engine is the use of low grade uranium.
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What's so exciting about this engine is the use of low grade uranium
Not quite. From the article. Emphasis mine.
... is derived from reprocessed civilian nuclear fuel and is enriched to between 5 and 20 percent -- greater than that of civilian reactors
They are reprocessing spent commercial grade nuclear fuel*, which the USA should be doing anyway, and then adding enough fissile isotopes like Pu-239, U-235 or U-233 to allow the fuel able to provide a self sustaining fission reaction at the needed power densities. And making it more enriched than what is used currently used in commercial nuclear plants.
* Spent fuel rods are usually 96% U-238, 3% neutron poisoning isotopes or non fissile/fertile elements, and 1%
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Nuclear thermal rockets [wikipedia.org] are designed to use liquid hydrogen as a fuel.
They could also use water or methane as a propellant. This would have no advantage over chemical rockets leaving earth, but would be handy for the return trip, as those chemicals are far more easily found on other planets. So hydrogen to get to Mars, and fill up there with water or manufactured methane for the return journey.
Re: Sounds promising (Score:2)
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Actually, speed is the huge advantage over chemical rockets.
I was talking about a hypothetical water-propellant NTP, which would have no such advantage.
And plenty of H2O on mar to convert into H2.
I'm no chemist, but I believe that producing, storing and loading cryogenic H2 on Mars would be far more challenging than methane and oxygen, or water.
So my suggestion, probably not very practical, was to use water for a slow unmanned return trip.
Re: Sounds promising (Score:2)
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You don't burn it. You heat it up and expel it.
Yes, I know that. I mentioned H2+LOX combustion only as a comparison. Sorry for not making that clear.
Re:Sounds promising (Score:4, Interesting)
Well... ... actually the most practical nuclear thermal designs do burn it. ;) One of the biggest problems that old-school NTR designs had was a poor thrust to weight ratio. But you can have an "afterburner" with a nuclear thermal rocket, where you have small LOX tanks that burn with the (already nuclear-heated) hydrogen and vastly increase the thrust at liftoff (while still having a significantly higher ISP than a cold LH/LOX rocket). Liftoff is of course where you need thrust the most. The LOX tanks then run dry when you approach Max-Q, leading to a natural throttleback, where you then continue to orbit on purely nuclear-heated hydrogen.
There's all sorts of nuclear thermal designs out there, various airbreathing (with or without compressors), air augmented, etc designs - some of which even have the capacity for indefinite atmospheric flight or even hover. Not even getting into the diversity of designs for heating the hydrogen itself. The ultimate design would be heating the hydrogen with a "nuclear lightbulb" or a fission fragment design, so that you can heat the working fluid far hotter than the surface of your reactor itself (which needs to not only "not melt", but also retain structural integrity). But such concepts are very immature.
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Liftoff is of course where you need thrust the most.
Which is why you design it to be modular and build it in space.
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Surely they wouldn't use it for launch, but rather for the journey once they've left Earth's orbit, right?
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Surely they wouldn't use it for launch, but rather for the journey once they've left Earth's orbit, right?
Not for "launch" as in the booster, but nuclear thermal rockets could make a good second stage. However, as you say, LEO to moon/mars/etc transfer is where the high specific impulse of NTP really shines.
Note that the benefit comes not from the high energy density of nuclear fuel, but from the low molecular mass of the exhaust propellant (hydrogen) compared to the H2O and CO2 exhaust of chemical rockets.
Re:Sounds promising (Score:4, Insightful)
Note that the benefit comes not from the high energy density of nuclear fuel
Nonsense. That's a huge part of it.
Sure that isn't what makes it the way to defeat the tyranny of the rocket equation, but it is what makes it valid as a long-range continuous thrust rocket.
The reason for its high specific impulse is its high exhaust energy, not its low molecular mass, though of course those are intimately related with regard to the transfer of the thermal energy from the nuclear reaction to the propellant.
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He tried to argue that the energy density had nothing to do with the advantage of NTP engines, which is pure fucking nonsense.
As for launch, even then- nuclear-thermal propulsion *is* the answer for the tyranny of the rocket equation, just not yet. Not until, as you noted, weight can be reduced, or thrust increased.
Energy density of fission fuel vs. chemical is 2 orders of magnitude apart. They're not even in the same bal
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He tried to argue that the energy density had nothing to do with the advantage of NTP engines, which is pure fucking nonsense.
Not quite unrelated, just misses the point. (And profanity is the last refuge of the inarticulate motherfucker. )
The key measure of a rocket (for a given payload) is delta-V.
And we know from the rocket equation that delta-V is proportional to exhaust velocity, right? Which is proportional to the square root of (Temperature/molecular mass). OK?
You might think that NTP, with more "power" can have a higher temperature, but that is not the case in the real world with real materials.
It is in fact the second
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And profanity is the last refuge of the inarticulate motherfucker.
That's like, your opinion, man. ;)
You might think that NTP, with more "power" can have a higher temperature, but that is not the case in the real world with real materials. It is in fact the second part that matters, the molecular mass. (Same comparing RP1 to hydrogen.)
No, I don't think that in the slightest.
More power is capable of making *more* propellant a certain temperature per unit of fuel mass.
And again, it is not the molecular mass that matters.
Specific impulse cares not a tit about molecular mass.
Thermal expansion does, sure, but again- molecular mass is what provides the high kinetic energy- and again, only for thermal expansion. Which I granted you in our other discussion.
I almost think we must be getting confused in thi
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Specific impulse cares not a tit about molecular mass.
Here is the equation: Ve = k(T/m)^0.5 that is SI is inversely proportional to the root of the molecular mass.
Sounds like more than a tit to me.
This is what matters. Where in that equation does energy density come in? All you need is enough energy to reach the desired T, which is limited by the rocket materials. Hope I am clear now.
For an ion-drive, we do not worry about that because we make T massive, but NTP rockets can not.
source: http://large.stanford.edu/cour... [stanford.edu]
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P.S. for theoretical ion drives, your point would be relevant, I'm only arguing with respect to NTP.
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Here is the equation: Ve = k(T/m)^0.5 that is SI is inversely proportional to the root of the molecular mass. Sounds like more than a tit to me.
We're discussing Isp, and you give me Ve.
You have thus confirmed my point, that by Isp, you mean Ve.
Isp cares only for mass flow rate. Period. The molecular mass is irrelevant. As I said, it's only relevant in the case of a specific type of energetic impulse- thermal expansion.
P.S. for theoretical ion drives, your point would be relevant, I'm only arguing with respect to NTP.
No. My point applies to *all* drives.
You are the one making a constraint.
Isp is not tied intrinsically to molecular mass *except* in the case of thermal expansion.
That statement:
The Isp of a rocket is depen
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I'll answer both here.
We're discussing Isp, and you give me Ve.
OK, I overestimated your background knowledge there. For a rocket (as opposed to a jet engine), they are the same thing.
https://www.google.com/search?... [google.com]
https://en.wikipedia.org/wiki/... [wikipedia.org]
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>More power is capable of making *more* propellant a certain temperature per unit of fuel mass.
But that's exactly the problem - if you need as much propellant as a chemical rocket doing the same job, you don't offer any advantage. The tyranny of the rocket equation is mitigated solely by the exit velocity of the propellant, which is related to temperature by* v_rms = sqrt(3RT/M) - basically, the lower the molecular mass, the faster it moves at the same temperature.
Propellant temperatures are already li
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Well, I suppose nuclear engines do have one other advantage - they can operate with a non-combustible monopropellant such as LOX, which would actually have a lower specific impulse than many chemical rockets (though the SpaceX Raptor will have an almost pure oxygen exhaust) but could use plentiful LOX refined from the moon, which only offers trace amounts of hydrogen and carbon that you might burn with it.
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But that's exactly the problem - if you need as much propellant as a chemical rocket doing the same job, you don't offer any advantage. The tyranny of the rocket equation is mitigated solely by the exit velocity of the propellant, which is related to temperature by* v_rms = sqrt(3RT/M) - basically, the lower the molecular mass, the faster it moves at the same temperature.
You're right, of course.
Quenda and I had so many tangents going that I managed to get myself confused.
Where energy density of the fuel matters is of course that massively higher exhaust velocities are possible.
The energy pumped into the hydrogen is a tiny fraction of the total possible output of the reactor, constrained only by the physical limits of the fuel cladding- which has improved by about 40% over the course of the technology's life.
It also allows for an overall eventually better mass fraction d
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Well I certainly can't disagree in principle. I think *right now* power density is not really a limiting factor, so increasing it won't yield short-term gains. However, if we start deploying technology that puts much higher power density in our hands as a side effect, then it does seem likely that we'll rapidly begin to figure out how to put all that extra power to work.
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Nuclear rockets waste ~95% of their power. Every inch you can put into the propellant is a higher specific impulse, and there's a lot to grab. It just isn't easy.
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The reason for its high specific impulse is its high exhaust energy,
Not energy but momentum. We need to break the earthly habit of thinking about energy. Specific impulse is the effective exhaust velocity. The low molecular mass means higher velocity (so higher Isp) at a given temperature, and rockets are limited by the temperature the materials can tolerate.
H2 with mass of 2 compared to H20 - 1/9 the mass, so 3 times the velocity to achieve the same temperature (average kinetic energy of molecules).
(CO2 of course is much worse)
1kg of H2 exhaust has 9 times the energ
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Not energy but momentum. We need to break the earthly habit of thinking about energy. Specific impulse is the effective exhaust velocity. The low molecular mass means higher velocity (so higher Isp) at a given temperature, and rockets are limited by the temperature the materials can tolerate.
No, I meant energy- as in kinetic energy. But momentum works too.
The point was that the low molecular mass is what allows it to have high velocity (and kinetic energy), but the specific impulse does not specifically favor low molecular mass propellants. In fact, ion engines use the heaviest thing they can reasonably accelerate.
I will grant you, that in the specific case of an thermal rocket, we're going to favor the lightest exhaust gas we can use.
H2 with mass of 2 compared to H20 - 1/9 the mass, so 3 times the velocity to achieve the same temperature (average kinetic energy of molecules). (CO2 of course is much worse)
Yup, I understand the concept just fine.
1kg of H2 exhaust has 9 times the energy of 1kg of steam, but the important number is the momentum per kg, i.e. the velocity. It does not matter if that steam is generated by a chemical reaction, or from a nuclear boiler: the specific impulse is the same, and 1/3 that of H2.
Yup, I understand
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The point was that the low molecular mass is what allows it to have high velocity (and kinetic energy), but the specific impulse does not specifically favor low molecular mass propellants.
But Isp and Ve are the same thing. The qualifier is "at the same temperature", in which case molecular mass is everything. Any introductory tutorial on NTP will tell you this. And with current technology, NTP does not allow higher temp. (actually it is lower than chemical).
In fact, ion engines
That is a completely different topic, not relevant, and this is complicated enough already. Please lets stick to topic at hand: NTP vs chemical.
I will grant you, that in the specific case of an thermal rocket, we're going to favor the lightest exhaust gas we can use.
So no argument?
Here's where we transition away from the specific impulse of the motor and on to the other advantages. Fuel energy density.
That does apply to ion drives, but not NTP. Doubling or halving the energy
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But Isp and Ve are the same thing. The qualifier is "at the same temperature", in which case molecular mass is everything. Any introductory tutorial on NTP will tell you this. And with current technology, NTP does not allow higher temp. (actually it is lower than chemical).
Yes. The qualifier that you missed is "at the same temperature"
We are now in aggreance.
That is a completely different topic, not relevant, and this is complicated enough already. Please lets stick to topic at hand: NTP vs chemical.
It's completely relevant, as it's an explanation for the following claim:
"The reason for its high specific impulse is its high exhaust energy, not its low molecular mass, though of course those are intimately related with regard to the transfer of the thermal energy from the nuclear reaction to the propellant."
It's high specific impulse is because of its high exhaust energy. The fact that that results from low molecula
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Halving the energy density of a NERVA requires twice as much fuel to accelerate mass reaction mass mR.
No, because a NERVA only uses a small fraction of its energy before running out of propellant.
You, at this point, are essentially making an argument that can be summed up as this: There is no advantage to air-breathing engines, because carrying oxidizer is free.
So ya. Fucking nonsense.
I'm sorry you cannot make sense of it. But Ryan Hamerly explains it much better than I attempted to:
http://large.stanford.edu/cour... [stanford.edu]
Re: Sounds promising (Score:2)
And you don't understand the issue. Say you have 1 kg of reaction mass. You have some means of heating this reaction mass to 3000 degrees. The means of heating is irrelevant. It can be chemical, it can be nuclear, it can be magic pixies. It doesn't matter. It's just that you can heat the reaction mass to some given temperature.
Now look at how fast the reaction mass moves based upon weight. Hydrogen molecules have 1/9 the mass of water molecules. So at a given temperature, they're traveling 3 times faster. S
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In a rocket, you'd much rather carry more vee around than more em.
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Pinot Grand Fenwick!
Re: Sounds promising (Score:4, Informative)
https://en.m.wikipedia.org/wik... [wikipedia.org]
The pellets don't contain reaction mass, and this or similar engines will only be used once already in orbit.
Great except the public is wussified (Score:2)
If the public wasnt wussified we could have vehicles that run of plutonium RTGs that don't need replacing or refueling for 100 years. I mean, the 75 watt, 4 pound SNAP-27 RTG on the moon is still at 90% of its power. You get a 100 of those that's all you need for a never-refuel, never-charge automobile. Wrap it in gold or lead if you're scared of it.
Re:Great except the public is wussified (Score:4, Informative)
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Your weights are wrong, [wikipedia.org] and I think you're underestimating the power required to move a car at reasonable speed.
The SNAP-27 contained 3.8 kg of plutonium and weighed about 20 kg in total. Your hypothetical "never-charge" car would have a 2000 kg (4400 lb) battery to generate just 7500 watts. That's about 10 mechanical horsepower. For comparison, a Tesla Model 3 weights 3500-4100 lbs all-in, and puts out several hundred horsepower.
Re: Great except the public is wussified (Score:2)
Ok, youâ(TM)re right â" I should have known the 4 pounds was too good be true. Though, even a 10hp car that can drive around continuously if needed and never needs refueling is somewhat appealing.
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Though, even a 10hp car that can drive around continuously if needed and never needs refueling is somewhat appealing.
If it had enough power to get itself moving in less than 10 minutes, and the ability to climb a 5 degree incline, I agree... but it wouldn't.
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I was kind of thinking along the same lines, an RTG that's just an always-on battery charger where the batteries did the motive work. If the typical commute is an hour per day with maybe an extra hour of driving, that's 18 hours or 1.3kw of power restored without any plug-in and with a single 75w RTG.
For some limited use cases, the car may never be plugged in or only 1-2 times per month. Heavy daily drivers might not get much benefit, but I think something on the order of a 150 watt RTG would be a noticea
The future will be nuclear powered. (Score:5, Insightful)
If humanity is going to colonize the solar system then it's going to take energy sources with greater energy return than wind and solar, and more plentiful than hydro or geothermal.
Getting to Mars is one thing, surviving there is another. People that explore Mars will need energy for heat, light, air, water, food, and to produce the fuel for a return to Earth. There's no wind of any real substance on Mars. There are no rivers to dam. The planet doesn't appear to have much heat in the core like Earth to draw power from. In the unlikely event of finding any coal or petroleum there's the problem of no air to burn it with. There's some solar power available on Mars but by being much further from the sun than Earth means it is far more dilute.
Missions to Mars will be bringing nuclear power with them. Research on this will benefit us here on Earth since if there's a nuclear power plant that works on Mars then it will work on Earth.
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If humanity is going to colonize the solar system then it's going to take energy sources ...
Sorry, but you really do not understand the point of nuclear rockets. (Or you are totally off-topic)
It has nothing to do with "energy sources", but rather the Rocket Equation. [wikipedia.org]
Nuclear Thermal Rockets achieve higher efficiency than chemical rockets only because the exhaust gas, H2, is lighter, and therefore faster at the same temperature.
Electrical power generation for a colony is a totally separate question.
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Sorry, but you really do not understand the point of nuclear rockets. (Or you are totally off-topic)
The point of nuclear rockets is that they have a far greater energy density than chemical rockets. Chemical rockets produce more power, and so they will continue to be used to get from the surface of Earth to the Karman line. It's the energy density of nuclear fission that will allow us to get to Mars. This is not just valuable in providing the propulsion but also other energy needs.
It has nothing to do with "energy sources", but rather the Rocket Equation.
Indeed, it's because of the rocket equation that energy density is so important. This includes the mass needed to supply t
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The point of nuclear rockets is that they have a far greater energy density than chemical rockets.
Nope. This is a common error, at least for the type of rocket we have here, the nuclear thermal rocket.
For cars, we talk about energy efficiency and energy density of gasoline vs lithium-ion.
But rocket science is far removed from such common sense notions. Instead of power we want to know thrust. Instead of miles-per-gallon we have specific impulse.
Instead of energy we have delta-V. We talk about velocity and momentum, not energy as we do for earthly transport.
Take some time to read up and underst
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Nope. This is a common error, at least for the type of rocket we have here, the nuclear thermal rocket.
I don't believe it is an error. All those concepts are related and energy density is certainly part of it. It's not like velocity and momentum are uncoupled from kinetic energy.
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I don't believe it is an error.
Well, I guess it *is* rocket science. It took me a while to get :-)
You have to do the maths to understand. No calculus needed though.
You will then see the important factors in the equations.
There is a good primer here:
http://large.stanford.edu/cour... [stanford.edu]
I will just quote one passage:
There is another, simpler way to arrive at this factor of two. The velocity of the rocket propellant scales as vex ~ (T/m)1/2, where T is the propellant temperature and m is its molecular mass. In a chemical hydrogen-oxygen rocket, T ~ 6000 K and m = 18 amu. For a nuclear rocket, the temperature is halved (T ~ 3000 K), but the mass drops by a factor of nine (m = 2 amu), so the quotient increases by about a factor of four, doubling the exhaust speed.
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From the article you quoted:
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From the article you quoted:
Keep reading. The obvious is not always practical. And remember we are talking only about *thermal* rockets.
(for electric ion-drives, then hell-yeah we want as much energy as possible, though solar-panels are also an option)
This raises the maximum exhaust velocity to around 5,000 km/s. However, ...
So "obviously" a nuclear reactor could send super-hot plasma out the back, right? But no, not in the "New Nuclear Engine Concept" here.
It actually has a lower temperature than chemical. It makes up for that with the low molecular mass.
It seems people just assume the nuclear rocket ha
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Youtube tl;dr answer for millenials :-)
https://youtu.be/CizKnuwvXXg?t... [youtu.be]
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Yes, it is an common error.
And this threat is full with clarifications already.
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Fission reactors are probably not suitable for Mars because, as you point out, there are no large bodies of water to provide cooling. The whole system would have to be self contained, which means an RTG. Limited power output, not worth the effort on Earth where you can just build windmills at a fraction of the cost.
Oh sure there are some self contained fission designs but none actually proven to work or be safe yet. I wouldn't hold your breath on that front.
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Fission reactors are probably not suitable for Mars because, as you point out, there are no large bodies of water to provide cooling. ...
Oh sure there are some self contained fission designs but none actually proven to work or be safe yet. I wouldn't hold your breath on that front.
No need to hold your breath. Such reactors were built way back in the 1960s and flown in space, which is more challenging than Mars.
https://en.wikipedia.org/wiki/... [wikipedia.org]
The fission reactors proposed for Mars are small enough to be cooled by large radiators. At 10kW electrical, it is enough to get through the night, or survive dust storms. Higher power would come from solar panels in the daytime.
https://www.nasa.gov/press-rel... [nasa.gov]
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Oh sure there are some self contained fission designs but none actually proven to work or be safe yet. I wouldn't hold your breath on that front.
BS, they have been tested and they do work (as long ago as the late 1960s). And I know you know that because I've told you that personally before.
However, for the near future, its probably far more practical to use RTGs in space. Nuclear reactors are heavy and don't do well being dropped from orbit.
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There's no wind of any real substance on Mars. There are no rivers to dam.
Absurd. The Martian got marooned due to a sandstorm, and that was promised to be a very scientifically accurate movie. Also, canals have been observed on Mars since the late 1800s.
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There's no wind of any real substance on Mars. There are no rivers to dam.
Absurd. The Martian got marooned due to a sandstorm, and that was promised to be a very scientifically accurate movie. Also, canals have been observed on Mars since the late 1800s.
I hope you are joking. The air pressure on Mars is so low that even a Tornado wouldn't do any damage (and it certainly wouldn't tip over a huge rocket). However, the rest of the movie is fairly scientifically accurate. Fun fact, the writers of the movie wanted to have the RTG fail but two problems: 1) they couldn't figure out how the RTG would fail and 2) if the RTG did fail, they couldn't figure out a way that Mark wouldn't die.
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You forgot to mention radiation from space. There's no van Allen belts, and the Sun really doesn't like humans.
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You forgot to mention radiation from space. There's no van Allen belts, and the Sun really doesn't like humans.
NASA has a plan for that :-)
https://phys.org/news/2017-03-... [phys.org]
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The best 'colonize' mars idea I have seen is if we can figure out how to make use nukes to turn several tons of metal into a micro black hole and drop it into mars. In less than 100 years the gravity of mars becomes concentrated so that on the surface you get about 1G, enough to get a real atmosphere going, and if the micro black hole spins you get a magnetic field to protect us from solar radiation.
The entire thing should last a couple million years before the black hole becomes dangerous to people on th
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If you think "number of deaths" is the relevant factor, you are so ignorant of the nuclear industry that it isn't worthwhile to bother with you.
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Nuclear is wildly dangerous.
Does it cause more deaths than the fuel source that is pumping carcinogens into the air at a rate of kilotons per second? No. It doesn't.
It kills 0 people, because it's fucking clean.
However- they have the capability to cause fucking drastic damage when a problem happens, and discussing contingencies for that is what it's important, not pretending like that scenario doesn't exist- or worse, conflating a stati
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Nice trojan horse there.
I suspect you don't really know what that means.
Did I feign defeat and offer myself as a gift to be brought into his camp to destroy him while he sleeps?
Was I perhaps an app he downloaded that took over his computer after that?
But I somehow doubt you are actually pro-nuclear.
Oh, I am. But that's ok- I have doubts about whether or not you have an IQ over 40.
You are either a total idiot or one of the most sophisticated trolls I have ever seen.
This wall of inane text isn't giving me a lot of confidence in your qualifications to judge either way.
The GP posted the standard deaths per watt-hour statistic that nuclear folks often use.
Oh, I see!
The fact that pro-nuclear/anti-nuclear are 2 sports teams that engage in standard part
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Everyone is ranting and raving about how much nuclear caused cancer there is only it's usually a type of cancer that is rather treatable. So again, deaths caused by nuclear are still ratehr relevant.
You missed the point. You're conflating ongoing damage to human beings due to inhaling carcinogens and other pulmonary irritants with the effects of a containment failure. You're brushing it under the rug with shit like the following:
Meanwhile people are living in Prypjat
This just isn't an argument for anything involving Nuclear Power. It's an argument that Ukrainians are tough motherfuckers.
I saw a clip from 2009 where they dug into some random soil and measured 310uSv/h on the fucking claw they used when they were done.
That's nowhere near
Silent "e" (Score:2)
Ya, until ... (Score:2)
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Yah, you gotta start living in reality.
How does it actually work? (Score:2)
What is the propellant? Does the reactor core somehow impart extra kinetic energy onto the propellenat? How does thermal heat I assume get converted to kinetic energy? Is it in the form of high energy neutrons or alpha particles that hit
Re:How does it actually work? (Score:5, Interesting)
The lighter the molecule, the more efficient the drive in terms of specific impulse, so there's really only one choice worth considering: Hydrogen. It's really not too far from a chemical rocket, except the energy source is nuclear rather than chemical: You pump hydrogen at high pressure into the chamber, the reactor heats that hydrogen up to the highest temperature your drive materials can stand, then it just flows through a nozzle where it expands to convert that high pressure and temperature into kinetic energy - it shoots out the back of the nozzle, and your ship goes forwards with corresponding momentum.
Re: How does it actually work? (Score:2)
It works just like the nuclear rockets designed, tested, and built to fly on Apollo 18 or 19:
https://en.m.wikipedia.org/wik... [wikipedia.org]
Its still chucking stuff backwards to go forwards (Score:2)
Until we come up with a propulsion method that doesn't rely on chucking non replacable matter out the back then human space travel will be stuck in the inner solar system. Yes perhaps I have watched too many Star Treks but even so, point still stands. However given the huge magnetic field of the sun I can't help wondering if something couldn't push back on that even if the force is small, because over time that small constant force can generate huge speeds.
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Do look up solar sails. They're not high acceleration, but the fuel is free and the acceleration continuous.
it's impossible to provide the potential energy of a change in orbit without _some_ energy source. And the strength of the Sun's "enormous magnetic field" at Earth orbit only averages 6 nano-Tesla. The Earth's magnetic field is approximately 60 microTesla around the magnetic poles, roughly 10,000 times as strong. The Sun's magnetic field may indeed be measurable at Earth orbit, but it it falls as the
Re:Its still chucking stuff backwards to go forwar (Score:4, Informative)
Sadly as far as we understand physics, momentum (or if picky, 4-momentum) is absolutely conserved even under very extreme conditions.
The idea of pushing back on something already in space (like the solar magnetic field) doesn't violate that, but the options are very limited. The solar magnetic field near earth's orbit is around 10 micro-gauss.and its very difficult to think of a way to generate any significant force from that. Remember that all magnets are dipoles, so the N and S poles will pull in opposite directions, and only see a force proportional to the variation in the Sun's field. (which will be tiny over any practical distance).
Solar wind, solar sails have been looked at and can work but the accelerations are extremely small.
No obvious alternative to throwing stuff backwards in order to move forwards
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What about doing the opposite of solar sails - generating an extremely strong light source on the ship and facing it backwards. Would that work?
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Yes, it works because the light has energy and therefore mass. There is a problem though: the momentum of an object is M *V. the kinetic energy is 0.5 * M * V^2. So for the same momentum, the faster the exhaust is moving, the more energy you need to drive it. Light is moving at C, so it takes a huge amount of energy to generate much thrust.
This is a problem for ion engines. even though their exhaust velocity is much less than light, maybe 50,000 M/S or something, it takes so much power to drive th
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Yes, it would.
It is called a photon drive.
Or you put a mirror at the end of the rocket, and beam a laser in it. But for that actually a solar sail would be better.
Not as good as it sounds... (Score:2)
Re:Not as good as it sounds... (Score:4, Insightful)
BUT, it could be great for travel between space stations. So have some spacestations floating above mars, and just shuttle between mars and the spacestation with smaller crafts (or even space elevators) and use bigger ships to travel between the spacestation and a spacestation near earth.. THAT's actually the future, having different spacecraft for different jobs..
So we should get cracking at building spacestations as soon as possible, having extra vehicles up in space and stations up in space also makes it easier to clean up the crap (and reuse the crap at specific stations which are up there for recycling purposes)... yes, it will take decades, but it's the future.. Just do it, instead of only theorizing about it and making computermodels..
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Double the specific impulse means double the delta-v for the same mass ratio. For Mars, orbit-to-orbit transfers like you describe take around triple the delta-v, so you actually end up needing a bigger spacecraft to carry the same payload. And then you need two additional spacecraft for loading and unloading at the origin and destination, which themselves need to be designed, built, tested, and maintained.
Orbit-to-orbit is the only option for destinations like asteroids no matter what your propulsion is, b
Enough faster than solaar sail? (Score:2)
Solar sails accelerate continuously, and can first sail towards the Sun to improve their efficiency and reduce trip time. An estimate of 400 days to Mars orbit seems consistent. If the rocket approach turns out to too expensive, especially to transfer the bulky life support systems and return vehicle a Mars mission would need.It could be the way to transfer most of the material. If the life suport can handle a 400 day trip, the solar sail might be used effectively for the mission itself.
How long a stay before the return becomes 6 months (Score:2)
Never trust an adjective in a name (Score:2)
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"Ultra Safe" immediately has me worried that they'll somehow create a nuclear accident worse than Chernobyl.
Nobody ever referred to Chernobyl as "Ultra Safe" or even "safe". Scientists and engineers were warning of the dangers of the RBMK in the 60s due to its positive void coefficient. I understand the cynicism and nuclear probably isn't so great in orbit but nuclear power is the safest form of power we have by a significant margin. Maybe you were thinking of the automotive industry where "Ultra Safe" doesn't mean that.
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Yeah FTG (Score:2)
https://www.youtube.com/watch?... [youtube.com]
Will the green legions allow it? (Score:2)
The Green movement has been virulently, dogmatically antinuclear for 50 years. So much so that at least a few probes have gone up that should have ideally been powered by RTGs but hysterical fear about "nuclear anything" made NASA switch to less ideal power systems.
Tug (Score:2)