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NASA Funds Designs for a Nuclear Thermal Propulsion Rocket (space.com)
"Dangerous radiation. Overstuffed pantries. Cabin fever. NASA could sidestep many of the impediments to a Mars mission if they could just get there faster," writes Space.com, which reports NASA is now exploring an alternative to chemical rockets.
In August, NASA announced an $18.8-million-dollar contract with nuclear company BWXT to design fuel and a reactor suitable for nuclear thermal propulsion (NTP), a rocket technology that could jumpstart a new era of space exploration. "The strengths with NTP are the ability to do the very fast round trip [to Mars], the ability to abort even if you're 2 to 3 months into the missions, the overall architectural robustness, and also the growth potential to even more advanced systems," Michael Houts, principal investigator for the NTP project at NASA's Marshall Space Flight Center, told Space.com. NTP rockets would pull all that off by offering about twice the bang for the buck that chemical rockets do... "Nuclear thermal propulsion can enable you to get to Mars faster, on the order of twice as fast," said Vishal Patel, a researcher involved in subcontract work for BWXT at the Ultra Safe Nuclear Corp. in Los Alamos, New Mexico. "We're looking at nice 3- to 4-month transit times."
You heat water or hydrogen (probably hydrogen,since it gives you a higher Isp at lower temps). And squirt it out the back...
"I do not agree with what you say, but I will defend to the death your right to say it"
Read up on Projext Orion and on Aircraft Nuclear Propulsion (both closed-loop and open-loop designs).
Extrapolate.
Profit.
For a split moment, I thought I’d just read: “Dangerous radiation. Overstuffed panties. Cabin fever.”
The point of the "nuclear" is you heat up the exhaust hotter than you can get by just burning fuel and oxidizer. Exhaust velocity (the Isp part of the rocket equation) goes like the square root of energy released per unit of fuel burned. That sets a point of diminishing returns on chemical rockets. You can get go faster if inject more energy into the exhaust, but not if that energy comes from more fuel you have to carry with you and burn. Nuclear gets you orders of magnitude more energy density that you can dump into the exhaust with effectively no penalty other than the weight of the reactor, which grows much more slowly than an equivalent weight of chemical fuel would. That said, ain't no one building anything to go into space for under 30 million. This is more like research. I'd be surprised if any metal gets cut for anything other than individual component bench testing. TRL 1 type stuff.
More like crib from NERVA, and per a friend of mine who's father was one of these, in the 1980s someone had the bright idea of gathering the surviving team members and getting an infodump from them. Click on the Project Timberwind link, that was likely how it happened, the timing is right.
As in Robert Heinlein's book The Rolling Stones, copyright 1952
That said, ain't no one building anything to go into space for under 30 million. This is more like research.
Even if a prototype went into space, it'd still be research. No humans? No hurry. The Moon? Too close. A nuclear powered SLS-class launcher to Mars could be useful, but it would obviously be many years and many billions from now. And even for Mars the radiation estimate for a six months trip + surface stay with chemical rockets is within NASAs career limits, so it doesn't seem to be a requirement. And past Mars there's not really anywhere habitable for humans. I suppose it could be useful for interstellar, but the distances are so vast that we'll likely invent fusion reactors that'll overtake them before we got there, even if that takes centuries.
Live today, because you never know what tomorrow brings
So, can I send this well-proven design?
It's about time NASA started making Buck Rogers type equipment. This going up and down and round and round was starting to get boring.
.....we need to destroy every star we come across, starting with the Sun. That way we can prevent more radiation from polluting the Universe.
"A nuclear powered ion-drive seems a lot more likely to work."
Indeed. Hydrogen is sort of stupid, but that is where they started decades back, and it is perhaps best if they continue along those lines and develop it properly. Then load up with Xenon and get serious. Get the Reactor nice and toasty, both heat and ionize the Xenon with it, and then work with what Plasma Physicists have been doing, in accelerating the product and shooting it out the back end. (Accelerators are notoriously thirsty, but that is another thing Reactors are good at providing.)
135Xe is a particularly good candidate, as it has a very high Thermal Neutron Cross Section, and can carry some of those pesky Neutrons away with them. It isn't stable of course, but it is again another one of those things that Reactors are good at producing.
The Physics is done; the rest is mere Engineering.
A very interesting Captcha: Borate. 10Bo also has possibilities along these lines.
TRL 1 type stuff.
Well, the Rover and Pee Wee projects built and tested nuclear rocket engines, so it's already beyond Technology Readiness Level (TRL) 1. Right now nuclear thermal rockets are TRL 4: Module and/or subsystem validation in laboratory environment; standalone prototype implementations.
The trick was to get them to TRL 5 and beyond.
Project Pluto as well.
That was a crazy idea - cruise missiles that could stay airborne for months spewing radiation along the countryside.
Nobody seems to care about the word "nuclear submarine" or "nuclear air craft carriers.". Nuclear powered submarines are proof that a nuclear reactor can be safely operated in a small and closed system. The same type of closed system you would find a space vehicle. The technology already exists so the only thing needed is to find the most fuel source.
Hydrogen has the advantage that it's available anywhere you can find frozen methane. Xenon can be a bit harder to scavenge. What I'd really like is a "high" power ion rocket that could use rocks for exhaust. This, though, is a big problem because rocks aren't a simple element, but a complex mix that varies. (By "high power" I'm thinking of about 30 pounds thrust, but that's probably dreaming.)
I think we've pushed this "anyone can grow up to be president" thing too far.
We can save weight by trading shielding for distance. Just use a long conductive tether to tow the reactor a km behind the main payload. The radiation will drop off as the square of the distance.
You can look these things up, Chris.
https://en.wikipedia.org/wiki/...
You're a loony. You've probably got a cat license too.
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
Material limits set what we can do with conventional rockets. Not just melting points but thermal shock and fatigue.
No. Chemical rockets are limited by the energy content of the chemical fuel. They haven't been limited by materials for well over fifty years.
Those material limits are the same for a nuclear power source - and shoving water through a barely sub-critical reactor to heat it seems like a laughable idea. Water is hellish corrosive at high temperatures so odds are you'd be leaving a trail of reactor guts behind you before the engine had been running long.
Nobody proposes using water as reaction mass in a nuclear thermal rocket-- Specific impulse (Isp) is not high enough; you might as well use chemical propellants.
Hydrogen isn't a lot better. See "hydrogen embrittlement"
Hydrogen is a lot better. It is pretty much what everybody (or at least, everybody who knows the technology) would use for a NTR.
Since nuclear engines were designed, built and tested with hydrogen reaction mass back in the 1960s and early 1970s, your belief that they couldn't work is quaint.
A nuclear powered ion-drive seems a lot more likely to work.
Yes...and no. Ion drives put out a very low thrust per unit power. Thermal rockets are high thrust. There are some applications where you can get there slowly but efficiently, but it's definitely an engineering trade-off.
"A nuclear powered ion-drive seems a lot more likely to work." Indeed. Hydrogen is sort of stupid, but that is where they started decades back, and it is perhaps best if they continue along those lines and develop it properly.
Yes, nuclear thermal is very simple, and it has been demonstrated.
Then load up with Xenon and get serious. Get the Reactor nice and toasty, both heat and ionize the Xenon with it, and then work with what Plasma Physicists have been doing, in accelerating the product and shooting it out the back end.
Really you want to do one or the other, not both. Either use the thermal energy, in which case you want hydrogen, or convert the thermal energy to electrical power and use an ion engine, but not both at once.
(Accelerators are notoriously thirsty, but that is another thing Reactors are good at providing.) 135Xe is a particularly good candidate, as it has a very high Thermal Neutron Cross Section, and can carry some of those pesky Neutrons away with them.
That makes little sense. If you're using the reaction mass for neutron shielding, basically you want the lowest atomic mass you can get. And a fuel that decays with a half life of 9 hours means you'd have to breed the fuel in situ.
Space is already a radiation blasted wasteland. Plus the hydrogen fuel of these designs arn't inside the reactor long enough to become radioactive (Nuclear Thermal Rockets are very different from Fission Fragment Rockets). While the NERVA didn't completely solve the problem of fuel erosion (meaning it's exhaust was somewhat radioactive), they were close to solving the problem when the program was cancelled in 1972, and we should be able to something better with 45years of progress in material sciences
Look up NERVA, NASA BUILT and TESTED Nuclear Thermal Reactors in the 60's and 70's, they were almost flight ready when the program was cancelled
Uh... this is hardly going to add anything to the already existing mountains of dangerous radiation in interplanetary space. The point is to get from Earth to Mars *faster* so that astronauts don't have to spend so much time in the radiation bath outside the magnetosphere.
We had this tech in the 60s. No Nukes in Space treaty killed that. An engine isn't a weapon.
No, it didn't. The Nuclear test ban treaty banned nuclear explosions in space. It didn't ban nuclear reactors, and in fact several have been flown (primarily in the old Soviet Union's RORSAT program, but one-- SNAP-10A—by the US.)
Nuclear thermal is particularly interesting for Venus ascent stages. It lets you do them single stage, and while you essentially have to use hydrogen, it doesn't take that much. It reduces the habitat lift requirements dramatically; while the dry mass is high, the vastly reduced propellant requirements outweigh that many times over. It aslo makes it plausible to launch to high elliptical orbits rather than LVO; this cuts the Dv requirements down on the interplanetary transfer stage significantly, meaning either faster transfers or larger payloads. Some NTR designs offer hover capability, which would enable (effectively) limitless, propellentless hover time during docking without needing a balloon stage. And lastly, since a Venus ascent stage would never operate anywhere even near Earth, NIMBY concerns would be greatly reduced.
The most exciting phrase to hear in science, the one that heralds new discoveries, is not âEureka!â(TM), but
Nuclear powered Ion engines (or Nuclear Electric Rockets) add the complexity of electrical power conversion and thermal management. NERVA ran at just under 5GW thermal power, however since the heat was carried away by the fuel, they are easy to keep cool. Powering an Ion engine with a nuclear reactor means you need to dump all the heat generated by the reactor using radiators. JIMO proposed a 200kW reactor and needed a football field sized radiator to keep it cool
Unfortunately (orrather fortunately) we'll almost certainly be sliding backwards on a a TRL perspective. There have been a lot of major improvements in NTR design since then - not just for higher peak ISPs, but in particular to deal with the poor T/W of previous designs. The first big improvement was the LOX afterburner concept, wherein you burn the hot hydrogen with LOX early in the flight fie greatly augmented thrust, then revert to pure H2. Since then a lot of designs have also called for bringing atmospheric air into the mix, ranging from simple ram air thrust augmentation all the way up to designs with nuclear thermal-driven compressors and NTR scramjets.
Its hard to say at what point the added complexity ceases to pay off, but at the very least, the afterburner offers a huge leap forward at little cost. And of course you want modern ISPs too. To a point ; some of the more exotic reactor designs can theoretically provide crazy ISPs, but they do so by keeping the hydrogen hotter than the rest of the reactor with tricks like fission fragment reactors, which are anything but mature. Then again, if the craft could also double as a pure fission fragment rocket as well, that would certainly be pretty keen...
The most exciting phrase to hear in science, the one that heralds new discoveries, is not âEureka!â(TM), but
That's all there is to it. The rector is very hot, you take hydrogen from your tank, run it through the reactor where it boils and heats up to however hot you can run your reactor (much hotter than hydrogen and oxygen burns), and let it flow through a nozzle. You'll need a pump to push the hydrogen into the reactor, but that will just be a turbopump running off some of the hot gas. You can then use the turbopump exhaust to keep the pressure up in your propellant tank.
Prediction for end of Universe #42: Fencepost error in Quantum_bogosort.cpp
That's kind of the point behind the very well thought out design of the space ship Discovery One in the film 2001: A Space Odyssey. You had a spherical pressure hull up front and a nuclear rocket in back with a long boom connecting/separating them, along with propellant tanks and other stores.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
You don't have to use xenon for your ion drive.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
As an extension, read up on every attempt to do this since the 1950s. Jeezus, they've been dreaming about this for sixty years and it's always just a decade or two away from being practical. This latest one isn't going to be any different.
Almost correct. The temperatures are not actually hotter than a chemical rocket, but you can use pure hydrogen as fuel. Since hydrogen molecules are lighter than typcal exhaust gasses (water, CO2 etc), at the same temperature they are moving faster. That means you need less mass for the same velocity change in the rocket, or you can go faster on the same fuel.
The best chemical fuels are around 4500 M/s exhaust velocity. Storable chemicals are more like 3000 M/s. Nuclear thermal rockets get to around 10,000M/s So in principal you can go 2X as fast with the same fuel to mass ratio.
There are lots of caveats. The reactor is heavy. The radiation shielding is heavy - these both mean that you need a very large spacecraft before you have a net win in performance.
You probably don't want to turn one of these on before you are in orbit due to the potential problems with an accident (and the thrust to weight is pretty small anyway).
An additional problem is that its difficult to store hydrogen for long periods of time - you would need a complex and heavy refrigeration system. Or you can just use the nuclear rocket for leaving earth, and conventional storable chemicals for arrival.
Its a reasonable idea but with a lot of engineering tradeoffs that need to be considered. Its .... rocket science.
Space is big. Really big. You may think its a long way to the chemist, but that's nothing to space.....Douglas Adams
Until you start up the reactor, you just have uranium fuel (half life about 1 billion years), not lots of nasty highly radioactive stuff. If it fails on launch and the fuel is not contained you only have chemical heavy metal toxicity to worry about. I expect they can do a good job of containing the fuel in any case.
Once the reactor starts up, you are safely in orbit. The biggest danger would be on return from Mars to Earth orbit. You'd certainly want to design these things not to ever attempt reentry. It would take a lot going wrong to cause accidental reentry.
I'd want there to be a high quality risk assessment, but I think it wouldn't be hard to reduce the risk of atmospheric contamination to very low levels.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
The one plan I ever saw for nuclear thermal (a paper by Von Braun outlining a Mars mission) was to use nuclear thermal as an upper stage. The reactor isn't turned on (and producing fission products, like Chernobyl and Fukishima) until everything was safely on an escape trajectory away from earth. In any kind of earthly accident scenario, the worst which could happen is to put only the initial radioactive fuel into the ecosphere. If that were Uranium-235, U235 isn't very radioactive with a half life of 700 million years, not much smaller than that of potassium-40 (1.2 billion years) which is everywhere naturally. K40 plus all the other background sources; a spacecraft reactor full of U235 spread around wouldn't make a sensible difference. That assumes that an accident would even break containment...
If you are going with a high specific impulse and also greater-than-micro thrust propulsion system, you will need some kind of thermodynamic cycle to generate the required electric power, and that cycle will need to reject heat. Furthermore, the heat rejection for the cold side of that cycle into vacuum involves Stefan-Boltzmann T^4 limited radiators -- the "radiator" in your aging apartment building benefits from convection of air that is not on option in space.
Even a photovoltaic cell is subject to the Carnot limit on efficiency. The solar cell has the advantage that the hot side is surface-of-the-Sun hot in terms of the radiation spectrum of the impinging light whereas you have large surface area of the panels to radiate from the cold side. However clumsy and bulky solar panels are, you will need something almost as clumsy and bulky for radiators for a nuclear energy cycle to generate electricity venturing farther out from the Sun.
Is Discovery a nuclear-electric craft? In the 2001 A Space Odyssey genre of science fiction, you still get to wave your hands a lot even though it was meant to portray a plausible near-term future rather than warp drives and Star Trek transporters. Early concepts of Discovery had large space radiators making it dragonfly-like in appearance, but that wasn't "cool" so it ended up with this thin spine with the habitat at one end and presumably the nuclear power plant way at the other end. I never did figure out what those "pods" or "bunkers" were along the spine -- too small for cryogenic propellant storage, too small for proper Stefan-Boltzman fourth-power-of-surface-temperature radiators.
There are crazy concepts for more effective space radiators involving spraying water or pellets to get enormous surface area and then somehow recapturing the water or solid pellets so you don't end up losing them. Discovery didn't seem to depict that system.
And then there is nuclear thermal, but those are much lower specific impulse, not that much better than chemical rockets, especially when you consider the bulk of liquid hydrogen tanks and the weight of the nuclear reactor. Your "radiator" (Carnot-cycle cold side) is to blast H2 molecules out your rocket nozzles, a lot of H2 molecules. We have come full circle from the NERVA project of the 60's to VASIMIR or whatever kind of much higher impulse nuclear or solar-electric propulsion back to nuclear thermal, again?
because you know what you are talking about.
I'm wondering if part of the impulse for doing this is that it would be nearly inconceivable for Space X to get the permitting to do this, while NASA being the government can get the government's permission to do this. Is this a push back against commercial space exploration?
sarcasm.
by TheSpoom (715771) Uncaring Linux user here. I have nothing to add to this but please continue. *munches popcorn*
While we're at it, why don't you work on ways to eradicate the biggest source of dangerous radiation in our solar system - the sun.
Uneducated environmentalists and like-minded Hollywood script writers have got you convinced that zero radiation is the natural state of things, and any radiation is aberrant. It's actually the other way around - radiation is everywhere. Even your own body is radioactive. The only reason the sun's radiation doesn't kill everything on Earth is because of its magnetic field, which directs most of the solar radiation into the polar regions (where it collides with air molecules and ionizes them to create the aurora, instead of ionizing your DNA and causing cancer and genetic defects). It's actually one of the biggest problems that need to be overcome for a manned Mars mission. Any additional radiation due to nuclear rockets will be negligible.
you're overestimating how much mass we can move to Mars by conventional rockets. We can't send the ISS to Mars, our biggest rocket can send 8 tons to Mars transfer orbit. We're going to send up 57 of those to push the ISS to Mars? thousands of them for your 100 year colony's supplies.
No, we need powered fusion rockets.
Even with that shielding effect of atmosphere and magnetic field, the Sun still kills a million people a year with radiation. Dangerous thing, that Sun.
Just curious what sort of pollution or fallout we can expect if the rocket carrying this into space (or the rocket itself, if it's going up itself) has a catastrophic incident? Is the nuclear fuel in one of these things going to make a big mess as it spreads through the atmosphere and falls into the ocean?
I thought the radiation they are talking about in the summary was from the sun.
Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
To put this in perspective, 30 million is 10% of the cost of an F-35 if i recall. 15x AIM-54 Phoenix missiles. a fraction of a single B2 or Aircraft carrier...
Flexible structures are tricky. Long structures are flexible. There is no free lunch.
And if I understand nuclear reactors correctly, a lot of that mass is necessary for the thing to work, not for shielding.
Gaseous core nuclear reactors are the future - RD-600M.
Solid core engines are too primitive. We are almost 60 years into a space age now
I stand to be corrected, but could a nuclear reactor provide huge amounts of electrical energy which combined with a massive ion drive create an interesting and efficient propulsion system? Very lay perspective here. Spitballing
What I'd really like is a "high" power ion rocket that could use rocks for exhaust. This, though, is a big problem because rocks aren't a simple element, but a complex mix that varies. (By "high power" I'm thinking of about 30 pounds thrust, but that's probably dreaming.)
You're looking for a mass driver. You sit your rock on top of a superconducting magnet and accelerate in a large EM cannon. When it's nearly at the end you let the rock fly on and decelerate the magnet for reuse. Exhaust velocity is as high as your power supply and the length of your cannon allows. Thrust depends on rate of fire.
Actually, an NTR CAN work for a first stage, and would be even better as a second stage.
The problem is that NIMBYs will have a fit.
And when it comes to acid, plenty of metals that can deal with it.
Finally, NTRs would be perfect for the moon. Just use H2 for the fuel and O2 for breathing.
Perfect.
I prefer the "u" in honour as it seems to be missing these days.
Even old (let alone modern) NTR rockets had quite positive T/W ratios on Earth - let alone Venus where gravity is lower. I don't know what type of rocket you're picturing, but it's not nuclear thermal.
1) The conditions on Venus are often overstated. There's only a few to a few dozen mg per m3 H2SO4 in Venus's "habitable zone". OSHA allows workers to breathe up to 1 mg per m3 for an entire 8 hour shift. Admittedly the acid mists on Venus are a higher concentration than on Earth, but it's important to realize that we're talking vog here, not an "acid bath"
2) Exposure to an acid VOG is nothing compared to the conditions inside an operating rocket engine in terms of corrosiveness.
The most exciting phrase to hear in science, the one that heralds new discoveries, is not âEureka!â(TM), but
huh,
That is clever adding the LOX to that, and then discard the tanks. Nice way to get up to speed quickly.
I prefer the "u" in honour as it seems to be missing these days.
Project Timberwind was a far more advanced system design than NERVA (although, unlike NERVA, they never built a prototype). The thrust-to-weight ratio of the NERVA engine was 1:1, for Timberwind it was 30:1. The notion that Timberwind is derived from NERVA does not stand up to the slightest bit of scrutiny. The designs are entirely different (other than, you know, both using a nuclear reactor and hydrogen propellant). Any new effort in this direction is likely to use Timberwind as a reference design for a jump-off point.
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
Why? It is not like the exhaust is radioactive.
However, a very small shielding, combined with a truss arrangement (lined with H2 tanks, radiators) would be superior.
I prefer the "u" in honour as it seems to be missing these days.
The reactor is heavy. The radiation shielding is heavy - these both mean that you need a very large spacecraft before you have a net win in performance.
You probably don't want to turn one of these on before you are in orbit due to the potential problems with an accident (and the thrust to weight is pretty small anyway).
An additional problem is that its difficult to store hydrogen for long periods of time - you would need a complex and heavy refrigeration system. Or you can just use the nuclear rocket for leaving earth, and conventional storable chemicals for arrival.
Its a reasonable idea but with a lot of engineering tradeoffs that need to be considered. Its .... rocket science.
NERVA was heavy, but it was a primitive design. The Timberwind reference design is not heavy, it has an impressive 30:1 thrust to weight ratio. The shielding problem is much less than you think. Until you consume nearly all of your fuel, it provides lots of shielding, and the nuclear-thermal propulsion systems are high thrust, short burn time systems. The crew would enter a small shielded shelter during the five minutes or so of the final arrival "burn". And of course, your stores (food, water) would be arranged for free shielding.
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
Why doesn't NASA just contract Taco Bell to supply all the inflight meals? Much cheaper and no gamma rays.
How naive you are.
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
Even if you don't discard the LOX tanks and do it as a SSTO, the mass fraction is still greatly improved versus a pure hydrogen NTR. And even in the portion of the flight where you're burning LOX with the hot H2, it's significantly higher performance than a regular hydrolox engine, because the hydrogen has already taken on a lot of energy; if I recall the numbers correctly, designs predict somewhere around 550 sec sea level.
Adding an afterburner doesn't increase the total system mass much, but greatly increases thrust for early in the flight when you really need it. And in many ways, you're facing a much easier task than a regular hydrolox engine. Your hydrogen is gaseous and has enough energy to vaporize the LOX, so you're dealing with gas phase combustion, as well as self ignition.
It's interesting thinking about how far you can take nuclear thermal designs. Picture, for example, the afterburner case, with a fission fragment reactor as the heater. You can transition all the way from super high thrust for liftoff and atmospheric flight, to moderate thrust / high ISP for attaining orbit and performing orbital maneuvers, all the way to ISPs in the hundreds of thousands via direct fission fragment propulsion (note: requires large radiators). A single system could provide you access to every flight mode needed for missions ranging from the surface Earth out to the Oort Cloud and even potentially beyond - as well as effectively unlimited onboard power. And you can refill it anywhere you can get water; given the very high temperatures capable in the core, the primary loop should readily function for thermolysis (it happens on its own at those temperatures), with hydrogen-selective membranes leading to the hydrogen tank and a chiller for liquefaction (needed regardless to deal with boiloff).
The most exciting phrase to hear in science, the one that heralds new discoveries, is not âEureka!â(TM), but
In his "What's New" column for the week of December 20, 1996, PhD. physicist Bob Parks writes, "But an NRC study released this week also looks at the long-term exposure to cosmic radiation. It estimates that during a round-trip to Mars, the nucleus of every cell in the body would be traversed by a primary high-Z, high-energy particle. Nobody is certain about what that would do, but it's not likely to be good for you."
If you reduce the round-trip time for a Mars journey by one-half, does that mean only half the cells in your body are traversed by a high-Z (i.e., high mass) particle? We are 21 years past Bob's article. Do we now know the results of the postulated cell damage?
Circle the wagons and fire inward. Entropy increases without bounds.
Just huck all the mass into the converter and fire away.
Developing a nuclear reactor suitable for space flight would be a game changer, assuming it could be scaled to megawatt levels.
1. Power a magnetic shield.
2. Powering Ion drives for longer journeys
3. Of course providing all the electrical power for communications and other ship functions regardless of the distance from the sun
You get megawatts of power available and suddenly, you are talking about building a ship, not a tin can.
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
We're going to need some pretty major advances before we can reach even 1% of lightspeed for a craft of any significant size, thanks mainly to the exponential demands of the rocket equation. I rather suspect that comparing today's most advanced theoretical nuclear rocket designs to the first rockets to reach 10% of lightspeed will look rather like comparing an ancient aeolipile to a modern steam engine.
And we might still never see such speeds within the solar system, especially for human use. Even accelerating at a constant 10g it would take about 83 hours to reach 10% of lightspeed, at which point you would have traveled 4,500 Gm, or roughly to the orbit of Neptune. Great for exploring the Oort cloud, and adequate for traveling to nearby stars (assuming you've solved the other challenges). Of course, keeping your passengers alive under that sort of acceleration presents it's own challenges. (Though there are some interesting techniques out there for applying uniform accelerations, i.e. "free fall", to living organisms)
--- Most topics have many sides worth arguing, allow me to take one opposite you.
What I understand is that the main problem with Project Orion was radiation exposure on the ground. For a Mars mission, might it be possible to send the nuclear propulsion system up in pieces on conventional rockets, assemble them in space, and then let loose with the nukes when you are clear of Earth?
Even project Orion doesn't get you to 10% of lightspeed -- there isn't that much energy in plutonium at any even slightly reasonable mass ration.
You need an efficient fusion rocket or antimatter to get a rocket up to that speed, especially if you want to stop again. More plausible are beam-rider designs where the "engine" is left at home.
Will the rocket have a DVD player for the kids? Otherwise, it is 2-3 months of, "Are we there yet?"
In space, you have nothing to use. Many of the quoted nuclear projects still require carrying an exhaustible, explosive, material (eg oxygen, water, hydrogen) when the real goal of a space craft is propulsion by the nuclear reaction itself, with no other materials.
Of course you need reaction mass, so unless your design is one where the reactor fuel itself is spat out the back (NSWR, fission fragment, ...), yeah, you need reaction mass. You're not talking about nonsense reactionless drives are you? This is the real world, where we need reactions.
We are not at a stage in spaceflight that allows us to rescue a space craft. The shuttles are out of commission.
Why is the Space Shuttle required to perform a rescue operation? Actually, why would you use the Space Shuttle to perform a rescue operation? That thing only had a few hundred m/s of maneuverability once it made orbit.
Though I will say they've got their NERVA....
Should we assume that, at the very least, they're going to start with that, rather than from scratch?
Until we build cheap SHLV, such as SpaceX's BFR/BFS or Blue Origin's New Armstrong, it makes little sense to send supplies to Mars. What does makes sense is to send robotics to the moon via FH, to explore both lave tubes and craters. From there, we can establish where to build a base, so that we can fly more FHs, followed by BFRs and NAs.
I prefer the "u" in honour as it seems to be missing these days.
Relax, BWXT will be working on multiple designs. I would be surprised if one of them is NOT thorium since it is easier to come by than Uranium/Plutonium.
I prefer the "u" in honour as it seems to be missing these days.
Mars is not massive enough to hold an atmosphere we could breathe and live in without external support. You may as well colonize the moon. Also, it's closer, conveniently. Mars is an uninteresting and uninhabitable ball of rock.
THAT SAID, if you MUST go, why not just give every member of the crew a medically induced coma, a catheter, external electronic stimulation to keep muscles from atrophy, IV nutrition and hydration, etc.
The crew and colonists would launch to space, be hooked up to machines and knocked out, to be awakened just before arrival, (or if you're confident nothing would go wrong with all the vibration of a rocket-launch, they could sleep all the way from before launch to after landing). This is how launch-day could go.
7AM, wake up to last day on earth. Have coffee, clear out of hotel room.
8AM, remember NOT TO EAT breakfast.
9AM, report for lift-off.
10AM, LIFTOFF, orbit, verify all systems are go.
11AM, all passengers load into transit pods.
12PM, passengers are all rendered comatose.
1PM, crew oversees initiation of long, slow burn to change to Mars orbit and catch planet.
2PM, crew all load each other/selves into pods, and are rendered comatose.
--months later--
zero hour (h=0): first of crew reawakened by onboard computer.
h+1, first crew member checks over craft and crew, begins waking rest of crew; verification of location & velocity, plus trajectory. Supply craft sent to land on Mars. Reports sent to Earth.
h+2, crew now awake and undergo health checks; crew gets ready to wake passengers, perform health checks on them, etc.
h+3, passengers all awake, undergoing checks of status, health, etc. All supply craft are verified as having landed safely on Mars.
h+4, passengers board landing craft.
h+5, passenger landing craft, sent from interplanetary transit module, lands on Mars
From the point of view of the passenger, the duration between 12 PM on take-off day, and h+3 several months later, are seemingly only about an hour apart. For most of the crew, that day is only a few hours longer, despite it having a months-long "..." in the middle.
If you ARE going to be stupid enough to try to colonize a rock that will never be able to see your descendants walking around on the surface, without the aid of life-preserving space-suits, THIS is the way to do it. No advanced engine required.
To be clear, we have ALL the technology needed to put humans on Mars now, and it wouldn't be at all even difficult to do. There's just no reason to do so. Ever.
Our reign has gone on long enough. Indeed. Summon the meteors.
The only way you get to where "Martian" humans can live, and walk about and do stuff on the surface of Mars without spacesuits, is to blanket the entire PLANET in an envelop of gas DENSE enough to maintain roughly one standard atmosphere's pressure under Mars' puny gravity. Such an atmosphere would squeeze any diatomic oxygen molecules UP away from the surface, to boil away into space, or maybe form a layer of the atmosphere which MIGHT be breathable, if not for the fact that it's dozens of miles away from the surface, or hundreds of miles perhaps... (as the oxygen would be less dense, the same reason you don't find much hydrogen gas, either as single atoms or diatomic gas molecules, nor helium gas, for that matter, floating freely near the ground on Earth, as THOSE gases are less dense than the prevailing oxygen and nitrogen, etc. which they're more buoyant than, and hence, not readily found at or near the surface, (the hard ground, or the wet, watery parts) of the planet).
You'd need to find a substance capable of carrying O2 in the air, or oxygen by itself, bonded to something else, that human lungs would be capable of stripping out. Like water, for example, except our ancestors lost the ability to extract oxygen from water eons ago. Also, liquid water wouldn't stay liquid there long, either freezing, or boiling away into space due to low pressure. So again, yeah.
Our reign has gone on long enough. Indeed. Summon the meteors.
Yes, every nuclear system put into operation is perfectly safe... until it isn't. GE and Hitachi said that the Fukushima reactor design was safe, didn't they? (Even after at least one of their engineers resigned over safety concerns).
Debate is a form of harassment. Do not question my truth.
There are places on Earth, I suspect, or near it, where one can experience the same atmospheric pressure, lack of breathable oxygen, sub-sub-SUB-zero temperatures, as one would encounter on Mars' surface!
Just get into a REALLY BIG hot air balloon, and fly to the upper reaches of the atmosphere. DO NOT bring any protective equipment. As you get really high up, a tiny fraction of the way to that altitude, and become light-headed, pass out, and also freeze to death, (all the while accumulating chest-x-ray after chest-x-ray's worth of hard radiation from space, that would cause you massive cancerous tumors you won't live long enough to die from,) you can reflect on how much trying to live on Mars outside of a pressurized, protected, fully-self-contained, heated, etc.etc.etc. life-supporting enclosure, (much like a moon-base or space station would require,) would SUCK, and how only a moron would let romantic science fiction fantasies from decades, or centuries passed, when we didn't yet know how utterly inhospitable to humans, (or probably very nearly any multicellular life,) Mars actually is, convince him to try something so ruinous, wasteful, idiotic, and pointless.
That said, ENJOY Mars, folks!
Our reign has gone on long enough. Indeed. Summon the meteors.
No. A mass driver is a catapult based engine. I'm looking for an ion rocket based on fumes boiled out of rock, probably by a laser. Fast ejection velocity, not large amounts of ejection. I'd agree that a mass driver would probably be easier to build, but it's not at all what I was looking for.
FWIW, I'm dreaming of far ahead, with space habitats being long term living facilities that move slowly between the stars scavenging from free planets and asteroids, and moving at just enough faster than the local drift to continually encounter new areas to mine for resources. So my dream engine is quite conservative with respect to it's need for mass, but also doesn't require exotic substances that are hard to find outside of a deep gravity well. Hydrogen (relatively) is abundant in the form of methane, ammonia, etc. Silicon dioxide is reasonably available in the form of rocks. Fuse hydrogen for energy, use the energy to split Silicon Dioxide into Silicon and Oxygen. Save the Oxygen for breathing, etc. eject the Silicon as high velocity (as high as you can reasonably get) ions. A closed ecology can only go so far. There will always be leaks and the need for new resources. But you don't want to expend more than you need to.
We aren't near that point yet, but that's the direction I'd like our tools to be developing.
I think we've pushed this "anyone can grow up to be president" thing too far.
loony loony loony
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
And it's not done yet, it will rise in the sky tomorrow and attack you again. Day after day, it will seek you out, it's relentless.
Try Rocket Ship Galileo, 1947. That book was largely about the nuclear rocket, instead of using it as part of the plot. Heinlein did get the reaction mass wrong, planning to use the heaviest feasible atoms rather than the lightest.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
You've never "defeated" anyone. You're just like the proverbial pigeon playing chess, strutting around crapping on the board thinking you've won when none of your arguments have ever stood up to any scrutiny. There are places you can go to get help.
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
https://en.wikipedia.org/wiki/...
NERVA was considered by the AEC, SNPO and NASA to be a highly successful program; it met or exceeded its program goals. Its principal objective was to "establish a technology base for nuclear rocket engine systems to be utilized in the design and development of propulsion systems for space mission application".[1] Virtually all space mission plans that use nuclear thermal rockets use derivative designs from the NERVA NRX or Pewee.
Wow, didn't know that 4 people who profess to like your "software" constitutes "many orders of magnitude". I hope you don't program like you do math.
Also, some people like to eat human feces. Doesn't mean it's good.
Hope they bring your meds to your padded room on time today.
Cheers
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
*sigh* Nope. guess your meds were late again.
Well, there's always tomorrow.
How about you provide a link to each of those comments made by the people you claim made them.
BTW, writing a text file parser is not a hard task.
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
Nah, I just don't care. Keeping you busy here keeps you from posting your host spam elsewhere. Mission accomplished!
Until next time!
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"