New Mars Forums

For crying out loud, a GCNR is a science fiction engine, TRL of 1, you have NO BLOODY CLUE what it's power density would be of IF it could even be built, or what mass it would be and what launch vehicle it would need, you might as well be talking about the power density of anti-matter.  Solar technology is mature and scalable the engineering to make the array level power density higher is just engineering of deployment structures and trusses the theoretical limits are what the cells alone would produce, this is dirt simple engineering compared to any kind of nuclear system.  The ROSA array was developed with a NASA grant for a few MILLION dollars, the power density is 200-400 W/kg at the wing level according to the manufacturer.  Their difference in the nearness and cost to get more power and more power density from solar vs nuclear is just staggering, the nuclear stuff is Billions of dollars and decades vs millions and a few years for solar, how are people so grossly misinformed, who is spreading all this garbage?

I'm talking about actual hardware that's either exists now or is about to come out of the lab, if your going to talk science fiction nuclear systems then I'll come back with Fusion powered Magnetoplasmadynamic thrusters that could theoretically put a Megawatt of power through a device the size of a 5 gallon bucket and produce 200 N, and these things have actually been made and operated in labs.

SEP tug stages, solar + thrusters + propellent + tank are expected to be about the same or LESS mass then the payload and will move the payload from LEO to LMO with a stop at L2 if you wish, add a bit more propellent and you can move your payload BACK to LEO/L2.  They beat NTR in payload fraction even for the simplest TMI in which the payload has to make a direct (dangerous) entry to Mars atmosphere, but the SEP can give you soooo much more, a parking orbit without a heat-shield, return to Earth and then reusability of both the tug AND the payload.  Will the SEP tug need Heavy-lift?  If your monolithic payload already needs heavy-lift then it would be stupid not to use it for lifting the stage too, EVERY TMI stage ever proposed have been comparable in mass to the payload it pushes through TMI so it has commonality with the launch vehicle that puts the payload in LEO, the question is how MANY TMI stages you need, SEP has by far the best ratio at 1:1 with the potential for 1:2 if we can get into the 20-30k ISP ranges.

Your information is woefully out of date, Solar easily exceeds Nuclear power density in the Inner solar system (for in-space power, planetary surfaces are a very different environment), you need to be somewhere past Jupiter for Nuclear to be superior now.  NASA is developing 300+ W/kg Solar arrays and theoretical limits are in the 1000 W/kg range.  Nuclear systems simply can't reach that power density because they are thermal and need massive radiators and a whole working-fluid/turbine systems.  This is what people ignore about Nuclear, they look at the mass of a core and ignore the rest of the system which is 90% of the mass and it's this part of the system which faces fundamental Carnot efficiency limits that give us little hope of a breakthrough improvement.

Yes that's how long it would take with NO SUPPORT at all, the commercial and small funding deep-space probes Electric propulsion and solar panels would give us human-flight capable systems in that kind of time-frame.  IF we actually invested heavily in developing it then that could be considerably faster.  This is in contrast to nuclear systems which are moving at a rate of zero with zero funding.  NASA should put it's money on accelerating something that is not completely dependent upon NASA, just like NASA should buy commercial launch rockets rather then build boondoggles that it is the only customer for.

No the technology has never been competitive with Solar for power, or with Big Dumb Boosters for propulsion, the 'politics' stuff is a BS excuse that Nuclear proponents have used for decades to nurse their failure and bitterness.  I should hardly be surprised this sentiment is rampant on these forums considering Zubrin himself is absolutely dripping in this kind of resentment for politicians and half-concealed self-flattery "If only they had listened to ME we would be on Mars now!".

Double standard much, where are the 10 MW space based nuclear reactors ready to launch?   Our largest Arrays is the ROSA from Deployable Space System at 63 m^3, a dozen of these would be used to create a MegaROSA system of 750 m^3 and 300 kw, less then one order of magnitude short of the football field in area and enough power for things like Asteroid Redirect, so actually not that far off.  The ROSA arrays are set to become the new industry standard on commercial satellites too.

You 'accept' an error if you think nuclear systems are higher power density then solar.  And everyone in the SEP system field acknowledges that the power density of the energy source is the Primary determinant of the overall vehicles performance because the mass of thrusters hardware is minimal and scales very well, and the propellent fractions are already wonderfully low, so low that we would generally want to trade that back for higher thrust and shorter duration, which requires more power.  So yes it is all about the power source density.

Astronauts CAN WALK after returning from the ISS, as I said it is a myth that people are crippled by 6 months of zero-G, that kind of stuff only happened a decade ago when we did not have the present exercise schedules.  It is a solved problem, the Astronauts will need 3 days of safety recuperation on the surface because of adjustment of the shape of the eye that makes vision blurry, this is the ONLY current restriction that Astronauts have now upon returning to Earth, they can't drive vehicles for 3 days after returning to 1 G, we would thus not expect them to make any EVA's for comparable period on Mars.  They will be walking around in the Habitat just fine for thouse 3 days waiting to get out on the surface.

I don't know what the solution to radiation is either, active magnetic based shielding is just one of many ideas that may not work.  I just know that the solution is NOT passive Mass of ANY kind, their is hardly any difference between aluminum and liquid hydrogen (the best shielding) when it comes to stopping GCR, you would need a 200 tons of Aluminum and 100 tons of Hydrogen, both are equally unfeasible even if the later is half as much.

kbd512:  Your critique of SEP is completely baseless.  You seem to think that the technology can only work at small scale.  That is where it is currently being used because that is the size of our unmanned systems like satellites and probes, the performance of the SEP is currently being used to reduce the size of the launch rocket and add multiple destinations/lifespan to satellites because this is most cost effective first utilization.  But that has nothing to do with what scale it CAN operate at, it's like saying in 1945 that Rockets would never scale to bigger then a V2 because that's all that had been done so far.

The only limiting factor to SEP scaling is the Solar, and we have a 40 year history of higher and higher power availability on every type of space vehicle.  Electric propulsion systems and Solar arrays gain higher power-to-weight ratios as they scale up.  This scaling up is not a simple as just making a bigger tank of fuel and a bigger rocket engine, we have to do significant redesign and optimization of lots of hardware but the direction has always consistently been towards a higher performance system that has positive scaling factors.  It is just a matter of time and clustering of large numbers of solar arrays and electric thrusters into a single vehicle to create something that reach the size and pushing-capacity to move human spaceflight level masses.

I'm all for Technology development, and NASA badly needs to be allowed to redirect all that 'launch vehicle' boondoggle money into tech as the Obama administration tried to do.  But I disagree on all of the things you've point at as worthy of development, the current crop of tech that NASA is looking at such as Mars EDL, and mitigating propellent boil-off are the best choices, they just don't have the budget to do more then the top few choices, and slowly at that.  All of the technologies your asking for are on the other hand dead-ends or unnecessary and wouldn't in my opinion be deserving of any development funding.

Nuclear rockets have always been pie-in-the-sky, they are impossible to develop incrementally on the ground due to radiation release, the ISP they offer is no longer remotely attractive compared to what a SEP system can offer right now, their is zero reason to invest in this technology and that's exactly what is being invested in it a big zero.  I don't know why this forum is full of people who feel in love with Nuclear propulsion 20 years ago and never reconsidered that the mighty N might not be the ultimate solution to everything in space (I know the Hollywood movies certainly give this impression), but your ALL chasing a phantom that will never see the light of day.

Artificial gravity sounds nice, but we have enough ISS experience to send people up for 6 months and have them come down into Earth gravity and be good to go in a few days, they are not cripples as some people like to exaggerate.  In other words we can get to Mars in ISS derived habs and just recuperate for a tiny fraction of the surface stay time upon landing in lander/habitat, a trivial operational constraint that allows us to dispense with all the engineering of spinning stuff.

Radiation shielding against Solar Flares is basically a solved problem, we use a modest water tank 'storm shelter', every proposed Mars transit vehicle has included this for decades now and no one expects it to be a problem to built it or do it and it hardly adds any mass to the vehicle given crew water needs, this radiation presents NO barrier to NASA.  Cosmic Rays are the radiation that is currently the show stopper and which NASA has no solution for because their is NO passive shielding solution short hundreds of g/cm^3 which is far beyond our mass budgets.  Either we will find some kind of active shielding in space, discover that the dosages are less damaging then previously thought based on animal studies, focus on getting underground on Mars so the crew only gets the in-Space dosage, or just raise the chance of death threshold for astronauts.  Radiation deserves study but we should absolutely NOT be down-selecting to 'passive shielding' at this time.

The OP is on a better track when he mentions injecting heat, but this is not the same as Fracking.  Fracking just means fracturing with injected fluid and this is ulikely to be effective in producing water on Mars, either the water is frozen and it won't flow or it's not an you can just pump it without any new fractures.  Thermal injection usually with steam is used in Tar-Sands and Heavy oil, obviously injecting steam to get out water would be redundant, so hot compressed CO2 looks to be the best bet, in the oil industry this is called 'TEOR' 'Thermal Enhanced Oil Recovery'.  CO2 is already commonly used in place of steam so this looks to be available technology should it be necessary.  The need to characterize the sub-surface ice will be key to knowing if this is necessary or viable.

The main energy cost is in heating the injected fluid, as we would need to compress the CO2 as well that will heat it substantially.  I'd think you could use a solar tube type collector to pre-heat the atmosphere to modest temperatures then rapidly compress and immediately inject the gas, that would offer a high efficiency as the pre-heat is effectively concentrated by the later compression.

Didn't the F-1 also have some TERRIBLE jack-hammering issue that came close to destroying some of the Saturn V rockets???

Like GW said earlier, these rockets are absolutely obsolete, the fact that anyone is even THINKING about this and offering it up for use shows the complete failure of LM/Boeing rocket engineers to match the Russian Kero/Lox performance.

Oil is defiantly of biological origin, carbon isotopic ratios established this for Earth, abiotic oil has always been a junk science claim to attempt to pretend these resources are not scarce, the oil-on-mars stuff is just pure crank nonsense.  METHANE can be abiotic, but abiotic processes 'crack' hydrocarbons into shorter smaller molecules, they don't form them into longer ones, this is why coal/oil are 'cooked' into Natural ga by geologic heat and pressure, not the other way around.  Some of our Natural gas deposits may have small amounts of abiotic Methane in them at some tiny fraction, their are also huge deposits of not commercially valuable methane (far more then in all the commercial reserves) dissolved in underground water as well, and obviously all the methane in the Earths primitive atmosphere was initially abiotic and was 'biotic' only after thouse first microbes fixed the carbon.

If your goal is to terraform Mars then you need to release Methane into the atmosphere not consume it as would be done by the digestion machine I described.  Their is no biological process that we can do in a vat that is going to produce more Methane then the process that is feeding it could have just created directly.  Methane generating organisms on Earth are decomposers, if we synthesize 'food' that consists of long-chaim hydrocarbons being fed to these decomposers then we would have more methane by just making methane rather then long-chain food.  Only if we had long-chain hydrocarbons for some other reason, like a waste byproduct from agriculture would it makes sense to feed them too methanogenic bacteria, but ultimately I think it's more likely that agricultural wastes will be more valuable for recycling within the artificial biosphere mainly because of the trace minerals and nutrients they contain, things that will be much more difficult to replace then the bulk hydrocarbon content of the waste.  So were just likely to run the same sabeteir-electrolysis type methane synthesizers that we use to make propellent and dump the 'fuel' right to the atmosphere to produce a greenhouse effect.

We are seeing methane releases on Mars now, and that could be a biotic or abiotic process.  In either case accelerating or accentuating this release would be a potent greenhouse gas.  This might be simpler/more energy efficient then trying to run a factory to produce Methane, the 'stimulation' of the Methane from Mars itself might consist of drilling wells and injecting more of what ever material is the limiting factor in the current generation process be it biotic or abiotic their will always be a limiting factor.  Frackturing the rock to allow more venting of Methane already present or which is being stimulated, were already doing this by accident on gas fields.

P.S.  Shouldn't this have gone in terraforming sub-forum?

NASA hardly even mentions Nuclear propulsion even in passing anymore and only in the scope 'advanced propulsion' indicating they are not married to Nuclear, the trend is ALL towards SEP, a technology that NASA continues to invest in, use and improve upon.  .  Their is no long any mismatch between where the rhetoric and the development action is on the part of NASA.  That mismatch existed in the 90's but it's gone now, people need to get with the times and look at what NASA is doing now, not what they remember from decades past.

You keep saying that the 'sun pulls us' and 'centripetal acceleration' as if this is free energy, you don't change orbits in space without expelling something out the back of the vehicle and THAT is what changes your orbit.  The sun is not doing anything for you other then acting as the central body in a 3 body problem and their are no free lunches.

You seem to reject chemical rockets but if Orion is your vehicle from LVO up to SVL1 then THAT IS CHEMICAL, not only is the service module of Orion chemical, the lifespan of the Orion is so short I'm doubtful any reasonable mass SEP vehicle could make the journey in a reasonable time frame.

This two spaceship architecture your describing has each vehicle capable of making the whole journey with the propellent that it left Earth with.  The only thing your saving is that the crew goes 'fast' from LVO up to SVL1, but there's no point to that, Venus doesn't have a Radiation belt like Earth that compels up to go fast in that phase of the journey, a slow spiral out from Venus is fine.  The downsides are huge in that I'm using 2 whole vehicles to do the mission AND they have to haul along a capsule when inbound and outbound, so each vehicle now has to leave Earth with more propellent then if the Orion capsule was eliminated entirely.

Ion Engines are great because they allow us to avoid breaking up the vehicle and making elaborate rendezvouses like this.  Each time we transfer crew and do a rendezvous we have to add mass in redundant habitat, and habitats are non-linear with respect to mass and endurance.  If I need to keep the crew alive for half the journey in one habitat and the other half in another habitat then the sum of the two habitats is MUCH MORE then if I used one habitat for the whole journey.  In your scenario the consumables like food/water can only be restocked at Earth so the crew has to leave supplies behind on their inbound vehicle in order that some future crew can use thouse supplies when said vehicle is their return vehicle.

Just use one Ion engine interplanetary vehicle to go from Earth-Moon L1 all the way to Low Venus orbit and back to EML1.  No second vehicle, no second habitat, no rendezvous, no docking, much lower total mass and total propellent.  For that matter I would leave the silly Orion capsule back at EML1, if I'm reusing an Ion engine vehicle and parking it back at EML1 every time I use it then my ride back into the Earth gravity well should be waiting for me their at EML1, not hauled around with me in deep-space, you only need your reentry vehicle with you if your coming in fast and can't stop.  I'm going reusable then that two rendezvous to make a clean separation between my 'in-space-only park-able at Lagrange points' and my 'atmospheric launch/entry, must relaunch to reuse' stuff makes sense, when the 'terrain' is changing and you faced with destruction of your vehicle if you take it across the bad terrain then having a rendezvous and vehicle change makes sense.

But out in deep space around Venus theirs no compelling reason to put in a rendezvous at the location your describing.  That trip from LVO up to SVL1 done with Ion drives is probably only 10-15% propellent mass fraction and 2-3 months, really not much compared to the whole journey or even just the rest of the return trip which is 6-8 months.

I think this thread got off to a very bad start by mention a 'return' of Shuttle, that's just insane and is sucking up all the LOX.

If you kept the discussion to just how to make use of the External tank in orbit as might have been done then we would be doing some armchair engineering on some dead hardware but it would still be a decent discussion so long as we all acknowledge that it's not going to happen but rather represents some could-have-been.  Roberts idea in the opening post is probably the best that could be done with the tank, some combination of pre-installed hatches, and on orbit rework with new air-locks installed onto the hatches.

Problem is that we don't get 'habitats' from this we get 'giant zero-g playrooms', without all the mass of equipment that forms a habitat their is no functionality to the large pressure vessel that a tank is.  Just because current space-stations provide low volume per person and are a bit cramped dose not mean we can get a good habitat by providing only volume, just as we can't replace a cramped NY condo with an unfurnished aircraft hangar.  Without many many more tons of equipment the huge volume of the tank dose not increase the population of ISS.

This is a major issue with tank-habitat conversion and I also have it with Bigelow concepts, the mockups so far released make poor use of the volume because they are designing the things to maximize volume and they look to be under equipped with all the other things necessary to make a living space (life-support, water, sanitation, galley etc etc).  Now IF Bigelow had a plan for actually installing a furnishing this equipment then all would be great, but everything we have seen so far is 'monolithic' with all the furnishings inside the core of module, and that core is much smaller in volume and mass then what could be put into a rigid Destiny module type thing.

What inflatable and 'wet' habitat concepts need is outfitting by something like the Leonardo Pressurized Logistics Module.  It can be packed solid with equipment racks and then connected by CBM to allow that equipment to be moved into the station space and installed.  When furnishing a really large space we would need to include deck-floor panels.  Then the pressure vessel just needs to have an few 'frame' rails and conduits for cabling for all these furnishings to attach too, which would be easy enough in an inflatable and even easier in a propellent tank.  This may require several flights of equipment for every flight of a pressure vessel as we would expect and hope, the big pressure vessel is more mass efficient per unit volume, so as a percentage of total it drops, but their is no point unless your going BIG, like high double digit populations.

What you want to end up with is something MORE cramped then ISS Destiny module which has an excessively large 2m x2m hall through the middle, rather you would want to have hallways only 2m x 1m, the minimum size a person can comfortably go through and what much of the Russian Functional Cargo Block looks like inside.  If we have a huge volume to fill then we just a whole bunch of lateral decks and pierce it through with multiple hallways.  The same way a hotel or cruise ship is built on Earth.  Allocate a few 'rooms' for gathering and then allocate ALL the rest for equipment and bunk space.  Now you're going to have the ability to house people at enough of a density that your big volume is actually getting you more population which was the point of all this.

I think the 0.1 g acceleration rate requirement is WAY too high, that's the kind of acceleration that gets you to planets in days when we should be targeting months.  Electrical propulsion systems are not going to get anywhere near that kind of thrust level under any currently conceivable device.  Much lower accelerations are perfectly viable and bring the power requirements into the realm of possible.

I think the break through that a Nuclear power system in space needs is that of a less massive heat radiator as that's the most massive part of the system.

Current radiator tech is based on fluid in tubes that run through panels, very bulky and inefficient in surface area.  Maximizing the heat dissipation into a vacuum is done by increasing surface area, so having the fluid in tiny droplets in free-space will be the optimum configuration.  Now obviously we must not be losing the coolant fluid so these droplets need to be a 'spray' which is being continually emitted and collected again with virtually nothing being lost.  If the coolant was also the propellent then perhaps a little loss would be acceptable, but our propellents are probably gaseous and would not be usable as a coolant, some kind of ionic salt seems to be a more likely coolant.

Two possible configurations present themselves, a 'fountain' configuration that uses the vehicles acceleration to control the droplets, and 'cotton-candy-machine' which would be centripetal and independent of vehicle acceleration.  Which would be better I'm not sure, but either one looks to have the potential to provide a huge reduction in thermal radiator mass.

Lastly some additional performance might be gained in a nuclear ion engine system if the thermal energy of the reactor could do the job of ionizing the propellent, ionization is a significant portion of the energy consumption and if it would be done with the low grade thermal energy then it would avoid the conversion losses of converting to electrical and then using the electricity to do the ionization.  Unfortunately this would certainly entail a massive redesign of the ion engine, for one it is likely that the engine has to be immediately adjacent to the core so that the ionized gass can be expelled before it reverts back to neutral gas.

Skylab was not wet launched, wet means full of rocket fuel at the time of launch.

Ok back on top now, pictures of the Drone ship have been released (probably not by SpaceX itself but by 'space paparazzi').  Their is some burn damage and some charred/melted 20ft shipping containers, and some pancaked scrap metal on the deck.  Hard landing seems a bit of an understatement, it was more of a crash, not an explosion just a crash.

This is an interesting speculative animation of what might have a happened. 

I think this looks close, but some of the bottom/top of the rocket was in fact shorn off as it went over the side and this is what the scrap on the deck is as it is clearly not a whole rocket in that pile.

I'm not aware of any such treaty stipulation, Russians have been leaving empty booster rockets in LEO for AGES with nary a whiff of life-cycle planning, that's the space-junk problem.  Shuttle Tanks weren't left in orbit because.  1)  It would reduce other payload that was actually needed/desired.  2)  The thing is so incredibly light and low density it would have a rapidly decaying orbit meaning we can not effectively stockpile them  3)  They would be completely unguided, uncontrollable tumbling and likely dangerous to approach again if just left them free floating  4)  They have nasty residual propellents in them which are going to boil  5)  ALL the crazy ideas about sticking external tanks together and living in them and such were completely bonkers, we have NO ability to cut into, modify, seal up any of this stuff in-space.  The only propositions that had any chance of working were with a modified tank with a port in the bottom and that was never made cause we built a REAL space-station instead, just because the ISS is also made of aluminum cans dose not mean any aluminum can makes a good space-station.