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How come everybody beats up on nuclear power? The modern RTG is a marvel of durability and safety, and the "threat" they pose is entirely overstated.
"A few pounds of plutonium might not seem dangerous on a planetary scale, but keep in mind that it's one of the most toxic substances out there. If you inhale even a few atoms of it, your chances of getting cancer are very near 100%. Anyhow, RTGs don't develop a whole lot of power, usually a few hundred watts if that..."
First-first of all, atoms are small. Real small. You would need a million billion billion atoms of Plutonium to even be visible with the best optical microscope. You have already inhaled a few atoms from nuclear testing and Chernobyl.
Plutonium is fairly nasty, but it is not intensely radioactive unless it is being used in a nuclear reactor, which an RTG is NOT. Secondly, the Plutonium is stored as a sinterd metal oxide which is extremely hard, and will only fracture into a few large pieces if broken, not into a fine powder. Thirdly, the US-made RTGs are extraordinarily resistant to damage, and have survived with little or no leakage at all through a battery of torture tests, like terminal velocity impacts, several thousand degree arcjet furnace, sea water immersion, and even firing fairly large bullets at them to simulate a launch disaster. All modern designed RTGs that have accidently re-enterd Earth's atmosphere didn't leak at all. Bet you didn't know some already came back down from failed satelites and Apollo 13's Lunar Module. US RTGs are virtually impenitrable.
The danger of the material itself is greatly overestimated too, the radiation from Pu-238 that you have to worry about is predominantly alpha radiation, which is easily blocked by a thick sheet of paper, much less a RTG hardend casing. Furthermore, the data used to extrapolate the huge jump in lung cancer with inhilation of small quantities by those heralding plutonium as the doomsday poison is shakey if not fraudulent, and consider its source... US and Russian nuclear testing has thrown more Plutonium areosol (and worse things!) directly into the air worldwide than Nasa could dream about putting into RTGs, and yet, we're all still here aren't we?
I would actually think that the small amounts of radiation put off by a running RTG would be a -good- thing, since it would help sterilize the spacecraft after it lands, which would make the chance of us accidently discovering "life on Mars that looks alot like life on Earth near Cape Canaveral" lower.
Solar power, if you haven't noticed, doesn't make a whole lot of power either per weight, and it has one fatal drawback on Mars... the dust adheres to them. The Pathfinder base station probe would still be sending us pictures of Martian sunrises and weather forecasts if its solar panels didn't lose THREE PERCENT of output a day. While this has improved a little, it hasn't improved much... An RTG need not supply all the power for motors to move around either, if it recharged a battery that was used for motion now and then instead (which is what Nasa rovers do anyway, stop and go) and have a life span of YEARS instead of a few weeks of exploring!
A nuclear thermal engine can't sit on the end of a really long truss on the side, or easily on the back, since the reactor itself IS the rocket chaimber. It has to sit in the back, and pretty close to the crew section, so it would definatly use submarine-style doped polymer radiation shield. Somthing like this: http://spaceflight.nasa.gov/gallery....186.jpg
As far as areobreaking, with the kind of power that the NTR engines have, it might not be nessesarry at all. If not, or you want to maximize payload, perhaps an inflatable shield filled with foam instead of gas, like the crack-filler stuff that comes in cans from the hardware store, which would offer excelent insulation.. if it could handle the heat. It would be deployed in LEO before setting off for Mars. If they were light enough, you could even carry two, one for Mars and one for Earth given the differing atmosphere thickness.
Hmmmm so if you packed a 50kg Stirling-Cycle RTG and, say, another 50kg of batteries/generators/shielding though... would 100kg be a small price to pay for a Mars rover with unlimited range and surface duration? Sounds like a bargain to me.
Nuclear thermal is the obvious choice for a manned Mars mission. Although it will be fairly expensive to develop, the benefits are plainly evident. The USAF considerd using a NTR engine to replace the hypergolic first stage of their rockets, which would have had an efficency of 225% of that for the Shuttle's SSME cryogenic engine, the most efficient rocket in the world.
Instead of a cramped tuna can for four to ride out over 6-12 months of each leg, more of a bulky capsule in the case of Mars Direct's ERV, one ship launched in two pieces by an SDV, perhaps fueled and given a fueled Mars decent lander by EELV HLVs, that is roomie and safe with a heavy-duty cosmic radiation shield that can get there in four months to avoid crew deconditioning.
Plus, this nuclear engine would be reuseable, since it would carry all or most of the fuel it would need to return to Earth from Mars orbit, eliminating the need for a ERV at all.
Yes definatly. I didn't realize that the Mars Direct ERV was that small... it would definatly have to be pretty roomie, especially with the supplies it will need. There is also the psychological strain put on the crew, which would not have been on Earth for almost a year and probobly a little decondtioned still from the trip up from Earth.
I like this plan, though there are a couple of things that could be added to make it better... if the orbital transfer habitat were propelled by nuclear rockets fueled with LH2, which have about double the efficency of LOX/LH and tripple the efficency of LOX/Liquid CH4, then you don't need to refuel the hab module in Mars orbit at all. The reactor could power a condenser system that would prevent fuel boil-off for a lengthy stay on the surface.
So, since you don't need to haul up tons of fuel to the transfer hab, you could also make the Decent/Acent vehicle much smaller, since it would only have to carry the crew and a few hundred kilos of rocks and hard drives. In fact, if you could keep the down-mass of the decent vehicle low enough, you could skip the need for a huge Martian fuel factory and its LH2 feedstock entirely if storable acent fuel were sent with the cargo flight.
Since I love to "think big," I am imagining the transfer hab stage being launched by a pair of 120 tonne SDVs, one with a large version of TransHab with room for six and all the food, water, and life support gear needed for the whole journey, the water or polymer radiation sheild, the solar flare "storm vault," and perhaps the storable-propellant Mars Decent Vehicle. The other launch would be the nuclear propulsion stage with solid core thermal engines with bimodal power generation, and the "command module" with all the flight electronics/communications/Mars satelites etc. These would be mated up in LEO, and if nessesarry fueled with EELV HLVs, then tested by an OSP crew and finally manned by two more.
The cargo flight would be the huge "megalander," which could hopefully itself be pressurized for use as a "garage" or lab space, along with a small power reactor, acent vehicle fuel, science payload, and of course another fairly large Mars-only TransHab. This would be deliverd to Mars orbit by a second nuclear transfer stage, which would also be reuseable.
The elevator idea would be nice for hauling bulk cargo up like rocket fuel and satellites, but I have some reservations about how reliable it will be with all the space junk floating around or any small imperfections in the CNT composit cable that might lead to somthing... catastrophic.
It will be entirely useless for human travel without a much larger version, since anybody sent up the elevator would get too big a dose of radiation without carrying a massive shield. Apollo was okay because it only spent an hour or two in the radiation belt around Earth, spending 24-48 even 72 times as long in the region gives you 24-48 even 72 times the dose.
I also have my doubts that it would be useful in the near term over an Energia/SDV HLLV paired with semi-reuseable EELVs with flyback boosters, simply because it would not be easy to haul up large objects. The ISS debacle compared with Skylab should have taught us all the lesson quite clearly that building large things in orbit in little pieces is insane.
Finally, about asteroid mining... asteroid mining is a completly crazy idea. I don't think it will ever be able to compete with Earth-based mining operations, simply because its too hard to get the stuff back to Earth in bulk. Only five tons a day from an elevator and a few dozen billion dollars for the mining operation, and the millions/billions a year used to push the stuff back to Earth? Not unless Greenpeace gets the UN to ban mineral mining or somthing.
The only hope for mining minerals from asteroids is to bring the asteroid to a large "heavy" space elevator station in GEO, and send down alot more than five tons a day... even then, it will be very hard to justify the massive cost of pushing an asteroid into Earth orbit! ...No. If we want humanity to exploit the wealth of the solar system, we have to bring humanity to it, not it to Earth. After all, people don't weigh that much...
Ehhh there is a difference between the Moon and Mars that does warrent MSR before a human mission is sent, besides the fact that we don't have Communist Russia to beat...:
The Martian dust does indeed contain some pretty harsh chemical salts and peroxides that could be harmful to humans, which would be difficult to avoid exposure to. With Nasa in its "safe spaceflight or no spaceflight" frenzy, I doubt they are willing to take the chance. Since you can't send up lab rats or a large biology package, the best thing to do is bring some of the dust to Earth. I bet the dust on Mars is pretty well homogeneous from a few billion years of being mixed by the winds, so any sample will do.
It would also be nice if Nasa could find some place with underground water or surface ice or somthing, and turn it into O2/LH, so human crews won't have to skimp on water consumption (hot shower? yay! *grin*) and won't have to bring any Hydrogen feedstock from Earth at all, saving an EELV HLV launch or two worth of mass that you could pack a few Martian GPS/Telecom satellites on the TMI cargo stage or somthing else nice. If TransHab could be built light enough, then you could pack one instead of the LH fuel and have lots more pressurized space. (yay!)
Oh yeah and about nuclear rocket -exaust-...
Hydrogen can't really become radioactive to any great degree with its extremely simple and stable nucleous, so this isn't a big problem, though it would be hard to build a solid core NTR engine that retains 100% of its fuel mass. Some small leakage would probobly occur, but were the engine fired in the upper atmosphere, the material would be so dispursed that the dose recieved on the ground would be nil. Now as Gas Core thermal engine would probobly have signifigant leakage... but a small price to pay for 6X-8X the ISP of SSMEs. Six times the payload, or Earth to Mars in 30 days?
Yeah, the relativly small mass of all the gear sent in Mars Direct and the pretty small size with long durations in cramped quarters never apealed to me, and I think borderlines on "fantastic," especially considering how hard it would be to include good radiation shielding and signifigant science equipment & lab space. Though the 1980's $400Bn battleship was outlandish, the optimum mission should be somewhere inbetween there and Mars Direct.
Besides the cost of vehicle construction and development, alot of the costs come from the sheer mass needed to get there per mass of payload. I like the idea of a Mars-based fuel factory to gas up an acent vehicle and rovers which would save a good amount of mass, but I wonder if instead of hauling an acent vehicle, could the fuel instead be used to gas up the manned decent vehicle instead to return to orbit?
Next up... with a nuclear powerd engine complete with a boil-off reclimation system, build a ship to get a human mission to Mars and back again with areobraking to Mars and Earth orbit fast, preferably with enough power for a direct abort with the use of reserve fuel. Mass should not be skimped on the manned transfer stage which should have a water/polymer cosmic radiation shield and make each leg in eight months either way with extra fuel. Six months on ISS is already pushing it, and I hate to say it, but if spinning your spacecraft doesn't make the engineer in you cringe, it should. It would definatly be based on a big TransHab, and hopefully have room and a large enough lander for SIX, not four.
The cargo mission could instead be powerd by a giant Hall thruster run by nuclear reactors if there would be a substantial mass advantage compared to a duplicate NTR stage, and if it is practical make the stage reuseable. If not, and the mass to the surface of Mars were increased dramaticly, then I think it is an acceptable loss. The cargo lander could areobrake and enter Mars atmosphere with the same shield, and have a one-shot expendable engine to soft land with. The mass of this payload module should be substantial, with the hab suporting double the volume of Mars Direct at least, keep the pressurized rover and drilling rig, and carry the propellant factory.
Hmmm that isn't a great deal of power for a large rover, but it might be if it were used in a sneaky way: Use the RTG to charge up a light-weight-as-possible battery and use that to drive the motors or high power science equipment for short periods in the day and recharge at night.
A vote on canceling OSP? Argh I can't stand the not knowing!
OSP wasn't going to carry any signifigant cargo from the outset I don't think, asside from a few kilos of speciality stuff or maybe an unmanned launching Progress style on a EELV HLV in the first place I hope... And its very encouraging that O'Keffe plans to do away with Shuttle, as least in its crewed form.
Buuut I still think a capsule is not the best choice. They still have less cross-range miles than I have teeth and will require a more involved and numerous costly recovery sites. Not to mention that they are harder on the crew during decent, cannot re-use their OMS engines, nor are much lighter than a lifting body. A X-38/HL-20 style lifting body with seats for six or four and 500kg of cargo might be just light enough to ensure single-CCB Delta-IV compatibility.
Hmmm rebuilding the Energia booster using American facilities would be kinda pricey I imagine... but as long as it would cost less than a billion dollars a launch, it still might be more economical than developing an SDV or the folley of building a Mars ship with suped-up EELVs. Does anybody have any idea how much it would cost to build a 120 ton SDV?
I also can't help but be a tad concerned about Mars Direct's pretty tight mass and volume constraints... it would be nice(er?) to launch a larger Earth-Orbit-to-Mars-Orbit and back nuclear engined ship launched by 1-2 SDVs/Energias and stocked with a (fueled?) decent/acent vehicle, liquid hydrogen fuel for the NTR engines, and a crew of 6-8 (via OSPs) brought up by a few EELV HLVs. The Mars unmanned payload, replete with a larger multi-TransHab base, possibly a pressurized garage for the rover, and alot more equipment than you could cram into a direct flight for a much more extensive survey if a one-way megalander could be devised. The same NTR transfer stage could also be reuseable and launch a large number of small GPS/Telecom/Recon satelites when it reaches orbit with a minimum of hassle.
The uranium fuel in the nuclear engines would last for several flights probobly, give mass margin for a radiation shield or more Mars base equipment, and would be able to keep the whole trip short to minimize risk and maximize flight rate, not to mention give direct abort ability. An initial investment for the NTR stage and a few extra initial HLLV launches initially I would think would be worthwhile even if they did cost alot more than $120M a pop if future HLLVs would not be needed later per-trip.
It seems that such a plan to go to the Moon first to mine ice would have a few other advantages besides saving fuel weight of the Mars ship on launch, and the proposed plan has a couple of drawbacks...:
Advantages:
-Learning to fly a verticle-down reuseable lander with signifigant mass, a requisit for a Mars mission. The high flight rates of the LBV will be excelent practice.
-Ready supply of water/fuel in Lunar orbit, saving launch mass for a Mars ship from Earth, which should be large as practical.
-Regaining a little public interest in Nasa, a nessesity to keep its coffers from being robbed by a "soup kitchens not rockets" future administration.
But, there are some disadvantages...
-The 8,000kg payloads to the Moon's surface frankly seem a little small to me. A large nuclear power plant needed to generate more fuel than Lunar operations would use may weigh as much as 20 tons (the max practical on EELVs) or a large solar farm would also be quite heavy. Spend the extra money on more EELV launches today to seperatly launch & fuel a much bigger 20 ton payload LBV in LEO today instead of a whole new vehicle down the road. ISS will require 40,000-70,000kg a year not counting construction to keep it up there. A mere 16,000kg to the Moon two or three times a year for supplies and construction sounds miniscule to me.
-Long transit times to Lunar orbit via the solar ion tug: as efficent as ion drive is, it is still very slow, too slow to fly anything manned, living, or containing cryogenics. Plus, building an ion drive that powerful would not be so simple a task as it might first sound. Instead, stick with a cryogenicly fueled orbital transfer tug that could haul enough fuel from the Moon for the round trip and be able to make it in a few days. This way, a slightly modified OSP itself could be used as a "manned payload module" if transit times were kept short. If carrying that amount of fuel from the Moon's surface would be a problem, then its time that Nasa dusted off an old new technology...
Nuclear thermal rocket engines. It is not difficult to imagine an engine capable of a 225% improvement in fuel efficency over the best LOX/LH engines and still have enough thrust for a fast flight, engines of 180-190% efficency were tested in the 1960s. A well built nuclear rocket would actually be safer than a regular combustion rocket, since only one turbopump is needed. This same engine could simply be stacked up for use at a Gateway-launched manned Mars mission with few modifications. Double Martian payload for better radiation shielding, on-site hydrogen stocks, more drones, bigger labs, larger crews etc... or halve transit time if you prefer.
Cargo lander vehicles with such low masses and tugs with low useful flight rates will severely dampen meaningful not-flags-and-footprints missions off this damp rock. With economies of scale of increased flight rate and the development of a RS-84 flyback booster instead of SRBs/CBCs boosters, the 20,000kg version of the EELVs would permit cost effective routine flights carrying substantial masses to LEO such that Nasa could postpone "Shuttle-II" for a very long time.
Large 20 ton masses to the Lunar surface are really needed to start a Moon-to-Mars fueling strategy for routine high-mass flights when an SDV and go-ahead for a Mars mission are available down the road so we can expand humanity instead of just poke holes in Martian soil and find dead bugs only to go home for another few decades...
Now about the ISS...
The ISS cannot be "upgraded" quite so easily as Nasa would like I don't think. ISS is only somewhat modular, now the modules are all but welded together. Replacing the older sections of the station would be quite a feat, and even harder is to find replacement parts for such a complex beast that has had such a huge lead time in construction. Some small ISS contractors have already gone out of business, forcing Nasa to have Shuttle bring down bad parts to be fixed and relaunched. I think a day over 20 years for ISS is optimistic, putting the end-of-mission life around 2020 or so. If semireuseable EELV flights become common, this should not be too difficult to achieve with a ATV-style light orbital tug and OSP.
A capsule design may be less expensive and faster to develop, but I am not so sure that it would be any easier or less expensive to -operate-. And perhaps I have erred in not making it clear that a winged craft can include a lifting body akin to X-24/38 or HL-20...
Anyway, back on topic as far as capsule designs of similar volume to HL-20 or Zarya will still be pretty heavy if it is to use almost-off-the-shelf hardware. The only capsule of similar volume and capability studied by America that I know of is the "Big Gemini" cooked up in the Apollo days. It had all the cargo volume and equipment that OSP would need and then some, but would have weighed around 16,000kg, similar to Zarya. It might be possible to reduce its mass down to the limit for the Delta-IV (which Nasa seems bent on at least having capability for) but to do it in only four-five years is questionable.
Plus, given the ISS orbital inclination, there will need to be many more emergency landing sites for OSP if Nasa wants fast emergency return capability, and if speed is a major factor (such as an injured crewman), then you have to also consider the time-to-recovery element. An HL-20 style OSP will also be able to re-use its OMS engines and its heat shield, whereas the former is impossible for a capsule and difficult for the latter, given its much higher temperatures.
It is even possible that HL-20 could use a mostly metal foam heat shield, which even if it wern't truely reuseable, would be very durable and very easy to replace. Bolts, not glue. Not to mention that a lifting body also experiences fewer G's on re-entry.
A HL-20 fifting body, reduced in size for six crew and lightend to ride on Delta-IV Medium+ 5,4, is the ideal outcome for the OSP project.
Hmmm sounds interesting, and I do like the idea of having a Lunar-orbit staging area at a Lagrange with a ready supply of LH2. A couple of concerns though...
The solar ion tug, or for that matter anything ion-drive powerd, will be much too slow to fly a human or time sensitive payload (e.g. living material, speciality radioisotopes) up to Lunar orbit. Plus, we don't have alot of experience building a giant ion drive able to push 8-20 tons very fast.
Instead in the near-term, we start with a pair (one for backup manned return) of conventional cryogenic fuel tugs powerd by a SSME or RL10 type engine, since the tug won't ever have to store its fuel for very long with the short Earth/Moon trip times.
Since it isn't easy to land a large mass on the Moon, payloads should be limited to 20 tons, so only EELV class launchers will be really required. Two conventional LOX/LH tug would be launched fueled into LEO followed by the fueled lander and the propellant plant in four launches, flown to Lunar orbit, and the lander would bring down the fuel plant and refuel itself. Back up to Lunar orbit to refuel a tug, which goes back to Earth to pick up another waiting 20 tons cargo and either return with remaining fuel or be fueled by another EELV launch and back to the Moon to mate up with the LBV... etc.
In the not-so-midrange future, as hopefully a "Nerva-II" would be built (or even a GCNR, woohoo!) then might push multiple 20-ton or SDV scale payloads to the Moon, then there would be no more excuses to start setting up shop perminantly on Mars.
Hmmm back to the Moon ey?
I suppose that it wouldn't be a totally bad idea... test an ice-eating water/fuel/oxygen refinery, TransHab modules, life support gear etc. within easy(er) range of home. If Nasa intends to do anything there besides play golf or pick up more rocks though, they will have to build a base of some sort wouldn't they? And in that case, Nasa will need to build a medium lander module (20 ton minimum payload), which might be reuseable if fueled on the surface from ice, which could act as a Earth/Moon tug for flying over medium-sized stuff launched on heavy lift EELVs. OSP could mate up to it, fly to Lunar orbit, down, and back up just being another payload.
As such, OSP need not be a capsule at all, since the wings won't be a liability in a vacuum, and the reuseable lunar tug would have to break into Earth orbit for the next cargo anyway. This would save a greaaat deal from having to build TWO different OSP's.
I am hesitant to suggest using a Shuttle-Derived megabooster for Lunar cargos, because not only would you suffer a huge mass penalty to launch a cargo directly to Lunar orbit that is just fuel needed to get you there, but you have to be able to accuratly LAND the stuff when you get there, which would be tough to build a lander able to haul 40-60+ tons.
I would really, REALLY hope that too, since I hope Nasa has sinced learned the folley of pairing crew and heavy cargo, as people don't weigh much and require a very high quality rocket, and cargo doesn't. But...
http://www.slinews.com/slifinal.pdf
...it looks a bit like Nasa thinks there should be a "reuseable" Shuttle-II flying before ISS expires, with vehicle development decisions starting in 2005... Phrases like "reuseable," "Space Station crew and cargo," and "satelite repair" are making me ill, but it doesn't look like a done deal. HOPEFULLY Nasa will come to its senses and abandon anything like Shuttle. Look at the artists drawings... http://www.slinews.com
What I would like to see is the creation of a fly-back liquid booster powerd by the RS-84 designed specificly to fit 2-3 on a Delta-IV or Atlas-V core able to lift 20-30 (perhaps 40) tons to LEO. Even if the flyback boosters were attached to a payload faring I still don't see an easy way to re-use the Centaur upper stage. Somthing like this could cut launch costs in half right per-ton there if the boosters could be reused easily.
Sorry for hijacking the thread, back to OSP/cargo tug concerns...
The X-38 has one fatal flaw that takes it out of the running for OSP, in that it only has the hardware to come back -down-, none for rendevous, docking, or enough life support. It is also has no landing gear, which would be awfully nice to make landing gentler and recovery easier. It also was totally automated, no manual controls whatsoever except for the parafoil. Along with no provision for any propulsion outside of a throw-away solid rocket deorbit engine, which won't be good enough for orbital maneuvering.
Hence, if OSP is to have wings, it ought to be a 75% scale of HL-20. http://www.astronautix.com/craft/hl20.htm HL-20 has room for ten, and had a launch mass (escape rockets, OMS fuel, booster adapters, etc included) of around 16,000kg. This would give you room for six and maybe a little time-sentitive (eg living tissues) or specialty replacement cargo. This would put you near the limit of the Delta-IV Medium 5,4 launcher's payload to the ISS but if there were any weight-creep then it would require the Delta-IV Heavy or an Atlas-V with four or five SRBs.
HL-20 would also be able to re-use its OMS engines, be able to land on a runway, and have a more benign (1.5G) re-entry that would subject the heat shield to lower temperatures making shield reuseability easier. A capsule of similar internal volume (Big Gemini, Zarya "Super Soyuz") would weigh a similar amount with all launch hardware, require more potential landing sites (low cross-range flight), and subject the crew to 3-5G decents.
That would probobly be the ideal situation, and the course that Nasa ought to take I think, but the dollar signs are mounting at a frightening pace to build OSP and there is no talk of a orbital supply tug at all as far as I know.
I think one of the mounting questions if OSP should go forward is when or if Nasa intends to bring Shuttle-II online. I think the idea of a crewed reuseable medium launcher is a terrible idea to get us out of orbit. But if Nasa is bent on it, then it does become a question if its worth it to spend big money on OSP/cargo-tug when we have Shuttle 1.X already and the OSP/cargo-tug function would obviously be superceded with the advent of Shuttle-II. With room for three people each, its possible to modify Soyuz for longer on orbit life and send up two of them to fill the CRV role.
If OSP and a tug would wind up costing, say, $15-20Bn to develop and another $1.0-1.5Bn a year to operate when we are just going to turn around and throw them away after we're done with ISS, it may actually be less expensive to fly Shuttle two or three times a year.
This, combined with the huge army of people that would be layed off when Shuttle is retired, even if the Stack is modified into an SDV, then Congress may simply skip OSP/cargo-tug and wait for Shuttle-II that Nasa is going to build anyway.
As far as my take on OSP, having it able to take over entirely from Soyuz would be a nice ability to have, and adding room for six seats as opposed to four I don't think would be that hard. Even if all four seats aren't occupied, I am sure there are light-weight supplies and science gear that could fit in the extra space. In any event, even if OSP becomes a very small capsule like Apollo, the CTV version will probobly be too heavy to ride on the badly under-powerd Delta-IV single-core launcher without SRBs, and it is looking shakey if it could ride on the Delta-IV with the maximum number either. The no-SRB Delta-IV can haul around 7000kg I figure to an ISS orbit, and Apollo weighed around 6000kg for the capsule alone. No service module, escape rockets, or adapter.
Or... worst case senario... ISS is scaled back to a three-crew limit and forced to operate soley off of Soyuz/Progress/ATV flights with a greater focus on tending automated experiments rather than a large crew doing them by hand.
I don't mean to sound too incredulous, but thirty years sounds awfully optimistic. Other major componets, like the notoriously fragile US gyros and Russian batteries are also vital componets. I am not saying that ISS could not be sustained with sufficency maintenance until 2030 or so, but it will become an increasingly expensive and complicated endeavour that will require alot of mass to be brought up from the ground. More mass than can be reasonably launched without either Shuttle or an additional medium (~15 ton) cargo tug craft of some sort.
Hence, instead of spending the cash on developing OSP that has no destination outside ISS ATM and buying cargo tugs that might not have fuel for LEO/GTO work, plus the cost of maintaining a geriatric ISS, Congress might be suggesting to Nasa that they cut their losses by flying Shuttle until ISS gets too expensive to maintain, if the ISS can be repaired and flown for another decade or not. How much is an extra few years of zero-G science lab that hardly any voters care about worth?
Errr scaled down TO 75%...
Spacedaily had a thread concerning this that kind of branched off of the question if Nasa ought to design another space plane. A major issue for OSP that takes Apollo off the top of the list is that it has a very small internal volume, 6m^2, a third less than Soyuz even I think. Big Gemini/HL-20/Zarya have about 16m^2 each and seating for ten.
Hmmmm but doesn't Nasa need the OSP if they are going to retire Shuttle when the ISS is complete? ...A thought, that if Nasa does retire Shuttle when the last few modules of ISS are launched, won't there need to be a new (EELV-launched ATV-derived) cargo tug to make up the difference?
Plus, since ISS may run low of money and will begin to show its age pretty soon (like 2016 soon by some accounts, perhaps sooner) then like Mir ISS will probobly require alot of expensive, heavy maintenance equipment/parts/etc to maintain a safe station beyond that nice round figure date. Sooo...
The solution to the problem is pretty simple. Scale back ISS to the three-man-crew maximum, keep Soyuz for the CRV, and... *gulp*...Stick with a limited manned Shuttle flight schedule for the remainder. With the ESA ATV or derivitive and Progress helping out, the Shuttle launch rate might be kept low enough to simply reduce the risk of another catastrophy to acceptable levels if ISS were to be scaled back. If the Shuttle program itself were cut back to accomodate a slower launch rate, there might even be savings over OSP and buying more ATVs considering the rapidly spiraling OSP cost since it must be built so quickly.
Plus, if the ISS isn't going to last beyond 2018 or so, which is thirty years since the first module was launched, that would be getting close to the date that Nasa wants to start talking Shuttle 2.0 and before Shuttle 1.X's airframes reach design life (in theory). So, with no destination after ISS to fly to, Shuttle 1.X running cargo anyway, and Nasa repeating their mistake of building a reuseable man-rated medium launcher with no mission the OSP would simply be redundant.
Back to topic...
Right now I don't think anybody knows what OSP will be like, as Boeing is probobly just now figuring out they don't have time to make a giant X-37... and had to slap up somthing. They also have pictures of an Apollo-style truncated cone capsule with OSP written prominantly on the picture. I forsee that OSP will follow one of three design strategies:
-The HL-20 PLS space plane
-The "Big Gemini" of the US capsule days
-The Zarya "Super Soyuz" from Russia
...all scaled down by about 75% for smaller crew loads and less launch mass. http://www.astronautix.com
As far as the new superboosters for Shuttle go, I thought I heard that the air force had a hand in it, but I could be mistaken... I am still not following the logic of building the thing unless Nasa intends to use them... Unless the decision has already been made to build an SDV, and they just haven't told us yet.
Yes so I read... I have mixed feelings about such a move by Congress, which arrre...:
-Congress does not like not being consulted about things that get alot of press.
-Nasa HAS to start preparing to part with Shuttle right now, stay out of O'Keffe's way...
-Congress has a legitmate concern that OSP's costs cannot be controlled, as Nasa has so clearly demonstrated that it has trouble with.
-Congress has a legimate concern that Nasa doesn't know what to do at the moment about their manned strategy. Imparticularly since the ISS and Shuttle are joined at the hip, and Nasa's plans to part them are sketchy at best beyond putting people on OSP.
The RS-84 is a nice engine, though I am not convinced that the current incarnation of Nasa is able to economicly operate any large reuseable craft... A modified Delta-IV Medium or maybe the smaller Atlas-V with two or three single-RS84 flyback boosters would be a nice stepping stone though.
I also am -way p***ed- with Nasa/USAF for building the new 5-segment megabooster SRBs, adding engine-out ability of the SSMEs or an extra 25 tons of payload... and now have no plans to use them on Shuttle!!!
I am beginning to agree with you that a six-man crew on ISS is a little far-fetched, but it isn't rediculus I don't think when they start adding the other lab modules. Making room for two more people should not be a huge issue with the HL-20 or Big Gemini style craft. And if they don't go with a six man setup, thats extra room they can pack cargo into.
As Nasa is painfully aware, the days for Shuttle are allmost over. After launching the last modules of ISS, every launch is another too many. The ESA ATV and Progress-B cargo ferries will not be enough to sustain ISS with 4-6 and do anything useful probobly, so I fear that Nasa will keep on flying Shuttle anyway once or twice a year with a reduced crew. As this would be very desireable to avoid, and ISS would need some kind of CRV with a larger crew anyway, even spending millions for a cargo OSP could permit the penultimate goal of sending Shuttle to the Smithsonian. The biggest issues for ISS at the moment are basic life support consumeables like water and science payloads to have stuff to do. Water is pretty dense, so it will be more of a mass than a volume issue, but ISS will need at least some science cargo, more than Progress-B can haul, so volume could be an concern.
I am wondering, just curious, from a purely logistical POV, is it possible for a crew of three to stay up with only Progress-B and ATV launches?... As far as getting to Mars is concerned though, building a new manned craft would permit crew transfers to a Shuttle-C/Ares/Magnum launched Mars Transfer Vehicle, which will be without a doubt long after Shuttle is gone.
A reuseable launcher would be nice, but unless it leads to rocket able to haul up payload in the 100 ton region, then its too small to get us anywhere but LEO. Building a Mars ship out of 5-meter/20-ton sections on the reuseable stepchild of the EELVs is madness. That being said, OSP has to be finished on a rather short timeframe (no more than 5 years, preferably 3 years, until the CRV is on-station) so building a new rocket is out of the question. Delta-IV or Atlas-V is it.
I really think that limiting OSP to four seats is a terrible idea... if (hopefully when) we increase the ISS crew to six, then we could do away with the six-month-only rollercoaster reentry Soyuz capsules entirely.
Another case for the "big OSP" is that it could possibly become an "American ATV" to ship light cargos unmanned, or if you put the thing on a non-man-rated Delta or Atlas HLV, lift several tons to orbit.
The trouble about fueling decent engines in orbit is that requires a fairly delicate docking operation just so you can come back in one piece, and is not my image of a good idea.
Oh, and for VERY early stage, like a pad abort or in the first minute or two, then a HL-20 could probobly do a RTLS for runway landing.
