Tuesday, August 9, 2011
Most of the other mission designs included some sort of Mars base assets with the first manned mission. This is quite different from what I assumed regarding the nature of exploration versus subsequent activities. So, I pitched my paper as less of a “real” mission plan, and more of a “mine” for different and potentially useful ideas. In part, that’s why it was so well received.
Changes to My Paper (see the 7-25-11 posting not far below)
I did learn some very interesting things, two in particular. One has to do with my alternate for the manned ship’s “hot rod propulsion”. It seems VASIMR is not really an improvement on electric propulsion, just another way of doing it. Its weakness is indeed what I thought: the mass of the nuclear electric power plant required. Its thrust per unit power supplied is just a lot worse than I thought it was when I did the calculations. It’s just not suitable for really fast missions.
The other interesting thing is the notion of a light gas gun for launching hardened payloads into orbit very inexpensively. It should be possible to launch large quantities of propellants and tough hardware for something on the order of $300/pound, if they can be hardened to withstand 3200 gees. This is based on a smaller gun already launching small experimental scramjet payloads for the Air Force at Mach 9. Refueling of my reusable manned ship looks really good in such a situation. Once there is a water mine and propellant station on Mars, the same thing is true for refueling the lander assets left in Mars orbit.
In any event, about the only change I might make in my paper is to replace the VASIMR alternate with a solid core nuclear thermal version, and include artificial gravity and frozen food in the habitat configuration. Its one-way trip time would be 6 to 8 months, and the stay at Mars a little longer than the baseline 16 weeks. The technology development, to be run in parallel with the baseline gas core nuclear thermal rocket effort, would be the artificial gravity habitat. I think a pair of rigid arms out to inflatable living spaces, and spinning the entire T-shaped ship, might work well enough.
Another Interesting Idea
A third very interesting idea is to store and ship hydrogen as frozen water. In this form, it is very strong and so is proof against accidents or mishap. You thaw and electrolyze what you need as you go, which does require power, although solar thermal thawing offers a big help. The oxygen liberated by electrolysis can be used for a lot of things. It takes very little pressure to prevent sublimation of the ice, and a simple sunshade keeps it very cold.
This would apply to chemical as well as nuclear propulsion. Nuclear uses only hydrogen. Chemical uses both hydrogen and oxygen at a mass ratio of 1:6. The ratio in the water is 1:8, so that leaves excess oxygen left over for other uses, even with chemical systems. There is just more available in a nuclear scenario.
A Very Serious Near-Term Problem
Consider: 100% of the humans who ever walked on the moon were Americans, sent there by NASA in its human spaceflight program. 100% of the so-far successful landers on Mars were (and are) American, sent there by NASA in its robotic exploration program. Almost 100% of the probes sent to other celestial bodies are American, sent there by NASA in its robotic exploration program.
The human and robotic programs began together in the late 1950’s; they are synergistic. You cannot successfully do one without the other. Regardless of your opinion of NASA and its effectiveness today, it is the premier entity for the exploration of space, and therefore it is irreplaceable.
Here is the problem: there has been no human exploration target since Apollo ended in 1973. Manned operations in Earth orbit, while essential and even inspiring, are not exploration. We have had men and machines in Earth orbit, beginning with Sputnik in 1957. Going back to the moon is not exploration in the public’s eyes, because “we’ve already been there”. This perception is quite real, even though we didn’t really explore the moon (in the sense of my paper) during Apollo.
The public supports exploration: that is why the probes, the Mars landers, and the Hubble pictures are so popular. Of all the probes and landers, it is the Mars probes that hold the public’s fascination best. This is because Mars has fascinated people for centuries. It is not just the best target for human exploration, it is the only one. Those other near-Earth targets are at best but steps along the way to Mars. (The next destination after Mars is the stars, with the outer solar system destinations but steps along the way.) Reality has nothing to do with perception, and experience says you cannot fight perception.
We have a budgetary and political tsunami about to sweep America, with a great likelihood of doing massive damage to all aspects of all of our lives. One’s politics and outlook on this do not matter, discretionary spending is about to be drastically cut or eliminated, no matter how useful or necessary, for the sake of election politics. That means NASA, among many other things. And NASA has had no viable target or plan for manned exploration since Apollo. A vague “give us X-billion dollars for the next 20-40 years and we might reach Mars” is not a manned exploration program. If the manned spaceflight program is cancelled, the robotic program will eventually fall, as well.
Folks, this cannot be allowed to happen.
It is feasible to send men to Mars right now, with the technologies and hardware we have right now or within the next very few years. We don’t even have to have giant launch rockets. We can do this for under $50 billion, not the trillions everybody out there seems to think it will take. But we cannot do this with the “business as usual” techniques of the last 4 decades, and that includes the way NASA works. Massive management change is required, and that is the hardest part, not the actual flying to Mars.
If you are a space exploration enthusiast, then help get the word out. Technologically we are ready to send men to Mars. And we can do it for a few billions, not multiple trillions, of dollars. The real change required is managerial (and political, not surprisingly).
Tuesday, August 2, 2011
Inner Solar System
The key is going back to fundamentals to figure what we really want out of exploration, then looking at required technologies, given that crew survival, safety, and self rescue are THE paramount design requirement for every single phase. You do that for the most challenging mission (Mars) FIRST, and force every single piece of hardware to be totally reusable.
Exploration and the Greater Scheme of Things
This produces one set of "tinkertoys" that takes you anywhere within range: Mars, Venus, NEO's, and Mercury (the entire inner solar system). Plus, you don't have to keep launching components, just propellants and supplies.
This is my Mars mission paper to be presented to the Mars Society convention in Dallas, August 4-7. A shorter version is posted at http://exrocketman.blogspot.com, dated 25 July, 2011.
Inner Solar System Hardware Designed Around a Mars Mission
Main Asteroid Belt
To go further soonest, we simply upgrade the inner solar system “tinkertoys” with knowledge obtained between now and then. Add a provision for artificial gravity, and either solve the food preservation problem, or add frozen food (which is bigger and heavier). That should make two-or three year trips feasible, most likely limited by the accumulation of cosmic ray exposure. It puts the main belt asteroids and some comets within reach.
The Artificial Gravity Problem As We Know It Now
Giant Planets and Outer Solar System
If a better way to shield against radiation can be devised, and even faster “hot rod propulsion” developed, the giant planets and outer solar system become reachable. It would help greatly to know how to build closed-ecology life support by this time.
At this point, we have to repeat the design process from scratch, because upgrades to the inner solar system “tinkertoys” are no longer feasible. We will know more about what to do when that time comes. The target for design should be the Kuiper Belt, where Pluto is.
I suggest some version of the old Project Orion nuclear pulse propulsion. One must build much larger ships for this: it has the odd characteristic of working more efficiently, the larger the mass to be moved.
Nuclear Pulse Propulsion from 1959-1965 USAF "Project Orion"
A Place To Do the Supporting Work
The kinds of “hot rod propulsion” that we will need to explore these places are very dangerous to develop and test on Earth, because the energy sources for the drives are all nuclear. We need a safe place to test, but it has to be dynamically stable (you cannot test a rocket engine in zero gravity where every test is a flight test).
I suggest the airless, waterless, uninhabited moon. Pick a smaller crater with high ring walls, plant a base adjacent to it, and put the test stands down inside the crater. It’s reachable from Earth without any exotic propulsion at all, and the mildest of the “hot rod propulsion” techniques just makes it less expensive. Perfect!
The last shuttle flight is complete, the orbiters are headed for museums, and thousands are being laid off at Cape Canaveral and Mission Control. There is going to be a hiatus in America’s ability to launch its own astronauts that may continue for a few years.
Actually, I do believe the private companies like SpaceX will fill that void sooner rather than later. I also believe there will be a second, privately-owned, space station up there, very soon.
But, these private ventures, which build upon 50 years’ expertise, will require smaller teams on the ground at the Cape and in Mission Control. Except for local employment prospects, that’s a good thing, because it means spaceflight will become less expensive.
I predict that more than one commercial spacecraft will be flying soon, and that some of our familiar launch rockets will be updated and man-rated to launch them. That’s what NASA’s commercial spaceflight initiative was supposed to achieve, and it looks to me as if it is succeeding.
Here is what we will have: space capsules as taxis to orbit, space stations conducting research and business, and NASA looking outward beyond orbit with men for the first time in 40 years. But, something is missing from that picture!
Oh, yes, the “space repair truck” function of the space shuttle will be missing. Remember it?
It was the self-maneuvering shuttle with the adaptable human crew, that enormous cargo bay as a work area, and that manipulator arm, which repaired so many important satellites, most notably the Hubble Space Telescope.
In hindsight, having to launch that capability in every mission makes less sense than having two or three vehicles like that up there all the time. When you need one, send the crew and some thruster fuel up with one of the new space capsules: same results, far less expense.
All we need is a crew cabin, a space frame about the size of the shuttle cargo bay, that manipulator arm, some thrusters, and thruster fuel tanks.
These could be assembled in place by docking-together modules small enough to be launched by the rockets we already have. This is not a gigantic project, there is no new technology here, just a planned series of launches to regain a capability that we lost with Atlantis’s final landing.
It makes sense to have one in the highly-inclined orbit near or docked to the ISS, one in the more standard orbit eastward from the cape (the kind of orbit Hubble is in), and one in polar orbit to service those satellites. This may not be exploration, but it would certainly be helpful to what we are already doing in space.
There will always be satellites needing repair, and we already have one space station to repair, maintain, and upgrade. We might even use this capability to help build the new exploration vehicles.
I recommend this idea to NASA as something worthwhile and necessary. Maybe some of those laid-off workers could be re-hired to carry it out.
An update to this idea takes advantage of vehicles that have since become available, and also some suit and breathing gas technology that has been forgotten-to-death, about which I have written some articles.
Vehicles already available or available soon:
These include the Russian Soyuz crew and cargo vehicles, the Spacex crew Dragon / Falcon-9 combination, and fairly soon the Boeing Starliner / Atlas-5 combination. There is also Falcon-Heavy and Ariane-5 for delivery of large cargoes to orbit. The Sierra Nevada Dreamchaser spaceplane may also become available fairly soon, as will the NASA Orion.
Suit and breathing gas technology:
The trend to ever-higher suit pressures has produced bulky and constraining space suits. They need not be operated at that high a pressure. There is no reason they could not be operated quite safely at significantly-lower pressures, as detailed in Ref. 1. We did it that way decades ago. Why not do it again?
Given that truth, the spacecraft transferring crew to the repair vehicle could transition from full-pressure synthetic air to a lower-pressure enhanced-oxygen mix, while on the way to the repair vehicle. As discussed in the reference, this could be done with about the same fire risks as sea level Earthly air, based on the chemical concentration of oxygen available to support combustion. Yet, the transition from this mix to a low-pressure pure-oxygen suit would require no pre-breathe time.
Crews riding up and down in the crew transfer vehicle typically use survival-type pressure suits, just in case cabin pressure is lost. Such suits can be used for a short EVA to transfer elsewhere, but are not suitable for doing any real EVA repair work, as cooling capacity is usually absent or quite limited. Physical protection against external hazards is also quite limited in these suits.
Since these repair missions are at most a few days, there is little risk in human exposure to low-pressure enhanced-oxygen mixes. Exposure to pure oxygen is limited to a few hours at a time, that being about the longest duration we can expect of a real repair-work EVA.
Longer term, this is also quite the convenient scenario in which to experiment with MCP suit designs, especially those done as vacuum-protective underwear, with appropriate unpressurized mix-and-match outerwear for thermal, mechanical, and UV light protection. See Refs. 2 and 3 and 4.
The updated figure shows essentially the same features as are in the original. The changes explicitly show the visiting crew transfer spacecraft, the EVA airlock, and some redundancy to the propellant tankage and maneuvering engines. Depending upon the visiting spacecraft, both parts, equipment, and supplies, plus the refill propellants, might be brought up, if cargo capacity permits. If not, the refill operation might be a separate launch.
I have shown a rough guess as to size, based on the old space shuttle cargo bay, and a rough guess for the maximum maneuver delta-vee. The propellants should be storables, to take advantage of refilling techniques already being used at the ISS. They could be the new "green" propellant, if an appropriate oxidizer is available. Monopropellant performance would be too low.
Unchanged are the suggestions for how many such vehicles, and where pre-positioned. One should be at the ISS in its high-inclination orbit. Another should be parked in a low-inclination eastward orbit, to take care of a great many items, including Hubble. A third should be parked in a polar or near-polar orbit, to take care of a great many items in orbits like that.
The fundamental design features are still: (1) a shirtsleeve crew cabin in which to work, (2) and EVA airlock, (3) a manipulator arm (two may even be better), (4) maneuver propulsion sufficient to reach the job site, (5) easy refill of propellants and supplies, and (6) docking capability to support many crew arrival vehicles. The manipulator arm is required to achieve "docked" position control with the object to be repaired, regardless of the forces from moving people and supplies. It also is required to hold the astronauts in position as the apply forces doing their work.
With Hubble having serious failures right now, it is clear that we have lost this wonderful asset, or will lose it soon, if it cannot be "fixed" from the ground. Once it fails, there are but two responsible alternatives: (1) de-orbit the thing to destruction over the ocean, or (2) mount a repair mission and replace the failing over-age avionics. It will be a few years, not months, before the Spacex cargo "Starship" design might be ready to undertake such a mission.
We currently have no vehicle that could capture it and bring it home for repair, or could dock with it and make repairs. There is just not time (or budget) to pursue a massive program to repair it. Yet Hubble really is worthy of repair: the mirrors and corrective lenses are the kind of asset that could be useful for over a century, as have been many ground-based telescopes. It is the avionics and the camera equivalents that need replacing from time-to-time.
There is no need to pursue a long, drawn-out program to come up with a vehicle that actually could make the necessary repairs, nor is there available budget to support a big massive "typical" government program. This has to be done fast, and it has to be done relatively inexpensively. It makes sense to use existing assets to the maximum extent possible.
I suggest these approaches: (1) use an existing craft (such as a Cygnus cargo vessel) to be the basic hull of the crew cabin of the depicted vehicle, (2) use the same manipulator arm that was used on the shuttle and is being used at ISS, (3) use the same tankage, propellants, and engines that were the space shuttle's orbital maneuvering system, and (4) use the same atmosphere hardware that is used on the ISS, but with a reduced-pressure, enhanced-oxygen mix (about 6.2 psia of 45% oxygen diluted with nitrogen). (5) The airlock can be the same as one of the ISS airlock modules. (6) Use the refilling connections currently used at ISS with Soyuz tankers. (7) Pure oxygen space suits can be operated at or slightly under 3 psia (2.8 to 2.9 psia nominal, with a safe-enough leakdown to 2.5 psia).
Only the truss connecting them need be custom-built, and trusses are not complicated! Speed and rapid results are essential, and budgets must be modest. This is not (repeat NOT) the usual NASA program! This cannot be (repeat CANNOT BE) the usual corporate welfare program for "old space". One or more of the "new space" contractors should do this!
1. 16 March 2018, "Suit and Habitat Atmospheres 2018" [analysis of in-lung wet oxygen partial pressures and oxygen chemical concentrations to address supple space suits, adequate oxygenation, elimination of pre-breathe times, and fire dangers no worse than in Earthly sea level air]
2. 23 November 2017, "A Better Version of the MCP Space Suit?" [adding tensioning inflatable capstans to the elastic compression garment concept to create an MCP space suit that is easier to doff and don]
3. 15 February 2016, "Suits and Atmospheres for Space" [definition of adequate wet in-lung oxygen partial pressure for any space suit, at reduced suit pressures, plus illustrations of suits over time, including MCP designs]
4. 11 February 2014, "On Orbit Repair and Assembly Facility" [an earlier article on a potential application of low-pressure oxygen breathing, MCP space suits, into an on-orbit facility for working in a vacuum environment protected from bright sunshine; this facility is more of a repair base than a mobile repair truck]