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Robert-
There is definitely an update by Zubrin IN PRINT, and available through Amazon; it's entitled "Mars Direct;" it is a small paperback update to his thinking. Some have criticized it as being something of an anti NASA political rant, but it does contain some thoughts about use of Falcon Heavy and SpaceX involvement. I personally recommend it.
Using LCH4 is fine, but the density is still fairly low, requiring larger tankage than--say--MMH. The combination of vacuum engine performance as stated by Musk for the new raptor engines is very good, though. The big imponderables are the freezing properties of various fuels and a stay on the lunar surface. LH2 is definitely NOT going to freeze into a lump in the tanks. I haven't checked the various melting points of the fuels, other than to say RP-1 is a total no-go.
I believe that Robert Zubrin, in his latest iteration of Mars Direct, alludes to bringing return fuel and only producing LOX on the Martian surface? Not sure whether he advocates RP-1 or LCH4? Either way, the LOX represents 80% of the propellants needed for the ERV.
SpaceNut-
After reading the article listed in your previous comment, Robust Lunar Exploration...Existing Upper Stages, it struck me that use of LH2/LOX is very seductive, but brings many problems to the table. And what has really happened, the dramatically reduced cost per launch to LEO brought about by reusability changes the entire paradigm. LH2 has a great exhaust velocity and hi Isp, but is offset by a very low density requiring larger and well-insulated tankage. My argument to all these other proposals is--live with the non cryogenic MMH and NTO, use more physically robust hardware, and simply offset the weight penalties by using cheaper heavy lift to LEO. Maybe my approach is too "brute force" for the geniuses at ULA and NASA.
SpaceNut--
In an edit, I added in the development of both a Sabatier reactor and a Moxie system, along with the technology for storing their products.
Robert-
You're on the right track. But what we probably should do is make a set of lists--3 of them; first, what is available NOW; second, what is already under construction and due for completion, and finally, what do we still need to develop. Regarding what we need to develop, I don't mean entirely new heavy lift vehicles, or entirely new from scratch components. Use existing hardware capable of some major redesign/alteration to suit our purposes.
Available now:
(1) 100 KWe Nuclear powerplant.
(2) Falcon 9 v.1.2+.
(3) Dragon 1 cargo version.
(4) Dragon unpressurized cargo trunk.
Available near-term:
(1) Falcon Heavy, upgraded to Full Thrust.
(2) Dragon 2, Human Rated spacecraft.
(3) Red Dragon Mars landing rated.
Need to be developed:
(1) Living quarters-expanded cargo trunk for Dragon 2+.
(2) Earth Departure stage, modified from Dragon trunk sections.
(3) Mars landing stage with extendable legs.
(4) Mars habitat stage, prepositioned on Mars with transponder system. Includes prefabricated "hard wall" habitat & airlocks.
(5) Earth return strategy and hardware.
(6) Sabatier and Moxie reaction units and storage technology for products.
Now we get to the interesting part of the discussion. Do we use the modified Mars Direct plan, with an orbiting ERV, or do we do a straight Mars to Earth ERV? How long do we stay? How big a mission? How big a rover do we need (versus "want")? How many prepositioning cargo missions do we need? What strategy ISPP do we adapt? Until we have an assessment of what's available now and in the pipeline, this is all an exercise in futility.
One of the other possibilities for an unmanned mission would be establishment of a GPS satellite constellation around Mars. Now there's a good goal for the folks at NASA! Unlike you, I'm not really that keen on the sample return missions, as they seem to be very pricey for a minimal return on the investment. There is also an extremely high failure probability, which means risking too much of the NASA budget--putting too many eggs in one basket.
SpaceX's success is based on the combination of GPS satellites and ground based transponders, so that's the direction I would choose to follow with mission planning.
Prepositioning of landing transponders was an integral part of the original Mars Direct plan which was presented in the Mars Underground movie.
The accuracy in landing is actually based on the GPS system available to the computers, in addition to some carefully placed radar transponders at the landing site. On Mars, we don't have that system in place, but after a single Falcon is there equipped with a single transponder, we are in lots better shape for landing in close proximity.
In my post #4 above, and especially in he second quote box, I have addressed most of these points. Artificial gravity? Yes. Larger size vehicles? Yes. Prepositioned ERV? Yes.
Take a look at my post #56 on the SpaceX, NASA, and the New Administration thread; the utilization and/or modification of existing or already proposed hardware should be combinable into a Moon vehicle system.
Proposed architecture: Dragon 2 capsule initially modified for an Apollo 8 redux with increased food and consumables simply by lengthening the capsule. Convert the trunk segment into a booster stage with enough fuel to undertake Moon orbit insertion and orbital departure on a return trajectory. Have an in-orbit assembly of an Earth orbit to lunar trajectory throwaway booster. Could in principle, become a technology demonstrator for the tether system of artificial gravity production? This system could utilize the surplus crew capacity of 7, scaled back to 2-3-4 astronauts in order to conserve oxygen and consumables.
For the Apollo 11 redux, lengthen the trunk stage(s) to include a lunar landing motor, fuel supply for landing in a separable stage that could be left behind with landing legs, etc. The other trunk stage would contain a motor and fuel for lunar departure. The Dragon capsule would have the 8 small Raptor engines and MMH/NTO fuel for an Earth landing. This whole system is again, built at the ISS, thereby making the boys at NASA's eyes cross with ecstasy. This only tasks SpaceX with building the intermediate stages modified from the currently unpressurized cargo trunk.This whole system isn't some multi-billion dollar wet dream. Just a rationalization of existing capabilities.
Abstract out the word "moon," and insert "Mars" in the above. Modification of several of these trunk stages, assembled in orbit could--in principle--build a Mars landing vehicle.
When brainstorming, we should regard NOTHING as "set in stone," and be looking at alternative pathways to the same result. If, with the existing hardware (Falcon Heavy) we are limited to the payload fairing Diameter of 5 meters, do a redesign based on those parameters. The other one being 53 metric tons to LEO. Moving forward from these limitations shouldn't be insurmountable. As size increases, the tether concept increases in scope, too.
I've been conceptualizing something based on the existing components and several which could be constructed in a reasonable time frame. My design encompasses having several functional modules constructed specifically for in orbit mutual docking/assembly.
Component (1) would be an expanded and uprated Dragon 2--maybe called a Dragon 2+, with a base diameter of 5 meters. It would be capable of docking at the ISS through the docking adapter already designed. It would have a removable heat shield which will not be needed any longer , but was in place to protect the vehicle and crew in event of a launch failure. In place of the unpressurized cargo trunk, a separately launched crew quarters and supplies module, module (2) would be joined and bolted to the crew capsule. To this, a 3rd module--Mars landing module (3) would be attached, containing the engines and fuel/oxidizer components (I'm suggesting MMH and NTO for long term storability). It would be equipped with landing legs in a manner similar to the Dragon 9 v.1.2+ currently made. Finally, an Earth departure stage powered by cryogenics--a methylox combination using the new raptor engines. This would be flown to orbit immediately prior to ED. I'd err on the plus side by building 2 of these vehicles and having them both depart at the same time, then accomplish an in-flight maneuver to join together with tethers for production of artificial gravity at 0.5 Earth, just in order to maintain some extra strength at Martian 0.38 g. At Mars arrival, they would de-spin, cut the tethers and aerobrake into mars orbit. They would land sequentially several hours apart. Each vessel could in principle carry a crew of 7, but would use the capacity to carry 4 or 5. At Mars, that would give us 2-3 Triads and a mission commander at a total of 8 or 9--or 10 if a backup member is thought warranted. All of this would be preceded by sending the supply, nuclear reactor, and habitat structures, in addition to an ERV.
This is just my first "draft" of a proposed mission. The ERV would definitely be ISPP powered, and the large combined crew size would allow for some to stay on Mars for a longer time frame--an additional 18 months for the next Hohmann transfer window to open.
Yes, this mission architecture is not the minimalist model, but could be accomplished with 4 Falcon Heavy and a couple Falcon 9 v.1.2+ flights. Since all are to LEO, re-landing the booster stages at Canaveral should be possible. It also allows for this to be done over several months for all the in-orbit assembly to take place. Some of the cost could be offset by carrying some supplies to the ISS, as well.
Just a note: The affordability of this concept is made possible through reuse of recovered booster stages, and my estimate of overall cost is under $500,000,000. Or a Half Billion. Call it the cost of a single SLS?
Next News Network is actually the #1 ranked "alternative news" site on the Internet; the most actual views per week, better than CNN and Fox combined. They aren't prone to BS.
Back to the Moon? I just saw this on YouTube:
After perusal of the history on various Mars Mission topics, I thought that perhaps a new thread would be in order, wherein we can concentrate comments/criticisms of previous mission architectures from a 2017 viewpoint. Back in 1990 when Zubrin and Baker first postulated MARS DIRECT, especially in light of the disastrous "90 Day Plan," it was a tremendous breath of fresh air and thus was very exciting. A lot has happened in the intervening years and some of the tools now available simply weren't.
To briefly summarize what's now possible that was not possible, or at least, had not yet been demonstrated: Reusability, and possibility of Orbital assembly of subunits. Include in this: weight reduction and availability of portable and powerful Nuclear reactors. These all are capable of dramatically reducing the cost and some of the complexity of a Mars Mission.
We now have, thanks to Elon Musk and SpaceX, reusable orbital heavy lift capacity. We also have the completed ISS capable of berthing both supply and crew capsules. We also have some COMPETITION for Boeing and Lockheed-Martin. We also know that water in some form or other, is actually ON MARS! All of these components should allow an updated and more refined approach to doing the first mission to the Red Planet. We even have the Dragon 2 capsule which is designed not only to fly up to the ISS, but also return astronauts back to Earth along with substantial mass of experiments and wastes to be disposed of.
As Robert Zubrin has constantly stated, for an actual manned mission to take place, it must happen within an 8 year window or less, due to the way political winds blow. So...my challenge to this group: build a mission from existing or relatively easy to modify/upgrade components! In another thread, (one of the Apollo xx Redux threads), I suggested using an orbitally assembled system based on various components within the SpaceX product line--a "mix and match, or 'Tinkertoy' " system. And--everything based on the fairing diameter of 5 meters from the Falcon 9/Falcon Heavy system.
This is a blank sheet of paper. Let's all go for it!
Robert-
Indeed; bringing LH2 from Earth was part of the Sabatier Reaction proposal by Robert Zubrin as one of the key points in Mars Direct. The entire concept of smelting Iron and manufacturing Steel will undoubtedly be in a second generation of missions directed towards true colonization.
We've just about reached the limits of what Robotics can really accomplish. We had a discussion at the Colorado Front Range Chapter of the Mars Society just this past Monday about the next scheduled rover; turns out the sample caching system for later sample return is the one causing the most headaches to JPL and it may delay the mission by one Hohmann Transfer Window, to 2022 instead of 2020. The concept of sample return done by Human missions is as probable as one done robotically. The Red Dragon will likely fly in 2020, not 2018, so that gives a bit more time for payload planning and design.
I consider the samples CAPABLE of being returned are of minimal scientific interest. We really need samples obtained by a core drilling system capable of going down at least a meter to obtain material not subjected to eons of UV exposure and Cosmic ray bombardment. But...that's just an old laboratory chemist doing the talking.
Robert-
My above post #9 simply pointed out that CO would be available in XS from the "Moxie" unit being proposed for the next Mars Rover which "may fly" in 2020. In order to use additional Hydrogen, a reclaimable source of water must be found for electrolysis first. Bringing LH2 from Earth would be inconceivable to me.
Although I'm not the expert that GW Johnson is on this, my extensive chemistry background comes into play on the topic regarding fuel combinations: RP-1 is difficult to use on long missions due to the deep space environment of extreme low temperature. RP-1 undergoes a viscosity increase below -7 Celsius, that makes it unusable. LH2 has it's own issues of being super cryogenic, low density requiring larger tanks, and lots of insulation. LCH4 is fairly compatible with the requirements for Mars landings, as are Monomethyl Hydrazine and Nitrogen Tetroxide ( MMH and NTO). They are not "problem liquids" but DO exhibit extreme toxicity. This couple has adequate Isp and exhaust velocity for deep space missions, as well.
If we are using the apparatus sent to produce O2, the by-product is also CO, a "reagent" found in the Blast Furnace equations for manufacture of iron. It could also be used in production of carbonyls and purification of other metals. If we're producing metric ton quantities of LOX for the ERV, there will be even more CO produced. Why waste it?
I don't know enough about 3-D printing to suggest the use of metal carbonyls as "ink" in printing metallic objects.
Entry angle determines attitude; the drogue chutes are principally used to decelerate the vehicle. It's conceivable the Mars Red Dragon could have larger propellant tanks than those for reentry from ISS? They currently are rated at 1900 kg capacity, and a separate tanks of both MMH and NTO. As these are NOT cryogens, weight savings obtain through NO insulation required.
GW-
The tether was part of the original Mars Direct proposal by Robert Zubrin. It's light, inexpensive, and gets tangled easily. ;-)
Perhaps the new administration will move away from Cost-Plus contracting, which only encourages cost overruns and glacial progress?
I'd really like to see the Trump Administration publish a request for bids to accomplish both the Apollo8 redux and the Apollo 9 redux, both on completion-oriented contracts.
SpaceX is very clever; incredibly open about big ideas and goals, but very secretive and tight lipped about the details. But...their accomplishments speak volumes about competency. The latest news from the mouth of Gwenn Shotwell is slightly discouraging, in that Red Dragon may not be realistic in 2018; they already have lots on their plate, ranging from a huge flight manifest backlog, to preparations for the maiden flight of Falcon Heavy this year. Ms. Shotwell stated that by deferring the next Hohmann transfer opportunity, a great payload for Red Dragon could be ready in 2020's launch window.
By the way, welcome to the Forum; I'm kinda' one of the new kids on the block myself.
GW-
You may wish to revisit your source for the Ganymede escape velocity, which should be similar to that of Callisto; Ganymede is slightly larger (diameter), but slightly less dense, and only a tiny bit more massive. Their gravity relative to Earth is around 0.12 to 0.14 Earth G.
SpaceX was recently criticized by the Government Accountability Office for delays in the manned Dragon capsule, and called into question whether the company would be able to meet the late 2018 manned flight requirement. SpaceX COO, Gwynn Shotwell replied: "The Hell we won't."