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What I was suggesting we do--wait to attach the tethers until after the initial course corrections have been made, possibly 2-3 weeks into the coasting stage of the mission--2 spacecraft "flying in formation" until that point.
What this model is suggesting is polishing up the manned EDS of the mission. Much of the original Mars Direct/mars Semi-Direct remains. Just modelling the details in order to use "what we already have." What we have is a figure of 54 ,400 kg to LEO using Falcon Heavy, and according to Spaceflight 101, the upgraded Falcon 9 FT or Falcon 9.v.1.2 can boost 22,800 kg to LEO. I'm not sure whether these numbers reflect just payload or the total mass including the remainder of the launch vehicle?
GW & Robert
I'm just now wondering how many mid-course corrections will be needed, and at what times? It could very well mean that we utilize artificial gravity for only part of the mission. The other thing my architecture allows is keeping the mass of the EDS (Earth Departure Stage) along with a supply of compressed gasses or additional MMH and NTO for this exact purpose, and having the ability to "top off" the landers with same.
We could also simply provide the artificial gravity after say... 3 weeks into the flight after some initial course corrections are made/ Then terminate the AG about a week or 2 before entering into Mars orbit? The bulk of the flight would be with AG, minimizing the effects of prolonged exposure to zero g conditions? Having a bigger EDS booster to give a bigger delta V at the beginning and shorten the flight for gravitational diseases?
I'm just "shooting from the hip" with these ideas trying to stimulate an updated Mars direct model using "what's available now or near time frame."
Another option--transfer development of the SLS to SpaceX for conversion to a landable configuration? I can hear the screaming from Denver and Seattle now! The ballpark low estimate of $400 Million per SLS vehicle launch is probably going to "expand" up to $2 Billion a shot...
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?
Solar power on Mars should be regarded as the backup to nuclear and in the future--geothermal. The original Mars direct scheme published in Zubrin's book called for a 100KWe nuclear plant, but in view of the weight reductions since then, we could suggest sending 2 of them at just a bit over 1 metric ton combined.
The 4 essentials for Mars: (1) Shelter, (2) air, (3) food & water, (4) adequate power.
Even the overly dramatic National Geographic "Mars" series had an episode based on a power shortage brought about by a massive dust storm--and yes, the nuke plant was "offline" due to another inconceivably stupid decision. Duh!
GW-
The concept of Orbital Assembly has some additional merits, especially if done in the vicinity of the ISS. That would placate the ISS supporters at NASA, and get them on board with going to Mars just because their pet project would now seem to be "essential." This way a number of pre-fueled stages could be placed into LEO and simply assembled by docking them together with the Mars spacecraft. This would seemingly complicate the Mars Direct concept, but maybe it was a bit too simplistic as we move forward. Yes, the original concept would still work, but regarding these embellishments as evolutionary rather than revolutionary seems to make sense.
28 years ago, a guy named Robert Zubrin came along and rattled the cages of the established, old order space scientists at Martin-Marietta, and subsequently NASA. Then--the entrenched "old guard" started pulling out the Galactic Cosmic Radiation argument, along with the Bone Decalcification ploy. Cutting edge exploration is NOT risk-free! Did Magellan or Anson do all the risk assessments necessary before sailing around the world? Did Columbus do a risk to benefit study about the chances of sailing off the edge of the Earth before heading West? The hand wringing naysayers seem to have sway in the halls of NASA. The original 7 astronauts all knew they were volunteering for a high risk venture, and there are others just awaiting the opportunity to step forward and risk it all for the adventure, the science, and the growth of mankind into an Interplanetary Species!
Only 20 days on the surface to analyze 5 samples doesn't seem to be a very good return. Limitations in capabilities are there due to the unwillingness to utilize nuclear power for systems and data transmission make this a very poor scientific investment, all costs considered.
As Louis has observed, this is another example of the lack of direction at NASA, and why Elon Musk will be waiting on Mars to pop a Champagne bottle for NASA when they finally arrive 5 years later...
Because NASA is only minimally accountable for the progress on a variety of projects, they simply become "bread and butter" for the engineers and scientists working on them. The error built in to cost plus contracts. Budget X dollars for Y goal; doesn't happen? Engineering group Z is looking for new employment.
It's essentially the difference between selling "research,' versus selling "a product."
NASA needs some New Blood! SpaceX is making them look like a pack of doddering old fools. A new broom to sweep out some of the cobwebs would help, as well as undergoing a period of project rationalization. Too many fanciful concepts that will never progress further than burning up lots of research dollars. Get OUT of the Earth Sciences game that became highly politicized--out completely. Allow NOAA the opportunity to dig their own graves.
That's also what I was thinking when I made the original post.
Not so sure about Io, since it's deep in the Jovian Van Allen belt; not much possibility of a human visit--ever. Same with Europa; Ganymede has some VAB radiation, but a human presence there could work with adequate shielding in a below ground structure sheltered with regolith. Callisto has human presence possibilities--as well as a tenuous atmosphere and suspected below surface H2O. Piggyback several orbiters and landers--nuclear powered?
GW-
Louis and Oldfart1939:
I don't think NASA really wants to take on the Mars mission precisely because it is dangerous, and they have become extreme risk-averse. They have a Bigelow BEAM module on the station now, but are spending over a year just to open the door and go inside. Ridiculous!
It's also why spin gravity has been largely ignored by NASA management: microgravity disease is an excuse not to go. Just like galactic cosmic radiation exposure is brought up again and again as an excuse not to go. Solar flare radiation will be brought up as a reason not to go if the other two are knocked down. They will finally use confinement/insanity as the reason not to go: the crew needs space, which requires a big vehicle, and that is expensive (based on SLS costs and availability, not commercial launchers).
GW
It is spot on the real reason; also the reason Elon Musk has engineers in their late 20's and early 30's working for him. He isn't risk adverse to a stupefying degree!
GW-
The dynamics of rigid spinning bodies has been well understood for well over a century now. We're really good at it. Balancing tires on cars is one application of it. Balancing gigantic steam turbines in power plants is another. And don't forget about propellers and windmill blades.
GW
This is precisely what Wernher von Braun understood back in the 1950s in his wonderful Collier's magazine articles!
GW-
I'm liking the way you're thinking about the topic. If we CAN do orbital assembly, launching modules easily hooked together in LEO would seem to be the way of the future. Even the crew-rated Dragon 2, which is being designed for a crew of 7 to the ISS, would be an integral segment of the system.
As you stated, the original Mars Direct was conceived with 1980s hardware and capabilities. Maybe a revised, expanded, and updated model could be developed?
Here's a link to the Spaceflightinsider's article regarding the proposed Europa Lander, and it contains a short video worth watching.
Robert-
What we want MOST of all is for a SUCCESSFUL mission. What we're doing here is brainstorming all the options and trying to poke holes into the weak points of the ideas. It's just like the folks at NASA wringing their hands about exposure to Galactic Cosmic Radiation! Sure, we can go with a 4 man mission, but that's the minimum. A 3 man mission is getting pretty "lean" w/r to science goals which can realistically be accomplished. If we're trying to hold things down for weight allowances, but with adequate internal backup, then try for a crew of 5 instead of 4. With a 4 person crew, physical and mental exhaustion will become a factor, too.
The only conceptual problem I can see in the Zubrin "tether" system is it's increasingly awkward the larger the system becomes--that is--the larger spacecraft will become in the future. The effects seem to be cumulative under prolonged absence of gravity, and returnees from the ISS after only 3-4 months seem to be minimally affected. I'm all for having a brainstorm session; however the Ridley Scott Mars spaceship Hermes looked pretty interesting. Just how well it would function under strong acceleration--that's a big structural question. Probably NOT very good. The Martian combined the "cycler" concept of Buzz Aldrin with much of the Mars Semi Direct scenario of Zubrin. Before I became affiliated with this group, I was thinking of something along the lines of a semi-rigid structure between two sections of the Mars vessel, sort of the GW Johnson model. If NASA gets too deeply involved in the biochemistry and hormonal regulation area where I've spent a large part of my professional career, it may be another 50 years before they are ready to "venture forth where no man has gone before."
When one starts "wargaming" various scenarios, it's simply inevitable that something gets overlooked. The Rover should have a powerful winch with say--100 meters of light aircraft cable on the spool. The suits should have attachment D-rings integral to them, and in a variety of body locations. Then--the rover should have a wireless remote drive controller in order to command the rover to start a winch and enable a bod haul up and out of a bad scenario. The Rover should actually have 2 winches; on at the front and one at the rear; this could, in principle, drag a stuck rover out of a sand trap. Needless to say, the proposed Rover and crews will need some serious desert training time and doing some injured crewperson evacuations.
I'm not trying to be a Negative Norbert here, just a realist. Just make plans and train for the worst possible scenario and in reality it will probably be even worse. At this juncture you ARE getting some input from an ex military version of an EMT.
Gravity on Mars is ~ 40% of that here on Earth, which should keep the hormonal control system functioning pretty well. In hindsight, the ISS should have been built to the von Braun "bicycle wheel" model wherein the numbers of gees could be varied for experimental purposes. Why NASA overlooked that possibility astounds me.
GW-
I am in total agreement that the solution to all the observed signs of degenerative disease are alleviated by artificial (centripetal force manufactured) gravity, and would appear to be a requirement for deep space journeys. Other than Robert Zubrin, who else has addressed the issue in such a straightforward manner? Certainly not NASA, not Elon Musk. The Hermes spaceship in The Martian did---much to my appreciative surprise. I'm sure that after the biochemists address the problem, various pharmaceuticals will be able to somewhat attenuate the bone decalcification problem through hormonal manipulation, but that is symptomology. Treating the symptoms and not the underlying problem which is best addressed by provision of some artificial gravity.
One cannot underestimate the potential for serious injuries in unknown terrain, and one rescuer is totally inadequate. Period. A serious injury situation on Mars has one real potential: things will get worse before they get better. Too many of the planners for missions do NOT have adequate experience on the ground to appreciate this. I'm not going on the movies, either; injury accident scenarios tend to evolve into a cascade of head to tail events making things nearly overwhelming. The smallest fully functional group devolves down to a group of 3; in a bad situation, one person of the team rest or sleeps; one other member does essential tasks, such as food preparation or equipment maintenance; the 3rd remains "on alert" for changing condition, or maintaining communications with a higher headquarters.
This brings to mind something for the spacesuit design. presence of a special patch with an auto-sealing injection compound, just in case an injection of morphine, or other lifesaving medication needs to be administered.
I'm making these observations based on my 3 years of wearing Army Green as a medic in a variety of situations. I was also deeply involved with the Rocky Mountain Rescue Group based on the University of Colorado Campus in Boulder after my military experience. Believe me, I know about bringing someone down a near vertical rock face or on a steep scree slope. T'aint easy.
Lighter suits...yes! But before you think about picking up and carrying someone for even a short distance, consider the totality of the injuries. This assumes that the injury occurred on a nice flat and easily accessed spot. More likely, it will be a fall down a steep slope caused by bad footing; assume one thing: it will be in the worst possible place for a casualty evacuation. Remember: Murphy was an optimist. I learned every conceivable method of carrying a person injured at Ft. Sam Houston, Brooke Army Medical Center. More than likely it wont be a nice easily splinted arm or lower leg, and will probably have back or neck complications. By planning for the worst possible scenario makes us prepared for whatever comes along. A Stokes-type litter could be hauled up a steep slope by a winch on the rover, but putting a seriously injured person IN the litter is the problem, and one person cannot do it. Every person I ever worked on was thinking "well, I'M not going to get hurt...." Not trying to rain on anyone's parade here, Robert, but even careful people get hurt due to unanticipated circumstances. My crew plan of 7: 1 team leader; 2 Triad leaders and two triads. This has a definite pyramid structure, but ensures cohesive performance at all times.
Uhhh....you can have MY share.
GW-
It seems that Ridley Scott too, understood the gravity issues when he directed "The Martian?" The Andy Weir book was great, but the concept of incorporating the wheel design into the Shuttler-Type spaceship was frosting on the cake! They combined Buzz Aldrin and Elon Musk to arrive at a reasonable solution. One way of addressing this problem is gaining a better understanding of the underlying hormonal changes induced by zero G or microgravity. That's probably MY field where I can make the greatest contribution. This is another area where the deep space research will ultimately have an Earthly payoff by gaining a better understanding of post menopausal osteoporosis. One of the current treatments for Osteoporosis utilizes a pituitary hormone, Calcitonin; this is a regulator of calcium uptake, and it's been shown to be quite effective. Patients get periodic injections of very small quantities of this hormone which speeds up incorporation of Calcium into bone tissue. The real issue is a bit deeper, and that involves the stem cells involved, known as Osteoblasts (bone replacement cells) and Osteoclasts (bone erosive cells). Both are produced, but in osteoporosis, the Osteoclasts seem to have the upper hand and bone tissue is degraded faster than the cells are being replaced. What's needed is identification of which growth factors accelerate Osteoblast formation, and attenuate Osteoclast production.
One way to get a reactor into orbit is through use of Thorium as the radionuclide. This isn't a "bomb in orbit, or a bomb in space." We had a Thorium critical mass nuclear reactor on the University of Wyoming Campus back in the 1960s. Naturally the tree huggers had it shut down and dismantled in the 70s.
Titan's atmosphere is too dense for any sort of photographic reconnaissance mission; it would need a Nuke reactor to do a radar surface mapping, and for data transmission. I'm opposed to doing anything with one of the exotic propulsion systems due to very low thrust produced. We need to get a Nuclear thermal system running AGAIN! The NERVA back in the 1960s was well suited for outer Solar System exploration. It has an Isp of 900 seconds, versus H2/LOX at maybe 450 sec. That way we could get a lot bigger delta V, especially after a slingshot around Jupiter.
A mission to the Jovian moons is one that I would like to see, followed by one to the Saturnian moons.