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I haven't written much on this topic as yet, so here goes. I like the concept of a rigid structure connecting the spinning modules, but how to accomplish such without incurring an unacceptable amount of mass which has consequences through the tyrannical rocket equation. First question to pose is what's at either end of the spinning mass structure, and how far apart must we make them in order to avoid Coriolis effects of induced nausea, etc. One way of getting sufficient parts into a trajectory towards Mars is by employing a "convoy" philosophy in the initial stages of exploration. The first vessels will be small, so we'll need something to carry necessary cargo and equipment. I'm going to suggest we send a group of 3 vessels, maybe even 5, in a "Convoy." One vessel, possibly larger that the others (also unmanned) becomes the central "hub" of this rotating structure. It has 20 meter tubular "passageway" elements able to fold out sideways from it's center. These should be lightweight but strong reinforced carbon fiber structures. These should be connected as hinged elements capable of deploying from the hub some 60 meters in either direction from a 10 meter diameter central structure. Employ 2 smaller modules each with similar fold out tunnel structures, each one adding another 130 meters of "passageway." The 2 crewed ship elements in the "convoy" could be carrying a similar single 40 meter element in their cargo trunks. These would be attached at the docking hatches atop the capsules. All added together, we would result in a semi-rigid structural element allowing passage of crew members to the central supply hub and transfer between the 2 primary spacecraft, and allowing controlled rotation at a low rpm to develop some centripetally induced artificial gravity. At the end of Hohman transfer trajectory, the tunnel, or passageway structures are discarded and the 3 or 5 vessels make atmospheric entry. This obviously doesn't solve the problem for the Earth return, but keeps the Mars crew in excellent and functional condition. As a backup feature, all these units could have embedded in the carbon fiber structure a strong aircraft grade cable, should any one module be damaged.
Louis-
I like using PV, but not as the mission's primary power source. They are great, but since Mars has an approximate 24+ hour diurnal cycle, another component of mass is required: batteries. Batteries are heavy, so there goes a lot of our mass transportation budget! My ideal nuclear plant would be Thorium based, as the fission by-products have shorter half lives and could simply be buried--or loaded onto a return spaceship and flown into the Sun. I'm a "belt and braces" kind of guy; never putting all the eggs in one basket, so to speak. Need BOTH solar and nuclear. The 300 We RTGs simply don't make enough contribution to the overall energy scheme to even be included in calculating the total energy required by the Mars Station1.
SpaceNut-
I am in complete agreement with that sort of approach. I'll enumerate below what's really necessary--beyond the transportation to and from the planet.
(1) Shelter and protection from a hostile environment. Includes both adequate space suits and habitat.
(2) Breathable air supply, scrubbed for elimination of harmful gasses.
(3) Water. Required for drinking, food preparation, and sanitation.
(4) Food to the extent of provision of adequate calories and all other micro-nutrients (minerals, vitamins, etc.). Should be palatable.
(5) Power. For heating, running oxygenation apparatus, water reclamation, light. Production of O2 and electrolysis of H2O. Methane production.
(6) Transportation. Should be multipurpose, with front loader for moving heavy loads and digging, moving of regolith, construction.
The very first SpaceX Red Dragon vessels will give us an indication of what can be taken along. Forget the unobtanium items. Stick with solar arrays and a small but efficient nuclear power plant. Moxie unit for production of O2 from the CO2 atmosphere. Tracked and fully enclosed Bobcat with both front loader and auger drill bit. Can't go wrong with stockpiling food.
Astrophysicists are hopeful the James Webb Space telescope will be able to delve deeper into the atmosphere.
Styrene? NOOOOOO! This could readily thermally polymerize in the cooling lines! This stuff is the WORST possible choice. Also, as an aromatic hydrocarbon, is very prone to coking. Oxygen is actually a polymerization inhibitor. The final 15 years of my professional career were spent synthesizing various substituted styrenes.
The density of these fuels is a disadvantage. The Isp is OK in both cases, but the Id is low. Need bigger (and thus, heavier) tankage for a given amount of Enthalpy.
Of all the available fuels possible in use, my choice would be either Aerozine-50 or MMH. High Isp, and without the need for pressure or cryogenic storage. The real problem is the cost; not so much of it's manufacture, but through the implementation of EPA regulations. It's a transportation issue--not a manufacturing one. The combo of MMH and LOX is pretty good.
GW-
In my opinion, RP-1 is at best, a compromise. It offers ready availability and a low cost. Unfortunately it's a petroleum distillate, that undoubtedly contains traces of sulfur-bearing compounds which are ultimately responsible for coking. Methane, at least on paper, would be a much better choice as a fuel until the secondary issues are considered. These being, it's (1) a modest cryogenic fuel, and (2) requires larger tankage in the vehicle due to lower density. Rocketdyne attempted to address some of these problems a few years back by experimenting with 1,2-Diethylcyclohexane. They apparently abandoned it--I suspect due to the considerably higher cost relative to RP-1. It would be better in many regards to RP-1, since it's a synthetic by necessity; the Enthalpic density is comparable to RP-1 but without some of the refined fuel's drawbacks, such as gelling at low temperatures, and undoubtedly less coking.
For these electric thrusters to become at all useful, the thrust needs to increase by several orders of magnitude, while the mass of vehicle decreases by a similar scale. 20 Newtons isn't much thrust. The mass is huge, and even though the thrust is ongoing, it will have an abysmal acceleration.
I've been quiet here, but everyone should read Robert Zubrin's comments, entitled the VASIMR Hoax, in his small volume "Mars Direct." Currently available in Kindle format at Amazon.com.
"VASIMR...is neither revolutionary nor particularly promising. Rather, it is just another addition to the family of electric thrusters, which convert electric power to jet thrust, but markedly inferior to those we already have."
Robert Zubrin, in Mars Direct.
The European Southern Observatory just reported the detection of a possible exoplanet atmosphere in Astrophysical Journal. The planetary system is identified as GJ1132b, and the atmosphere was detected by measuring the dimming of light at 7 different wavelengths during transit across the stellar disk, where one wavelength showed a larger planetary diameter than the others; with a conclusion drawn of atmosphere not transparent to the wavelength. Initial composition is thought to be a combination of methane and water vapor.
Yes, but Lithium is necessary for production of Tritium, which is the other component of the basic fusion reaction. That in itself requires a fission reactor for it's production. Yes, it would be nice to have a fusion reactor, but don't hold your breath. The He-3 on the Moon is also a useful commodity--once we get a fusion reactor working.
Actually, the USAF is probably more helpful w/r launch facilities. NASA for deep space tracking.
Musk has a rare combination of a vision and necessary capital. He's essentially able to "look beyond his next paycheck" in order to make plans. I've absolutely no faith in NASA's ability to make the necessary contributions to visionary exploration, but will continue to consume and distribute money to the "old space" companies. It's become a self-consuming logistical tail.
According to the launch manifests published on both SpaceflightInsider.com, and also on Spaceflight101.com, the crew Dragon launch abort test is going to occur in late July, in addition to the Falcon Heavy demonstration flight. There's also a second, payload carrying Falcon Heavy flight, scheduled in November. The crew Dragon demonstration flight is also scheduled in late year. If only 2 of these 4 missions are carried out, it would mark enormous progress towards the circumlunar ballistic free return flight with paying passengers in 2018.
The Blue Origin video is somewhat optimistic-insurers would probably demand the passengers all wear suitable head protection in the form of lightweight hard hats.
Please recall that methane requires 3x it's mass of oxygen for combustion. Nuclear is the ONLY safe backup to solar--at least in the early stages of settlement. The SAFE-400 system appears attractive at this point in time. It will be entirely inadequate once any type of manufacturing is started. RTGs simply don't have adequate power for what's needed, but could have several strategically located for emergencies. The ultimate reactor should be Thorium based, and not Uranium.
Major sandstorms are a common phenomena on Mars, rendering reliance on a strictly solar power supply very unwise. The two systems should be complimentary, capable of providing abundant power to the initial research facility and associated agricultural endeavors.
What's being discussed here is the magnitude of second-order effects to the basic thermodynamic calculation. Yes, in principle, the utilization of the "wasted" heat will very slightly reduce the efficiency of the Carnot cycle, but the benefits in doing so will be significant. Using this dumped heat to warm a greenhouse during the Martian night will be offset by the gain in foodstuffs produced as a result. I also suspect that the reactor will be somewhat over-engineered to produce the desired Wattage regardless of what's done with the radiated heat.
According to the published launch manifests on Spaceflightinsider.com, there are at least 2 Falcon Heavy flights scheduled this year, along with the Crew Dragon demonstration flight; that's in addition to the Crew Dragon launch abort demonstration. There have been rumors circulated on many of these space sites, hinting the use of previously flown first stages as boosters for Falcon Heavy. This should be giving the management at Boeing and Lockheed-Martin ulcers!
P.S. NASA and ULA both need some embarrassment; it's good for their collective souls. A dose of entrepreneurial reality!
My question for these researchers is: do they have any clues to the present intensity of Solar wind as opposed to that earlier in the Sun's lifetime?
Some new results have been published from the MAVEN satellite studies about Mars' atmosphere--pas and present. The conclusions reached in this paper are --discomforting for those of us wanting to colonize Mars.
Trump's comments regarding NASA reauthorization act, Hubble Space telescope, and the James Webb telescope.
When doing this sort of speculating about efficiencies and utilization of "waste heat," it helps to define the system to which these calculations are applied. Does the system end with the steam pipes and condensate collected, or continue on outside the immediate reactor as some have suggested here. Taking a view that's too restrictive means simply letting 300 KW escape. Yeah, utilization for greenhouse heating might degrade the efficiency of the power generation a small amount, but the tradeoff is lots of heat for gardens. I think once the steam or other circulating medium has condensed, we end the Nuclear Reactor calculations at that boundary and call it a "system." This sort of cutoff is how most thermodynamic problems in Physical Chemistry are handled, otherwise the calculations aren't really possible.
SpaceX again amazes the industry by re-flying a Falcon 9 to launch SES-10, while again recovering the once-used first stage. Go, SpaceX!