Lunar Distractions

14 Responses to Lunar Distractions

1. DougSpace says:

   April 20, 2015 at 12:20 pm

   I would add a few things things to this article. First is to note that the Moon is a legitimate destination in its own right which we should be going to independent of any plans for going to Mars.

   Second, missions to Mars may also need a significant amount of shielding for radiation. The Moon can be an excellent source for that.

   Finally, “going to Mars” can mean a few of things:
   – Doing a Mars flyby mission,
   – Doing a Phobos-Deimos (PhD) mission,
   – Doing a Mars exploration surface mission (aka “flags-and-footprints),
   – Establishing a permanent Mars base.

   I believe that we can do the first two without needing propellant from the Moon. So I advocate a parallel strategy in which we first take a couple of real steps towards Mars while simultaneously establishing operations and a permanent base on the Moon. Then, when we are ready to go to the Martian surface, the Moon can help that effort. The end result would be a sustainable foothold on both worlds.
2. Michael Wright says:

   April 20, 2015 at 12:57 pm

   Ugh, I find reposting my same opinion (here goes again). Reason everyone talks about Mars and not the Moon is because if the Moon is the goal then hardware will need to be built now (i.e. someone will have to spend money now on contracts for a lander and a earth transfer stage). Building hardware is expensive. Design, build, test, experience failures, work out the bugs and kinks, re-design, argue with people where the faults are, take a beating from the press “you guys can’t get anything to work,” pull a lot of all-nighters, have to come up with additional funds for OT and/or getting new hires to help.

   But if the goal is Mars, then you can put off on building hardware 20 years into the future (and it has always been 20 years for the past 50 years). In meantime basic research and studies (minimum costs) can be continued regarding longterm effects of microgravity and radiation exposure (nothing wrong with that as there is probably much still to be learned on how to mitigate such environment). But when talking about going BEO, it is kicking the can down the road to some other smucks into the future that will have to spend money for hardware.
   • Joe says:

     April 20, 2015 at 6:19 pm

     Do not feel to bad about having to repost your positions on this subject.

     At least, it keeps me from having to say the same thing.
3. Grand Lunar says:

   April 20, 2015 at 3:14 pm

   We need new leadership that is open to the idea of using the Moon for these logical reasons.

   And as you have indicated previously, we also need to stop with the “Mars is the goal!” mentality.

   It is past time for a different way of thinking.
4. J Fincannon says:

   April 20, 2015 at 4:10 pm

   An assumption is that the “slow boat” to Mars is propelled by H2/O2 fuel. If it is powered by Xenon and SEP (albeit very large SEP), then getting the fuel from the Moon doesn’t help as much. I think there were some possible SEP fuels that might be available from the Moon though if they want to invest in making the thruster.

   Magnesium works and is available in lunar regolith (6% in the form of MgO). Szabo, J., Robin, M., Duggan, J., Hofer, R., “Light Metal Propellant Hall Thrusters,” 31st International Electric Propulsion Conference, IEPC Paper 09-138, University of Michigan, Ann Arbor, Michigan, September 20 – 24, 2009. http://richard.hofer.com/pdf/iepc-2009-138.pdf
   Szabo, J., Robin, M., Paintal, Pote, B., S., Hruby, V., “High Density
   Hall Thruster Propellant Investigations,” 48th AIAA/ASME/SAE/ASEE
   Joint Propulsion Conference, AIAA Paper 2012-3853, July 2012.
   http://arc.aiaa.org/doi/pdf/10.2514/6.2012-3853
   • Marcel Williams says:

     April 20, 2015 at 9:08 pm

     Using xenon, of course, would mean utilizing an interplanetary architecture that is dependent on an expensive– terrestrial fuel. But even if you use xenon, you’re not likely to launch astronauts aboard such a vessel directly from LEO since it would take too long to travel through the Earth’s radiation belt. So crewed interplanetary journeys will probably begin at one of the Earth-Moon Lagrange points.

     And you’re still going to need a substantial amount of water (probably over 150 tonnes) for drinking, eating, washing, the production of air, and for radiation mass shielding. Supplying that water from the Moon’s low gravity well would be a lot cheaper than supplying that from the Earth– especially if the vehicle is used again for future crewed missions.

     Marcel
     • billgamesh says:

       April 22, 2015 at 12:22 am

       “So crewed interplanetary journeys will probably begin at one of the Earth-Moon Lagrange points.”

       My thinking on bomb propulsion concerning this has evolved over the last five years or so from the firm belief that only a metal disk massing several thousand tons will work to the reality that a “soft” interim will be necessary. I imagine this craft would begin it’s journey from a lunar “frozen” polar orbit after filling up it’s radiation shield with water.

       The Medusa concept, which uses a several thousand foot diameter parachute and utilizes kilometer long spooled cables to reduce acceleration, is the most likely candidate for a interplanetary spacecraft that could be available in the next quarter century. There is also the option of lifting a metal plate up a slice at a time and welding it together in space. I am guessing the “slice at a time” would require a much larger launch vehicle than SLS. Perhaps both methods will be used while developing the lunar manufacturing capability to produce the really huge plates necessary for efficient pulse propulsion.

       I also doubt the first true spaceship mission outbound would be going to Mars. Ceres is a better destination. It can land and utilize the ice and explore the possible ocean with mini-subs.
5. Marcel Williams says:

   April 20, 2015 at 4:23 pm

   “The Moon contains what we need to create new capabilities in space faring and is critical to achieving Mars and all of the other interesting destinations in the Solar System.”

   Very well said Dr. Spudis! And a great article in general.

   My preference for using liquid hydrogen over liquid methane for reusable propellant depots, interplanetary rockets, and reusable shuttles are as follows:

   1. Hydrogen and oxygen propellant can almost indefinitely be stored as water at orbiting propellant depots. When LOX and LH2 are needed to fuel an interplanetary journey, the propellant can be produced through solar or nuclear powered electrolysis and cryocooling just a few weeks or months ahead of time.

   2. Solar powered cryocoolers can also be used to re-liquify ullage gasses on LOX/LH2 interplanetary orbital transfer vehicles for zero boil-off of hydrogen and oxygen.

   3. Propellant manufacturing– water depots– can also provide the habit modules of interplanetary vehicles with water for drinking, washing, oxygen production and for mass shielding the habitat from deleterious levels of cosmic radiation and major solar events.

   While liquid methane has the advantages of smaller tank volume and reduced boil-off relative to liquid hydrogen– it also has the disadvantages– of having a much lower specific impulse plus the need for an additional (none methane) ignition source of fuel in order to start the engine.

   Even on the surface of Mars, it would be simpler to manufacture and fuel a shuttle vehicle with LOX/LH2 from martian sources of water rather than trying to produce methane and oxygen from CO2 and martian water– plus the ignition fuel.

   A methane depot program would still require the deployment of a water depot– possibly even for the production of oxygen. But a propellant (LOX/LH2) manufacturing water depot, on the other hand, would only be one simple solar or nuclear powered machine that could do it all!

   Marcel
6. billgamesh says:

   April 21, 2015 at 9:55 pm

   And now the inconvenient truth nobody wants to hear: chemical propulsion is essentially useless for interplanetary travel. It is non-negotiable that human missions BELO (Beyond Earth and Lunar Orbit) will require nuclear energy.

   Because it is a politically incorrect subject nobody will touch it- so the only thing left to discuss is manufacturing rocket propellent from lunar resources. It is a confusing and ultimately self-defeating situation. It seems even more hopeless when a further extremely unpopular fact comes to light: there is only one form of nuclear propulsion that will work- bombs. Go ahead and eye-roll, I know you cannot help it. But as someone once said, “the universe is not only queerer than we suppose….”

   It is not that manufacturing this propellent is pointless; it is only pointless for travel beyond cislunar space. For operations involving transits from GEO to the Moon and back it is of course the only way to create any infrastructure. But since Mars is the present public relations hook, the “horizon goal”, lunar resources must be talked about in a Mars context. Since a cislunar infrastructure would be required to build the atomic spaceships capable of interplanetary travel then it is not exactly a deception- more of a facade.

   Square one is radiation. It is why the Human in Human Space Flight comes first. Slowly but surely it is being admitted that massive shielding is required for long duration missions. Dragging space advocates kicking and screaming to this door still does not mean they will open it. The NewSpace philosophy is directly opposed to what such massive shielding entails- equally massive state-run projects. But it is unavoidable and makes the previously stated inconvenient nuclear truth unavoidable. Only nuclear energy can push a cosmic ray water shield massing in the neighborhood of a thousand tons around the solar system. This is a conservative figure considering it takes 500 tons to shield a small capsule. For multi-year missions a great deal more space will be needed to prevent psychotic astronauts.

   Space radiation and the consequential requirement for nuclear propulsion inescapably takes us to the Moon. The Moon is no distraction, it is the prerequisite. A thousand tons of tap water is not going to be lifted out of the gravity well of Earth. Nuclear devices are not going to be tested anywhere in the magnetosphere.

   But nobody is saying a word about any of this in the media. They would be crucified.
   • billgamesh says:

     April 21, 2015 at 10:07 pm

     I would add the money to enable lunar based atomic spaceships has to come from somewhere besides emoting space cadets writing letters to their representatives.

     Presently there is only one revenue producing space industry: satellites. In my view the only construct sharing all the available technology and resources is that classic icon of the 50’s, the von Braun wheel. Assembling wheels in lunar orbit out of wet workshops and filling them with water lifted from polar ice deposits, then transiting them back to GEO, is my solution. I am a troubleshooter by trade and the flow chart says this is the only fix.

     The 100 billion dollar plus yearly revenues from the satellite industry can be captured by replacing the present GEO junkyard with far more efficient and capable human crewed space stations. But nobody is saying a word about this either.
   • Marcel Williams says:

     April 22, 2015 at 12:15 pm

     Parker’s 500 tonne estimate is based on a capsule surrounded by water– five meters deep. The would reduce radiation levels during solar minimum conditions below 5 Rem per year. 5 Rem per year, of course, is the maximum level of radiation exposure legally allowed for radiation workers on Earth. NASA, however, has a maximum radiation exposure limit of 50 Rem per year for astronauts and a 100 Rem lifetime exposure limit for the most vulnerable astronauts (females approximately 25 years of age).

     But I would add an additional rule that would limit exposure during an entire round trip mission to less than 50 Rem so that a young female astronaut could make an additional deep space voyage during her career. One trip to Mars is like limiting Columbus to one trip to the Americas– even though he thought he was in South Asia:-)

     30 centimeters of water should be enough to protect astronauts from heavy nuclei and major solar events during an interplanetary journey while also exposing them to less than 25 Rem per year of cosmic radiation. This is about 20 centimeters less than what I usually advocate. But 18 months (9 months to Mars and 9 months back) through interplanetary space with a 30 centimeter water shield would still only expose astronauts to about 38 Rem during solar minimum conditions (the worse conditions).

     Since astronauts would probably reside in regolith shielded habitats on the martian surface that would probably expose them to less than 5 Rem per year during solar minimum conditions, less than 10 Rem of additional radiation exposure would be added to the mission. But that would still expose astronauts to less than 50 Rem in total during the entire mission. Working and exploring on the martian surface for a few hours every week would only add a couple of Rem exposure during the mission.

     Marcel
     • DougSpace says:

       April 22, 2015 at 2:49 pm

       Marcel, If you are open to giving the astronauts on the Martian surface a “radiation budget” then perhaps we could also have a budget for them during transit. Most of anyone’s time is sedentary such as sleeping, working at a desk, or reading this post. In this case, they could be in a small area with just enough elbow room to be comfortable. But they are given a certain amount of time each day to head out to a relatively unshielded inflatable habitat to stretch their legs. The 50 cm of hydrogen-bearing shielding could be the provisions and propellant that they would need to be taking along anyhow.
       • Marcel Williams says:

         April 22, 2015 at 8:07 pm

         Thanks for you interesting comments Doug!

         With a practically infinite amount of regolith lying around on the martian surface, it should be pretty easy to shield habitats deployed on Mars to Earth radiation standards.

         For interplanetary journeys, however, I would dump the water shields for the twin artificial gravity habitats before the final trajectory burns into orbit, which would substantially lower fuel requirements.

         Once in high Mars orbit, a pre-deployed propellant producing water depot (filled with water originating from the Moon) would supply the interplanetary vehicle with both water shielding and LOX/LH2 for the return trip to cis-lunar space. Eventually, the martian moons could be the source of water for return trips to cis-lunar space.

         For interplanetary missions requiring several months aboard ship, I think it would be essential for the psychological health of the crew for the habitat modules to be reasonably comfortable and spacious. That’s why I propose using the– uber lite– habitats derived from SLS propellant tank technology.

         SLS Fuel Tank Derived Artificial Gravity Habitats, Interplanetary Vehicles, & Fuel Depots

         http://newpapyrusmagazine.blogspot.com/2014/05/sls-fuel-tank-derived-artificial.html

         Utilizing Lunar Water Resources for Human Voyages to Mars

         http://newpapyrusmagazine.blogspot.com/2015/01/utilizing-lunar-water-resources-for.html
     • billgamesh says:

       April 22, 2015 at 6:32 pm

       “-5 Rem per year, of course, is the maximum level of radiation exposure legally allowed for radiation workers on Earth. NASA, however, has a maximum radiation exposure limit of 50 Rem per year for astronauts and a 100 Rem lifetime exposure limit-”

       What you don’t understand is that young females will be at greater risk than middle age males no matter how much you play with “adjusting” their exposure. There is a reason for that “legal” exposure limit. Playing the exposure game is a dead end. It is ethically flawed that astronauts have to volunteer for missions that permanently damage their health and will kill a certain percentage of them with cancer. You have to realize this is a part of Human Space Flight that is not adjustable. Standards for workers on Earth are not based on an adjustable death rate for certain occupations. Legally and ethically there is no solution except providing a base line Earth environment. Astronauts are radiation workers. NASA, by setting exposure limits so far above what is allowed on Earth, is setting up Human Space Flight for failure. It is bad enough that leaving Earth orbit means an unavoidable radiation bath going through the Van Allen belts. The rest IS avoidable and trading off lifespan for less expensive spacecraft is THE showstopper.

       If human beings are going to go into space for years at a time the “Parker minimum” is the reality and “adjusting exposure” is the showstopper. It is happening- objections to exposing astronauts to these health hazards without providing them lifetime medical care and several flat pronouncements that radiation makes deep space missions impossible.

       Near sea-level radiation and Earth gravity, the “Parker minimum” is the prerequisite that will enable enable long duration human space flight beyond low Earth orbit. Failing to provide this minimum environment means no human space flight. There is no cheap.

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