The longer answer is that the EIA is very, very conservative.
At lunar takeoff, this tanker would mass tons, but since it is taking off in lunar gravity, it would effectively weigh only about 62 tons. The composite propellant tanks, similar to what will be used for the BFR, would probably mass only 20 tons, leaving 2 tons for the engines, 2 tons for the landing legs, and 6 tons for the rest of the structure, including the cryo-coolers, sunshade and power system.
This provides a structural mass fraction of 8. At this point, we do not know the actual cost of the lunar propellants as delivered to the tanker at the lunar base, including the vehicle development costs, but finally we can compare the relative mass of the delivery propellants.
Assuming that we have not underestimated the tanker mass, the delivery propellant mass from Earth to LEO to L1 is Note that this mass difference is about three to four times larger than the typical cost difference of 15— Cost of lunar fuel would include fuel production costs, transport propellant costs, and vehicle operation costs.
Even the cislunar tanker must undergo an aerocapture to return to LEO from L1, while the lunar-to-L1 tanker would encounter only the stresses of thrust and landings.
In addition, propellant at L1 is at least twice as valuable as propellant in LEO, due to the gravitational potential and additional velocity from an Oberth maneuver performed starting at L1. If future lunar entrepreneurs can beat that price, and if lunar water ice does exist in minable quantities, the lunar fuel production enterprise seems assured.
Sales of large amounts of propellant for Mars expeditions would assure a robust human presence on the Moon. However, to assure that the logistics capability of any cislunar or L1 base will exist, the propellant depot and cargo handling capabilities must be a part of the design of the base from the beginning.
Plans for the NASA cislunar base must accept that large propellant depots can be attached to it. We are getting significant indications of international interest in a lunar base. Why does the cislunar base have to be so small if there is support for it?
The solution to this problem is a package deal agreement where there is a combined cislunar, lunar, and fully reusable transport development effort taking place simultaneously, with the international partners providing some of the transport and lunar surface infrastructure, with heavy reliance on commercial launches.
Development would take place so that the first human landings at a lunar base site would take place within a year of the cislunar base completion.
The first and most obvious customer is NASA; an orbital fuel depot would allow them to launch satellites on smaller LVs or launch larger satellites, allowing a choice between savings on the LV and increased capabilities on the spacecraft. Perhaps less obvious, Russia would see a significant benefit from a LEO depot in the plane of the Baikonur launch site.
Vehicles would refuel in order to plane-change to an equatorial orbit for GEO deployment. Further into the future a fuel depot would be essential for the smooth operation of tugs and satellite tenders, serving as a buffer between fuel launches and fuel used in missions. I think the current leader is Boeing with their in-development ACES vehicle using integrated fluids management.
Hypergolic fuels require a different set of technologies and would most likely require shipping expendable supplies of a pressurant, either nitrogen or helium, but they have a larger potential market right now as hypergolics are typically used for satellite stationkeeping and orbit changes.
The third fuel category is inert gases argon, xenon for ion engines; these can be stored as compressed gases or cryogenic liquids.
I think a near-term possibility is simply to ship water. It is dense, relatively inert and can be used as a life support consumable or as a propellant after electrolysis. It has a high surface tension and can be wicked out of a bulk tank in microgravity without pressurants or membranes. There are cubesat-scale thrusters available today that separate water over time, accumulating a charge of gaseous O2 and H2 using small amounts of power, then ignite that fuel in a high-efficiency engine.The 9 Steps to Financial Freedom: Practical and Spritual Steps So You Can Stop Worrying [Suze Orman] on iridis-photo-restoration.com *FREE* shipping on qualifying offers.
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