| Conquering the Moon with Delta 4 Rockets: A Cursory Analysis David A. Dietzler, 2007 The High Frontier Revisited In 1976 Gerard K. O'Neill and others created The High Frontier and the prospect of space colonization to generate energy for Earth with solar power satellites. The original plan involved spending about $250 billion over ten years to place 3000 to 20,000 tons on the lunar surface with Shuttle derived heavy launchers that could place 80 or more tons in LEO. Today, such rockets do not exist, but the job can still be done. Imagine 100 Delta 4 heavy launches and 2500 tons of payload to LEO at 185 km. Perhaps they could be launched from Koru, French Guiana to achieve a somewhat higher orbit that will not decay as fast that also has a more favorable orbital plane for launch from LEO to the Moon. If we have NEP tugs with 10,000 second drives and vapor core+MHD power plants that generate at least 1 kWe/kg. that amass 20 tons we find that only 1.9 tons of propellant is needed to get to low lunar orbit with a 25 ton payload. Exhaust velocity of ion tugs = 10,000*0.0098=98 kps Since about 4 kps needed for Earth escape and braking into LLO, mass ratio = e(4/98) =1.04166 Propellant mass = 1.04166*45=46.8747 46.8747-45»1.9 tons Since the tugs have to return to LEO we must factor in the reaction mass for this. 1.04166*20=20.8332»20.85 850 kg. of reaction mass for return to LEO. Less would be needed if aero braking is used. Since this increases the Moon bound mass we find: (25+20.85)*1.04166=47.76 A total of roughly 2.75 tons of reaction mass is needed per roundtrip. A total of 275 tons of reaction mass is needed. If robotic ice miners and landers that use NTR and water in Kevlar bags for a high mass ratio are used no fuel for landers must be up-ported to the Moon. The O'Neill team did not know of this water resource on the Moon, although they suspected it. There is some controversy regarding the ice, but let's be optimistic. The ice miners might amass two tons each like a large automobile and the landers no more than 20 tons each. If we use five miners capable of pumping their water loads into the landers and two landers we have a total of 50 tons. To land this with NTR using water for reaction mass and an Isp of 400 seconds: NTR exhaust velocity = 400*0.0098= 3.92 kps Since 1.6 kps is needed to land from LLO, mass ratio = e(1.6/3.92) = 1.5 Propellant mass = 50*1.5=75 thus 25 tons of reaction mass needed This must be sent to LEO and then by ion tug to lunar orbit. Water will not boil off during the multi-month voyage. Five ice miners + two landers + landing propellant = 75 tons. About nine tons of ion propellant brings us up to 84 tons. We might need some teleoperated orbital devices for transferring propellant and assembling the payloads, so let's estimate 125 tons for this ice mining 'bots and "nuclear steam" landers system to LEO. We could land 2000 tons of industrial payload on the Moon, cannibalize cargo modules and Delta 4 upper stages, and even land the tugs to convert them to power plants on the lunar surface. 2500 (100 Delta 4 payloads to LEO) - 100(five tugs) -275(ion propellant) = 2125 tons payload lunar 2125 -125 (miners+landers, etc.) = 2000 tons to lunar surface The Costs At $170 million (1999 dollars) per Delta 4 launch this would cost $17 billion. A drop in the bucket. The payload would consist largely of power supplies, stereo lithographic machines and metal extraction devices. This payload would multiply its own mass many, many times over as the years tick by. To get humans to the Moon we would use something like the Artemis Project system. Human crews would be minimal at first and robots will be primary. Since the tugs could be landed on the Moon and converted to power plants we get another 100 tons although it may be argued that the tugs could be left in space for future cargo hauling. Occasional refueling with uranium or thorium will be required. The 50 tons of mining 'bots and landers should also be considered to be lunar cargo, so we've actually got 2050 tons to the Moon and some space transit infrastructure in the form of the NEP tugs. Also, we would get 100 Delta 4 upper stages amassing 3.5 metric tons each for a total of 350 tons of metal ready to be worked into various parts. These upper stages are 5m(16') wide and 12m(40') long. They would make excellent orbital fuel depot storage tanks for fueling up high thrust manned ships and habitat modules on the lunar surface. 2050 +100 (tugs)+350 (upper stages)=2500 tons of useful cargo ( ignoring those teleoperated devices for transferring propellant to landers). That works out to about $3400 per pound. Not counting the tugs and upper stages, about $4150 per pound. Astrodynamics Wizards Wanted The Mark Maxwell ice tanker consists of a Kevlar bladder filled with water and a NTR engine. It would operate in conjunction with robotic ice miners to land payloads on the Moon that were lofted to LEO by Delta 4 rockets and transported too LLO by NEP tugs. It could also move water to L1 where it is loaded in aero braking modules and shot down to LEO depots when we have a station at L1 capable of splitting water into hydrogen and oxygen. This would be faster than using ion drives and time is often money. It only takes 3150 m/s to go from LEO to L1. Locating a station at L1 should be more efficient than going from LEO to LLO. A minimum energy ellipse from L1 to the lunar surface and vice versa requires a delta V of about 2.3 kps and 70 hours. This would put payloads on the far side of the Moon. If we send payloads from L1 to LLO and then retro down from LLO to the near side surface about the same amount of energy is required. We could also travel directly to the near side from L1 in an almost straight line but this will require more energy. Since the Mark Maxwell ice tanker may have a very high mass ratio and 400 seconds or more specific impulse it might do the job. This gives mission designers and mathematicians plenty to think about if they are looking for something to work on! Those who are knowledgable might also point out that I have treated maneuvers with ion drives as if they were impulsive delta Vs and the actual astrodynamics are more complex. Perhaps twice as much propellant for ion drives or about 550 tons will be needed! I'm not asking anybody to clean up my mess, I'm just trying to spur some thought out there! I don't have the mathematical prowess or computer programs to make low thrust long duration trajectory calculations but one can estimate that twice as much delta V is needed as an impulsive thrust delta V and that roughly doubles propellant mass requirements with the mass ratios we are looking at here. Then and Now Many technologies exist today that did not exist in 1976. Computers and robotics have exceeded the expectations of the most optimistic speculators and they will continue their relentless progress so that by the time we actually commit to a space colonization program we will have some really capable AI robots for work in space. By using AI robots we could avoid the expense of building Bernal Spheres for 10,000 people. T.A.Heppenheimer thought that magazines would be faxed to high orbit and Xerox copies would be distributed amongst space colonists. He didn't foresee the internet, laptops, PDAs or DVD players, at least not publicly! In 1976 that was science fiction! The relatively simple FFC process for extracting titanium for titanium dioxide did not exist back then and the early NASA studies looked at the laborious Kroll process for refining titanium in space. The Delta 4, Atlas 5 and Titan 4 did not exist almost thirty years ago and everyone expected reusable Shuttles to be cheaper than evolved expendable rockets like the previous three mentioned. The vapor core reactor with MHD which can get 1 kWe per kg. of system mass or better like that which is being developed at the University of Florida's Innovative Nuclear Space Power Institute did not exist either. In the seventies the best space nuclear power systems could get about 100 kWe from four tons of mass or about 1kWe per 40 kg. with almost 20 times as much power wasted as reject heat! More technological breakthroughs are certain to come in time for a space colonization, industrialization and energy program. We might even see the use of artificial spider silk from GMOs which has five times the tensile strength of steel and C60 nanofiber based materials as well as AI computers with nanocircuitry. We might make use of gallium-indium-nitride solar panels that are 70% efficient and high temperature 77° K superconductors. Stereo lithography and laser additive manufacturing are far more advanced today and it will be possible to make molds from basalt for casting aluminum and magnesium as well as make parts directly from powdered titanium. In the free vacuum it should be easy to make powdered metals by evaporation of molten metals. We will not ship mass drivers up to the Moon in finished parts. We will build them from local resources. The equipment sent to the Moon will consist mostly of power supplies, regolith refining devices like magma electrolysis furnaces, fluidized beds that use hydrogen to reduce ilmenite, magnetic separators, centrifugal grinders that need no abrasive wheels or grit that wears down with heavy use, Sabatier reactors and related gear to recycle carbon from CO gas formed during smelting, sulfuric acid makers, robotic mining shovels, stereo lithographic and laser additive manufacturing devices. Integrated modules might receive moon dust on one end while iron, titanium and ceramics come out the other end. Other modules will have inputs of metals and parts as output. We will make everything we can on the Moon from aluminum mass driver coils and titanium bracings, ceramic bricks for smelting furnaces, LOX tanks, molds and glass-glass composite materials to vehicles and volatiles/helium three mining machines. Smart robots with teleoperated assistance from Earth and small crews on the Moon will assemble everything. We will even make habitat modules from local resources of iron and titanium. We will ship seeds to the Moon and grow crops in lunar soil fertilized with N, P and K mined on the Moon to create a food supply for future crews. The original 2000 tons of machinery will create more machinery and grow into a multi-million ton industrial base on the Moon like a tiny seed growing to become a mighty oak tree. This will take a lot of ingenuity, sophisticated software and human brainpower, but I am confident. |
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| Justifying the Cost Spending $17 billion to launch 100 Delta 4 rockets is not exorbitant. That's about the cost of eight new nuclear power plants. The actual cost of the program will be much higher when we include the cost of developing all the robots, ion tugs and ground support and operations centers. Operations centers will be located around the world and linked by cable and satellites. Sophisticated software will be needed to make everything work. We will also need remote control technicians to drive the robots on the Moon and operate the mining shovels. The young generation of video game enthusiasts will provide plenty of human talent for this. Global ground control centers will make it possible for daytime crews on Earth to operate the lunar machines 24 hours a day without forcing anyone to work the graveyard shift. The total cost of the program will be several hundred billion dollars with launch costs being a minor fraction, even at $3400 to $4150 a pound! The cost is justified because the benefits will be clean solar energy from space and helium 3 fusion fuel with tourism and astronomical observatories coming later as icing on the cake. Let's consider the price of nuclear fission. Today it costs about $2 billion to build a nuclear power plant generating 1000 to 1500 MWe. In 2050 based on projected rates of growth we will need 53 TW of power. Even at this level of production half the world's people will have about as much energy as Mexicans do today and the other half about as much as Europeans. To generate 53 TW with fission we'd need about 50,000 power plants rated at 1 GWe each and this would cost $100 trillion! Even if we get about 20% of our power from winds, biomass, some fossil fuels, hydro and other sources we will still need 40,000 nuclear power plants. If the efficiency of these plants is increased by co-generation (also called combined heat and power) from a typical 35% to 70% we will need 20,000 nukes at a price in today's dollars of $40 trillion! Add the costs of waste reprocessing, waste disposal, increased global security costs to prevent nuclear proliferation and nuclear terrorism, and accidents to the picture and nuclear power becomes a costly way to defeat global warming and provide energy to the world. Space solar power will be much less expensive once we are tapping resources from the Moon instead of launching them from Earth. The program could be an international government-private corporate partnership. Preferably, the government role would be minimal or the project will become another pork barrel that politicians use to create jobs for their constituents and business for their corporate supporters. Perhaps government should limit its role to tax credits, awards, subsidies and defense contracts. Finally, it is apparent that nuclear fission is the only non-carbon emitting energy source today that can be used for large scale reliable power generation, but the cost is outrageous even compared to space travel. For a few hundred billion dollars we can industrialize the Moon, build some powersats and start selling electricity. Reinvestment of profits will pay for the construction of more powersats and the initial investment will grow. Stocks sold to finance the project will increase in value. The economics of space solar power are far superior to nuclear power, despite the cost of rocket launches which tends to scare people off. The hostility of the space environment is no great threat to robots. Putting humans in space is a challenge but we've learned how to do this with years of experience on the Russian Mir and now the ISS. Supplying humans in LEO, GEO and on the Moon will be far easier than keeping humans alive during three year missions to Mars. We might even develop LUNOX augmented nuclear thermal rockets that can reach the Moon in 24 hours. These could be launched atop Delta 4s which have a five meter diameter payload capacity or made from converted Delta upper stages. Some nuclear power will be needed in space but the risks presented by this will be miniscule compared to 20,000 nuclear power plants on Earth. Unimaginative corporate and political leaders might scoff at space power and advocate nuclear fission. That could be the greatest obstacle to the development of the High Frontier. |
| see: http://www.neofuel.com/space98/ Concept by Anthony Zuppero Painting by Mark Maxwell |