Lunar Millenium A low-cost manned moon mission architecture Revision 5.21 George William Herbert Retro Aerospace Technical Report RA-96-1-21 Feb 19, 1996 0. Introduction Lunar Millenium is a program intended to provide nearterm, low cost manned lunar mission capability. It assumes no major technology developments and existing launch vehicles. LM Rev 5 is intended as a mission architecture to meet the "Goldin Challenge" of a manned return mission to the Moon for $1 billion or less, yet allowing easy transition into an ongoing exploration program for deeper exploration and development of the Moon. 1. Overview The Lunar Millenium Initial Program (LMIP) provides for two manned expeditions to the moon. The first is a minimal mission using just one manned lander and one astronaut, who will do little more on the surface than the Apollo 11 crew accomplished. The second mission is to have serious science objectives. Two one-man and one unmanned vehicle launched on Titan or Proton class (15-20 ton to LEO) launch vehicles. All vehicles use a standard new Centaur stage with a single RL-10 engine able to provide transfer and lunar descent propulsion. Actual landing is accomplished (from a staging height of about 50m) by the LM ascent stage. The unmanned support craft are launched first to the exploration site, then the two manned vehicles are flown within a short interval to provide a nominal 10 day stay time for the two astronauts. The two astronauts return in the same capsules the arrive in. The LMIP is intended to be a pathfinder mission for an ongoing program of lunar exploration, rather than merely a minimalist flags and footprints return. Nearly all the hardware needed for the Lunar Millenium Extended Mission is developed in the initial program (indeed, is required for the initial program). Minimal followon work to develop the extended stay base facilities required for semipermanent exploration stays will build upon the Lunar Lander Centaur, the existing LM Capsule and the minibase and rover unit flown as the unmanned support mission in the initial program phase. Retro Aerospace considers this followon capability a moral necessity for a reasonable mission architecture, though obviously budget and political constraints will determine if and how it is used. The Extended Mission is described but not required for the Inital Program. 2. Hardware 2.1 Lunar Lander Centaur Based on the uprated, single engine Centaur now in development, the Lunar Lander Centaur (LLC) is the optimal solution for orbital transfer and landing propulsion requirements. The high efficiency RL-10 motor is flight proven dating back to the origional Apollo program. The only potential hardware modification to the single- engine Centaur will be the possible use of the RL-10A5 current generation engine should the uprated RL-10 in development for the single engine Centaur prove unable to throttle low enough for reasonable descent profiles. Software modifications for the base-first landing profile during descent on the moon will be required, or external guidance inputs, but the hardware should be unmodified excepting the potential engine selection. Payload to descent handoff (50m altitude, 5 m/s Z nominal) is roughly 3000 kg. Further modeling of the descent should solidify the payload number, but until that is complete an assumed payload of 2500kg is the design specification for the other mission components, giving a margin of 20% for the landed payload mass at this time. 2.2 Lunar Millenium Return Capsule and Auxiliary Module The Lunar Millenium Capsule (LMRC) is a 500 kg loaded class light manned capsule. Earlier work has shown that 350-400 kg class minimal manned capsules are viable from an engineering standpoint. 500 kg is specified at this stage to allow for additional growth and margins. The capsule is a 2m diameter, 1.5m tall truncated cone which re-enters base first as with previous manned capsules. There is a single seat and minimal additional space for movement by the astronaut. Mated to the Return Capsule proper during the flight to the moon and throughout surface operations is an additional module, the Auxiliary Module. The AM is a cylinder roughly 2.5 meters tall and 1.6 meters in diameter, giving work space for the astronaut to enter his lunar surface suit as well as habitability space during the earth to moon transfer. The AM masses about 200 kg including fittings, and additionally carries the 100 kg lunar surface space suit. During the transfer segments the astronaut will wear a lighter 30 kg pressure suit. The surface operations suit and the AM are jettisoned prior to the ascent from the lunar surface and return to earth. 2.3 Ascent Vehicle The Ascent Vehicle is a single stage vehicle which provides the final lunar landing propulsion as well as all the propulsion capability to return the LMC to earth from the moon. The Ascent Vehicle also provides return-to-earth abort capability should the Lunar Lander Centaur fail at any point in the mission. The normal handoff from LLC to ascent vehicle on landing is at 50 m height on descent, at a descent rate of 5 m/s. The Delta-V budget for this stage includes: 106 m/s for landing and hover, 2,800 m/s for earth return injection, and 94 m/s reserve (total of 3,000 m/s). The landing and reserve delta-V capability includes the capsule and the auxiliary module; the return delta-V only assumes the capsule (and astronaut) as payload, assuming the auxiliary module is jettisoned prior to liftoff. Total wet mass for the Ascent Vehicle is 1700 kg; 1440 kg propellant and 260 kg stage mass (18%). Nominal payload to return trajectory is 500 kg, the fully loaded mass of the return capsule including the astronaut. 2.4 Support Module The Support Module is the main unit landed at the exploration site ahead of the arrival of the two manned capsules. It is a minimal pressurized module intended to provide sufficiently habitable space to keep the astronauts functioning efficiently during the surface stay. This includes low-G toilet, suitably comfortable sleeping spaces (Apollo demonstrated hammocks insufficient), food supply, etc. As descent handoff from the lander Centaur occurrs at some altitude above the lunar surface, the Support Module requires a minimal onboard propulsion system. This consists of two parts; a set of liquid rocket motors providing thrust to offset lunar gravity but not slow the descent, and a cluster of solid rocket motors to slow the descent. 25 kg of fuel is budgeted for the liquid motors, with 10 kg of motors and tankage and piping. 8 solid motors with enough impulse to slow the unit about 1.5 m/s each, with 1.5 kg of propellant and 1.0 kg of casing and nozzle, are provided. A small doppler radar unit will fire enough to provide a minimal impact landing, the rest being left for later use or abandoned. The Support Module has an additional emergency role. Should the Ascent Vehicle or Capsule fail for one of the two astronauts, it provides a shelter with at least 20 days additional life support capacity beyond the specified endurance, including overnight capability. This capacity will allow the launch of a rescue capsule (standard capsule stack, but unmanned) to autoland at the base and allow the astronaut to return safely to earth. The 20 day requirement is estimated from vehicle and launch vehicle prep requirements, and should be detailed further during mission development and definition. The Support Module masses about 2050 kg, including systems and stores. 2.5 Rover Two mini-rovers are included with each Support Module unit. These are nominally the same vehicle type as the Apollo rover, with the following likely improvements: better batteries for longer distance missions, rearranged primarily for single driver use (though fully capable of carrying two riders as the origional), improved inertial navigation system, potentially further development. The Apollo rovers massed about 210 kg each. It is assumed that EVA missions with both rovers operational will be limited only by life support endurance. If one fails, the other can carry both astronauts back to the base. Should one fail, further exploration with the remaining rover is safe within EVA walkback distance from the base, which is limiting but not a total loss of science mission. 2.6 Base Modules (Lunar Millenium Extended Program) These modules are intended to provide longer term (months) habitation and work space for followon missions. This includes nominal rather than emergency-only overnight stay capability. Further definition of the Base Module units will proceed as the Extended Mission is further defined. One major change which is predicted is that the Base Module units will have to be buried under regolith or in lava tubes for meteoriod and radiation shielding, as they will be inhabited for considerably longer than the short term support modules. 3.0 Operational Issues 3.1 Test / Operations Plan The following development steps are assumed for the program: 0. ground development of one prototype unit of all vehicles 1. unmanned flight+reentry test of capsule on LLV/Conegesta/Taurus "K- mission" 2. manned flight test of capsule, auxiliary module, ascent stage on Delta "K+ mission" 3. manned flight test of LL Centaur, aux mod, capsule, ascent stage to lunar orbit but not landing "L mission" 4. landing with one person "M mission" 5. full mission, 2 astronauts and 1 unmanned base unit "N mission" 3.2 Extra set of flight hardware considered essential A backup manned capsule stack is required as an emergency option in case of failure of capsule or ascent stage of one vehicle on the second expedition. 3.3 Operations Activities The operations budget covers the flight operations necessary to perform the two expeditions. An operations staff of 50 full time personel for a period of 4 years (planning through second expedition) is assumed, with an additional 100 engineers from the development programs retained in the operations department. This budget also includes some costs of the astronaut program directly related to the LMIP mission, specifically training 6 astronauts (first expedition, second expedition, and backup) for the mission and their support costs during training. The astronaut training may exceed this budget item, hopefully some in kind support from the astronaut office will reduce the amount charged to the LMIP project in this area. 3.4 Schedule The development and testing phase of the Initial Program is expected to take about 42 months total. The first lunar mission would be at roughly 48 months into the program (no landing), the second at roughly 54 months (first 1 man landing), and the third at 60 months (full 2 man landing with base module, full exploration mission). The Extended Program could follow immediately thereafter if funding is available at that time. A more detailed schedule is being developed in a seperate document. 4.0 Lunar Millenium Initial Program Costs Per the "Goldin Challenge" to produce a viable mission architecture within a project budget of $1 billion, that is the Lunar Millenium Initial Program's specified maximum budget. Further budget details are available in the seperate budget report. (the budget has been seperated, along with detail plans, as they are rapidly evolving while the overall architecture is stable within Revision 5). 5.0 Lunar Millenium Extended Program Three scenarios for ongoing missions beyond the initial program are detailed in the budget document. The aggressive scenario forsees 2 missions (2 astronauts, 2 advanced base units each) per year on an ongoing basis, for a cost of about $800m per year. The low-rate scenario forsees 1 mission per year on an ongoing basis, with a budget of about $500m per year. The minimal extended program would fly 1 mission every 2 years, for about $250m per year. These funding levels are largely (abt. 50%) made up of launch costs and are unlikely to be able to be reduced further. No extended mission is required in the initial program mission plans, but should an extended program be approved it should happen at least 2 years before the end of the initial program to allow the contractors to keep their production lines and staffs open and available. 6.0 Comments The Lunar Millenium program is a bold and aggressive challenge to the status quo of manned missions. It is risky, and pushing the envelope. But it is feasible, and sufficient margins and fallbacks are available for reasonable astronaut survival chances. We believe that this represents a viable solution to the problem of returning to the Moon.