Monday, April 15, 2013

Commercial Moon Missions Imagined

Apollo took men to the Moon. Many unmanned craft of Russia and US and now other countries have made it to the moon. Soon to follow are commercial companies. Now, China wants to send Taikonauts to the moon. I don't blame them since a progressive space program can produce lots of research that helps their economy.  How would commercial companies go to the moon?  What vehicles would they need?  How should they differ from past manned missions?  Learning from Apollo, it's obvious that certain modules are needed to make any mission to the moon work.  You need a capsule to return the crew to Earth, you need an in space booster, or two, to get the crew and equipment from earth to the moon and back, and you need a lander.  Now, if your not going to the surface, you will need a space station made up of at least one module. It goes without saying that you need to supply all the fuel and other consumables for those vehicles.  Let's look at how these modules might be for a cool commercial effort that comprises of many missions to our natural satellite.

Why a capsule?  Well, let's put it this way, two superpowers chose the capsule to return crew from the moon. Even though Soviet Russia did not do a manned mission to the moon, they did plan for one. Capsules are concise and able space vehicles. I've heard space professionals say that wings are not needed in space. A space plane would have extra weight, and weight is the Achilles' heal of flight. When your traveling a half a million miles round trip in space, wings seem like a luxury.  So capsules it is.  What's great right now is that SpaceX is pushing the development of the capsules to have them set down on land with a propulsive landing and be able to be reused for more missions.  That is a far cry form Apollo days which relied extensively on a service module for crew survivability over the length of the mission.  SpaceX Dragon only has solar panels that are not incorporated into the capsule itself.  Everything else is.  Now, a capsule needs a beefier heat shield for lunar missions than just Earth orbit.  The temperature difference is about 2000 degrees Fahrenheit (1093 degrees Celsius) between reentering Earth's atmosphere from low orbit and from the Moon.  Currently, it is only feasible to have the capsule reenter the Earth atmosphere coming from the moon rather than trying to enter an Earth orbit.  We have not figured out how to go from Moon orbit to Earth orbit with a manned mission yet.  Though, in the future that could be a preferred way of doing business.

ESA'a Smart-1 ion drive to Moon
Trans Lunar Injection (TLI) was the maneuver used to take Apollo from Earth orbit to lunar orbit.  They used the upper stage of the Saturn V rocket to perform it and then jettisoned the booster.  Yes, I did not mention the Command Module docking with the Lunar Module because it's not relevant right now.  That may have worked for NASA but commercial efforts would require re-usability for many missions over time.  So to take care of the TLI function a reusable tug is in order.  Now this tug has to accommodate both manned an unmanned missions.  So, two forms of propulsion that exist should be used.  One is the traditional chemical booster and the other is the newer ion drive.  ESA's Smart-1 used an ion drive to power its way from Earth orbit to lunar orbit so its a viable technology.  The ion drive can be used for multiple reasons.  It has the power to navigate unmanned craft or failed manned craft (in the case of a dead crew) back to Earth so the loss of assets are minimized.  It can navigate the tug by itself to meet another ship for rescue operations.  It can speed up a manned mission to the moon, or other space bodies, by activating en-route all the way.  So it makes sense to have a dual propulsion system for our reusable space tug.  Of course, it will need a power supply and solar panels should do nicely.  A nuclear power system would be nicer since it could enhance performance and endurance of the craft, but radiating the crew or your cargo or ship is an issue.  Though, the nuclear system could power an artificial magnetic field that provides shielding.  The tug can be used to do all the burns to get from Earth orbit to lunar orbit, and it can get the capsule on its way back to Earth.  After detaching from the capsule, it can change course and get into an elliptical orbit and use aerobraking to slow down the craft to an orbit that is useful for refuel and the next mission thus saving fuel.

Apollo 12 - Intrepid Lunar Module

LEM was the acronym for the lunar lander in the Apollo program.  It meant Lunar Excursion Module.  Later, they just named it Lunar Module but somehow LEM stuck.  A reusable lunar lander would be more appropriate for multiple missions than the one time use LEM.  It could be refueled by the space tug in preparation of a landing and launching back from the surface.  It could be kept in lunar orbit in between missions.  One chemical engine should suffice.  The Apollo LEM was made up of two vehicles: a landing vehicle and a launching vehicle.  For our reusable one, it should be one vehicle.  Perhaps, two lunar landers could provide some redundancy and security for missions.

A single inflatable station module is good to have in orbit around the moon.  Such modules are being developed by Bigelow Aerospace.  It can serve as bigger space and more accommodations for crews, a port for the reusable lander, and a staging place for crew equipment and supplies.  One mission can bring it into orbit with or without a lander to begin with.  More station modules can be added to it as needed.  Boeing had previously suggested EML2 as a place for a lunar station instead of just simple lunar orbit.  I mentioned this plan in my post "Space Exploration Plans From Boeing".  I like the simple lunar orbit exclusively for moon missions over EML2 simply because its closer to the surface and it should take less time and fuel to get to.  Even if that is marginally true, its still viable over the course of many missions or even a campaign.

With capsules, space tugs, landers, and a space station; a commercial effort can carry out many moon missions for various customers.  Thinking about it now, I feel that having a space station around the Moon and a lander would be a good combination for several missions.  Humans have gone to the moon, and many more want to go for various reasons.  Finding way on how to thrive and not just survive on the moon is important for humanity.  We need to spread out beyond Earth.  The moon provides a first step towards that goal.