Alternative LTV Missions
Section 5.4.
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Summary of Alternative Missions for the Lunar Transfer Vehicle

Earth orbit research laboratory

Since the LTV's docking mechanisms are compatible with those used on the International Space Station, it can be attached to the space station for use as additional laboratory space. Its interior outfitting will accommodate standard space station payload racks, and its windows provide opportunities for Earth observation.

LEO free-flyer

The LTV can also fly free in low Earth orbit, supporting its crew for a week or more of Earth observation. During these missions it can also be used in conjunction with NASA's manned maneuvering unit to recover or repair satellites in low Earth orbit with no modification.

Geosynchronous satellite servicing

Geosynchronous orbit is that circular orbit around the Earth where we park most of our communications satellites. Flying a crew to and from geosynchronous orbit is certainly within the propulsion capabilities of the LTV; however there is a problem: Earth's radiation belts. In its reference mission, the LTV passes through the radiation belts very quickly, exposing the crew to a maximum dose of 1 REM of radiation. To put that into perspective, NASA's 30-day exposure limit is 25 REM. Workers on Earth are limited to 5 REM/year, and the median lethal dose is 450 REM.

To remain for any length of time inside the radiation belts, the crew will have to be heavily shielded. Even their space suits will require extra shielding. This doesn't make it impossible to service communications satellites in geosynchronous orbit, but it does mean additional development and experimentation will be required before we can commit the LTV to this kind of mission.

Near-Earth Asteroids

Hundreds, perhaps thousands, of metal-rich asteroids orbit the Sun near the Earth. An article in the Journal of Geophysical Research estimated that a kilometer-sized metal bearing Near-Earth Asteroid contains up to 400,000 metric tons of platinum-group metals. Those metals would command a price of 5 trillion dollars at current U.S. market prices; however, the article points out that flooding the market with this much metal would reduce the market value to 320 billion dollars.

That's still an incredible economic incentive to explore these asteroids. The DV required to rendezvous with and explore a near-Earth asteroid is actually less than that required to land on the moon. The mission would be longer -- perhaps as long as nine months -- so the logistics of providing life support for the crew become more complex. We would want to add closed-loop systems for water and atmosphere. The total vehicle weight grows, and with it the fuel requirements. The additional fuel can be accommodated in strap-on tanks, located over the crew compartment to provide additional radiation shielding.

In contrast to the geosynchronous orbit mission, radiation is less of a problem for an asteroid exploration flight. The primary radiation concern is the Galactic Cosmic Radiation dose the crew will receive, with the additional likelihood of an anomalously large solar flare event. The crew can be protected from a solar flare by providing a region of massive shielding -- most likely the main engine compartment with all its tanks and plumbing -- which can be oriented toward the incoming proton flux.

Circumlunar flight

Finally, one proposed mission for the LTV can be carried out with no modification at all to the vehicle: a trip to lunar orbit similar to that of Apollo 8. While it has been done before, it hasn't been done for a long time, and we will be able to make this exciting flight even before the other Artemis vehicles are completed. In addition to generating a tremendous amount of publicity for the project, such a flight would be a shake-down cruise for the LTV, the crew, and the flight support team here on Earth.

Alternative LTV Missions

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