We are planning many flights to the moon; however, one flight has the distinction of being named "the reference mission." This is the flight that places the initial core of the exploration base on the moon. The reference mission also establishes the transportation system we will need to support the lunar base.
We use the reference mission in developing our program plan. By working through the mission, we determine costs, revenues, and technical and political issues to establish that critical foothold on the moon.
Access to Orbit
The Reference Mission starts and ends in low Earth orbit. To get up there, we use launch services developed outside the project.
A host of launchers are available today, and many more are being developed. We selected the Space Shuttle as the launcher for the reference mission because, although it is the most expensive launch system in the world today, it is also by far the most capable man-rated launcher.
Current development of new lower-cost launchers in the United States and other countries will most likely change the situation before the Artemis Project reference mission is ready to launch. Until then, the Shuttle is the best vehicle that can satisfy all our mission requirements. We are being as conservative as we reasonably can in defining the reference mission. If costs and revenues balance using the Space Shuttle, they will look even better with a less expensive launcher.
We are considering many options for getting our crew and hardware to Earth orbit, such as launching the heavy freight on a Titan IV rocket and having the crew ride up aboard a Space Shuttle or a pair of Soyuz space capsules. You will find quite a bit of discussion about all the options in section 126.96.36.199.
In in the original reference mission, two launches put the components of our moon-bound spacecraft into low Earth orbit, where the vehicle is assembled. Our crew goes up with the hardware on the second flight.
Artemis Project Spacecraft
Earth Orbit Servicing Facilities
If the International Space Station is available and the launcher can deliver our spacecraft to it, we plan to use the space station as a staging base. If not, we launch the first element on one flight and then rendezvous with it on the next flight. In that case our crew uses the Shuttle as a staging base for assembling the Artemis Project spacecraft.
We are also studying the alternative of deploying our own staging facility in a low-inclination orbit. This would add quite a bit of cost to the program and delay getting to the moon, but it does have some interesting advantages. The lower-inclination orbit lets us carry about 10,000 pounds more payload per flight than if we go to the International Space Station. It frees us from being tied to the Space Shuttle, which could become very important if the Shuttle or a similar follow-on launcher is not available. It frees from dependence on the International Space Station for a servicing facility in Earth orbit; which opens up our options for how to get to the moon. And it provides the core of a facility in Earth orbit for servincing and refueling our ships for follow-on flights to the moon.
This facility would not free us from our dependence on the technology developed by the Space Shuttle and International Space Station programs. In fact, the Artemis Project would not be possible without the investment that the U.S. taxpayers have already put into these two space programs.
Technical nit: In the illustration, we show two Soyuz spacecraft at the proposed LEO servicing facilities; however, currently there is no way to get a Soyuz spacecraft into a low-inclination orbit. So if we use the Soyuz, we will be back into the same orbital inclination as the International Space Station. This significantly reduces the advantages of an independent facility, especially for the reference mission.
There are three distinct spacecraft in the reference mission: the Lunar Transfer Vehicle, the Lunar Base Core Module, and the Ascent Stage. Section 4.2 of the Artemis Data Book contains all the documents pertinent to design and development of the reference mission spacecraft.
Lunar Transfer Vehicle
The Lunar Transfer Vehicle is a spaceborne habitat with propulsion systems and support for the crew during flight between Earth and the moon. The current design concept for the Lunar Transfer Vehicle uses the Spacehab module as its crew compartment.
The Lunar Transfer Vehicle's design provides for it to be refueled by swapping fuel tanks. We plan to leave it at the space station at the end of the Reference Mission, where it will wait until we launch full fuel tanks for the next flight to the moon.
The Forward Service Module, Aft Service Module, and Propulsion Module are all components of the Lunar Transfer Vehicle. They might be launched as an integrated package or assembled in Earth orbit. The solar panels will be assembled to the vehicle by the crew.
Refer to section 4.2.1 for more information about the Lunar Transfer Vehicle.
Lunar Exploration Base and Descent Stage
The Descent Stage is a propulsion package attached to the core module of our lunar exploration base. These rockets are used only one time, to land the habitat on the moon. After the landing, the fuel tanks might be used for storing oxygen mined from the lunar regolith.
The exploration base manned element is based on using three Spacehab modules connected in tandem. This configuration was suggested by Spacehab, Inc., based on their experience with flying a double module on Space Shuttle flights to the Mir space station in 1997 and 1998. The three modules give us enough volume to expand our lunar base without the need to land additional pressurized modules for the first several flights to the moon.
When the lunar exploration base lands on the moon, it is stacked vertically above the Descent Stage. Once on the moon, it drops a foot and rotates into the horizontal position. The horizontal orientation gives us a much more efficient interior layout than if we had left the the exploration base stacked vertically.
We want to leave as much mass on the surface of the moon as we can, so we've stripped the Ascent Stage down to the bare minimum. It a simple, open vehicle, just enough to lift the crew and a couple hundred pounds of moon rocks from the lunar surface. The crew flies the Ascent Stage to lunar orbit, where they make their rendezvous with the orbiting Lunar Transfer Vehicle.
Our crew will fly the Ascent Stage with just their space suits for protection. They even leave their backpacks on the moon. At first glance, this might seem like risky business, but the crew will not risk any greater danger during this flight than they would spending a couple of hours outside the lunar exploration base.
See section 4.2.4 for more information about the Ascent Stage.
These three spacecraft make up the stack we fly to the moon. After the stack is assembled at the space station, the lunar transfer vehicle's rockets are used to fly to the moon and enter orbit about 60 miles above the lunar surface. The reference mission uses a trajectory similar to the Apollo flights.
Upon arrival in lunar orbit, the lunar base habitat with its descent rockets separates from the lunar transfer vehicle and lands on the surface of the moon.
Our landing site for the reference mission is an area of Mare Anguus we have dubbed "Angus Bay." We even have a document in the Artemis Data Book that explains How Angus Bay got its name.
On a map of the moon, you'll find this area just northeast of Mare Crisium. In Earth's northern hemisphere, you'll see a dark spot near the top of the moon as it rises in the east. That dark spot is Mare Crisium. Our landing site is just at the top of that dark spot.
See section 188.8.131.52 for more information about Angus Bay and how we chose this as the landing site for the reference mission.
The lunar transfer vehicle remains in its orbit around the moon while our crew takes the lunar exploration base down to the surface. Advances in automation technology and guidance and control systems since the Apollo program allow the lunar transfer vehicle to remain unmanned while the crew delivers the exploration base to the moon. Automated guidance can handle the necessary orbit circularization and plane change without the need for a human on board. This eliminates the need to fly a separate LTV pilot, and allows all crewmembers to go down to the moon.
On the moon, the crew levels the lunar base core. After landing vertically, the descent stack drops a foot at the end of a long truss to brace against, and then the core module rotates into position. See the essay on Landing Day Operations for more description of how this works.
The crew conducts extravehicular activity to assay the site and gather samples of the lunar regolith (moon dirt). The crew also sets up cameras to get stock footage of the site and their activities, as well as to record their ascent and the arrival of the next flight. (They film activities throughout the flight, both stock footage and scripted scenes for later use in movies and documentaries.)
When surface activities are complete, the crew boards the ascent stage for a two-hour flight to rendezvous with the orbiting lunar transfer vehicle. During the flight our crewmembers depend on their space suits for life support. The flight should pose no greater hazard to the crew than two hours of surface EVA.
After docking the ascent stage to the LTV, our moon explorers return to Earth orbit. Unlike the Apollo astronauts, they do not enter directly into Earth's atmosphere. Instead, they expend more fuel to brake their trajectory and enter Earth orbit for a rendezvous with the International Space Station.
Carrying fuel for the final braking to Earth orbit reduces the size of the base we can leave on the moon, but there are several advantages which appear to outweigh that cost. By leaving the transportation system in orbit for use on later flights, we lower the cost of future development. It also reduces the cost of the initial flight by eliminating the need to develop a vehicle which can operate in the atmosphere, and trades the weight of the additional fuel for the weight of the heat shield which would be required for atmospheric entry.
An alternative to using rockets for braking to Earth orbit would be to use a heat shield as an aerobrake; however, aerobraking technology is still in the early development stage and the expense of developing it is beyond the anticipated capital resources of the Artemis Project.
At the space station, the crew secures the LTV and ascent stage. The LTV may be used at the space station for additional laboratory space between flights, or it may be leased for other space operations. Among the proposals we've received is to fly the LTV on a mission to a Near-Earth Asteroid. With additional fuel tanks plus food and air for the crew, it could perform this mission with little modification.
See section 5.4 for more on alternative missions for the Lunar Transfer Vehicle.
Once the Artemis Project vehicles have been secured at the space station, the crew returns to Earth on the next available Shuttle flight. It is possible (but not necessary) to conduct the entire moon flight in one Shuttle flight, with the crew flying to same orbiter up and then back down to Earth's surface.
The mission is not over once the crew goes home. To survive the cold, two-week-long lunar night, the moon base will need a lot of insulation. By burying the core module in moon dirt, we provide the necessary insulation as well as protection from radiation and meteoroids. A robot rover, landed ahead of the initial lunar base, is included in the mission plan for this purpose. Since the lunar base can survive several lunar nights using just its heaters, this machine does not need to be very large. We can take several months to lay a blanket over the habitat.
See section 4.2.5 for more on the robotic attendants to the Artemis Project reference mission.
With this robot, we may also be able to photograph our spacecraft's initial descent to the lunar surface. This will be the first time any vehicle has been recorded landing on the moon.
Afterward: I borrowed most of the spaceship pictures in this document from the post cards available from Lunar Traders. (They also carry a magnificent full-color poster depicting the Reference Mission and all the spacecraft.) All the spacecraft images are copyright © 1998 by Vik Olliver; all rights reserved. Spacecraft designs are Copyright © by and trademarks of The Lunar Resources Company. Used by permission.