FIELD JOURNAL

The ICM - an interesting little module

This is my first journal for Space Team Online, and I'm very excited to be a part of this project. I thought today I would tell you a little about why I came out to NASA-JSC to begin with. I was brought here to work on the Interim Control Module, or what we call the ICM. This piece of International Space Station (ISS) hardware was designed to be a backup for the Russian Service Module. That has been my primary project up until now, but since the Service Module (SM) has launched and docked successfully to the ISS, I will begin to work on other projects.

The ICM was originally built by the Naval Research Lab (NRL) in Washington D.C., and was to be used as an inertial upper stage rocket for launching military satellites, out of the space shuttle payload bay, to a higher orbit. This was before the Challenger explosion, January 28, 1986. After the explosion, many things were put on hold and this project was one of them.

When NASA began discussing the idea of a backup for the Service Module, this project (which was not called the ICM then) was considered. Once it was determined that this hardware would work, many modifications had to be made for its new purpose as a space station module.

This module is fairly small compared to other modules of the station. It looks like a squashed disk. It's about the same diameter as the other station modules, but it isn't very long, so there's not much space inside - only enough for its fuel tanks, thrusters and computers. The fuel it uses is hydrazine, which is pretty common, but also pretty nasty stuff. Fueling the ICM isn't as easy as fueling a car, since hydrazine can be very dangerous.

The ICM is to serve two major purposes. The most important purpose is to periodically reboost the ISS into a higher orbit, as the ISS orbit gradually decays (begins to fall in altitude above the Earth). The altitude that the ISS flies at allows enough air that there is not a pure vacuum, though as the altitude gets higher there is less and less air. This allows for a little bit of drag, causing the vehicle's orbit altitude to gradually decay, or get lower.

Up until the time the Service Module went up, we really didn't have a way to reboost the ISS, except with the shuttle when it was docked to the ISS. The ICM has a big reboost engine and can hold lots of fuel. It also has smaller thrusters, which are used for attitude control. Attitude control is being able to point the ISS in a certain direction, and hold it in that position. This is important during reboost, because we want the ISS to thrust in a certain direction. To be able to accomplish these tasks, the ICM had to have its own guidance, control, and computer systems on board.

The neat thing about working with the ICM is that as a flight controller I had to learn many systems, as opposed to only one. I am an ADCO -- which stands for Attitude, Determination and Control Officer - and my job is to control the guidance system for the ISS. For the ICM, I would have been controlling all of its, and many of the ISS, systems - attitude, electrical, computer, thermal, and propulsion.

The ICM is just about finished, and is kept at the NRL. I have had the opportunity to go to Washington D.C. and see the actual space hardware. It is an awesome piece of equipment. What do you think?

The SM only has a limited amount of fuel, so the plan is to use it for reboost as little as possible, using the Russian Progress vehicles (which bring supplies to the station) to reboost when possible since they do have an engine and fuel. Russian Progress vehicles are disposable vehicles. They are launched, docked with the station, their supplies are unloaded, and then after undocking, they burn up on re-entry into the Earth's atmosphere. Again, we will also use the shuttle to reboost when it is docked with the station. Unlike the ICM, the Service Module is the primary living quarters of the station. The crew cannot enter into the ICM.

The ICM may still go up, but the plan at this point would be to launch it about two years from now. There's still quite a bit of planning going on, and of course politics plays a role in many things. That's one of the reasons for having an International Space Station, to benefit from each other's experience and learn to work together as a team. The Russians do some things quite differently from the way we do them, which has called for a lot of compromising. Once ready, the ICM will most likely be stored at Kennedy Space Center. Once a decision has been made to launch it, consumables will have to be replaced (like batteries) and it will need to be fueled. Also, the shuttle's computers would have to be reconfigured for the weight and center of gravity for that particular flight. (This happens with each flight.) We are also still working on some of the software we will use to control the ICM when it does go up.

One of the things I thought was really neat about the ICM is that it uses star tracker cameras to find its location. Just like the sailors of centuries gone by, the ICM uses the stars to figure out where it is and where it's going.