Could the International Space Station (ISS) serve as a repair hangar for satellites or a way station for craft headed beyond its orbit?
Jack Bacon of the Mission Analysis and Integration Group at NASA's ISS Program Integration Office explains:
Repairing satellites onboard the ISS may prove impractical, but chances are better for the way-station option. The main issue with repair is that a service platform must start in the same orbital plane as the satellite, and the chances are slim that any particular satellite would meet that condition. Even a one-degree orbital plane change to meet a satellite would cost the station nearly 12 metric tons of propellant, and most satellites are much farther inclined to the ISS's orbit than just one degree. Similarly, most satellites do not have the propellant available to change their own orbital plane, so they cannot come to the station.
Working on a spacecraft inside the ISS also presents real problems. Every craft deploys instruments and valves using pyrotechnic mechanisms once it reaches orbit, but it is unwise to have unexploded pyrotechnics in a so-called shirt-sleeve environment, and, conversely, it is difficult to fit a fully deployed spacecraft inside. Astronauts do not have the same unlimited supply of fresh air that workers on the ground enjoy, so any toxic risk (such as propellant) is potentially catastrophic.
Even if we chose to accept the risks, we would face the final hurdle of how to build a chamber wide enough or a doorway strong enough to accommodate a large spacecraft. The aerodynamics of launch vehicles limits the diameter of the payload (or chamber) to about five meters. Even assuming we worked with only a few centimeters of clearance between the spacecraft and the walls, we would still have the problem of getting the spacecraft in and out of the chamber. A five-meter hatch must withstand nearly 200 tons of force, requiring some massive framing and hardware that would further complicate the design, building and launch processes.
The prospects are much more favorable for using the station as a staging base for further deployment of spacecraft that leave Earth's orbital environment, such as the James Webb Space Telescope and missions to the moon or Mars. But such outfitting would need to be done in the vacuum of space with the spacecraft docked to the station. In any case, the launch window to the moon, Mars or other points would occur far less often from the station than the ground.
Can a dose of testosterone produce an improvement as immediate and profound as that which Floyd Landis showed in the 2006 Tour de France? —R. Abt, Meadowbrook, Pa.
Michael S. Bahrke, co-editor of the 2002 book Performance-Enhancing Substances in Sport and Exercise (Human Kinetics Publishers), replies:
A single dose of testosterone most likely would not produce a quick recuperative effect resulting in a sensational turnaround in performance.
During the Tour de France race, Landis's ratio of testosterone to epitestosterone (an inactive steroid usually found in roughly equal abundance to testosterone), the so-called T/E ratio, tested higher than 4 to 1, the limit considered by the World Anti-Doping Agency as proof of steroid use. Because Landis previously tested within the acceptable bounds, speculation as to why a sudden spike occurred centered on his possible use of a testosterone patch or gel. (This past September, Landis lost his appeal of the result and was stripped of the 2006 Tour title.)
Research indicates that large doses of testosterone can significantly increase muscular strength within six to 12 weeks of administration, and one recent study found significant effects after just three weeks of use; further testing is needed to determine what, if any, shorter-term effects testosterone provides. In other words, testosterone would not be used for recovery and increased work output during a single Tour stage, but if taken early and long enough, it would be beneficial for maintenance and improved performance over the course of the entire 22-day race.