Lead ion collision C014/1793
Particle tracks from a lead ion collision seen by the CMS (compact muon solenoid) detector at CERN (the European particle physics laboratory) near Geneva, Switzerland. Before the collision the ions had been accelerated by the large hadron collider (LHC). The central tracking chamber (cylindrical) and muon chambers (red rectangles) of the detector are seen end-on in outline. The collision produced a number of unidentified particles (orange) and an upsilon meson. The upsilon meson is not seen, but is revealed through its decay products; a pair of muons (two longest red lines). The green lines show the energy deposited by the muons in the detector's muon chambers. The energies of the unidentified particles are measured by the electrochemical calorimeter (shorter red lines) and the hadron calorimeter (blue)
© CMS EXPERIMENT, CERN/SCIENCE PHOTO LIBRARY
Lunar cycler centrifuge
A living quarters module, secured to the end of a centrifuge boom, swings into the foreground while an unmanned cargo ship prepares to dock in the upper left. Both are falling toward the moon at a leisurely 1, 500 miles per hour. On the upper right abutting the orange propellant tanks, is the blue glow of one of the cycler's four ion engines. These engines may be all that's required to maintain the long-term integrity of the cycler's orbit.
Studies have shown that human health can suffer in the absence of gravity. Physiological hazards include loss of bone mass and diminished cardiovascular performance. While regular exercise can mitigate microgravity's deleterious effects, it may be determined that the best therapy would be a simulated gravity environment. Unfortunately nature appears to offer few options for simulating gravity, however a technologically feasible solution would be the employment of a centrifuge.
A centrifuge is a mechanical device that puts an object in rotation around a fixed axis, resulting in a gravity-simulating force perpendicular to the axis. Small scale centrifuges are used on Earth to quickly separate substances of varying density. In the microgravity of space, a large centrifuge could be constructed, not to separate substances, but to simulate gravity for human occupants. In the image above envisions a centrifuge with two booms, each with a radius of 100 feet, and each secured to a living quarters module with accommodations for six. A rotation rate of two revolutions per minute would generate a force equal to one-sixth the gravitational force at the Earth's surface, which happens to be that of the moon's.
Given the enormous engineering challenges, it would have to be demonstrated that even a force of one-sixth the Earth's gravity would go a long way toward ensuring human health. (Of course, larger centrifuges have been envisioned, from the massive two-wheeled space station in the movie 2001: A Space Odyssey, to a tethered version with a radius of a half-mile under consideration for Mars missions.)
While spinning a centrifuge at a faster rate would simulate a greater gravitational force, in this case the 100 foot radius would result in a force gradient that could cause its own physiological hazard, i.e. standing humans would experience a noticeably greater gravitational-like force at their feet than at their heads
© Walter Myers/Stocktrek Images
Artists concept of a lunar cycler
A lunar cycler has reached its furthest orbital point from the Earth, the apogee, and is rounding the far side of the Moon to begin its fall back toward Earth. At apogee the lunar cycler is about 300 thousand miles from the Earth and 50 thousand miles beyond the orbit of the Moon (further from Earth than any human has ventured yet). Based upon what may be technologically feasible within the next 75 years, this is a suggestion of what a lunar cycler might one day look like. This cycler would be 200 feet long (about the height of a 20-story building) and accommodate 12 passengers and crew. A 200 foot centrifuge bisects the cycler tower and provides artificial gravity for the wayfarers.
If frequent manned trips to the Moon become a reality, the earlier throw-away technologies of the Apollo lunar missions will be impractical for the long term. More efficient and reusable systems will need to be developed in order to minimize the labor and resources required for these extraordinary voyages.
A journey to the Moon can be broken down into three basic tasks: transfer between the Earth's surface and Earth orbit, transfer between Earth orbit and lunar orbit, and transfer between lunar orbit and the Moon's surface. While the simplest solution may be a single vehicle that could do all three, no technology today or in the foreseeable future can meet all these needs. One solution would be to dedicate separate vehicles for each of the three tasks. A reusable space shuttle would lift explorers off the Earth's surface, a dedicated and reusable lunar shuttle would deliver explorers to the Moon's surface and back, and in between there would be a kind of orbital way station. One such way station is known as an orbital cycler.
An orbital cycler is a vehicle that's in a permanent orbit around two celestial masses. In the case of a lunar cycler, the orbit would encompass both the Earth and the Moon. One lunar cycler proposal would place the cycler in a highly elliptical Earth/Moon orbit. The lunar cycler would complete an orbit every two weeks, and make a close approach to the Moon every other orbit. The cycler journey from the Earth to the Moon would take about a week
© Walter Myers/Stocktrek Images