Benefits of a Single-Person Spacecraft for Weightless Operations

Abstract

Historically, less than 20 percent of crew time related to extravehicular activity (EVA) is spent on productive external work.1 A single-person spacecraft with 90 percent efficiency provides productive new capabilities for maintaining the International Space Station (ISS), exploring asteroids, and servicing telescopes or satellites. With suits, going outside to inspect, service or repair a spacecraft is time-consuming, requiring pre-breathe time, donning a fitted space suit, and pumping down an airlock. For ISS, this is between 12.5 and 16 hours for each EVA, not including translation and work-site set up. The work is physically demanding requiring a day of rest between EVAs and often results in suit-induced trauma with frequent injury to astronauts' fingers 2 . For maximum mobility, suits use a low pressure, pure oxygen atmosphere. This represents a fire hazard and requires pre-breathing to reduce the risk of decompression sickness (bends). With virtually no gravity, humans exploring asteroids cannot use legs for walking. The Manned Maneuvering Unit offers a propulsive alternative however it is no longer in NASA's flight inventory.FlexCraft is a single person spacecraft operating at the same cabin atmosphere as its host so there is no risk of the bends and no pre-breathing. This allows rapid, any-time access to space for repeated short or long EVAs by different astronauts. Integrated propulsion eliminates hand-over-hand translation or having another crew member operate the robotic arm. The one-size-fits-all FlexCraft interior eliminates the suit part inventory and crew time required to fit all astronauts. With a shirtsleeve cockpit, conventional displays and controls are used and because the work is not strenuous no rest days are required. Furthermore, there is no need for hand tools because manipulators are equipped with force multiplying endeffectors that can deliver the precise torque for the job.

Optimization of multi-arm robot locomotion to reduce satellite disturbances during in-orbit assembly

“…For astronauts, systems such as the Manned Maneuvering Unit (MMU) [10] provide a jetpack-like vehicle that allows the astronaut to fly freely in space. These concepts are still under evolution, for instance with the NASA study FlexCraft [11].…”

“…where F r ∈ R 6 contains the wrenches acting on the robot frame, and M, C ∈ R 12×12 are the matrices of inertia and Coriolis/centrifugal terms, respectively. Note that in (11), F r creates a counter wrench on the platform due to the holonomic constraint in (8).…”

An evolvable space telescope configured for NASA's Habex mission: the initial stage of LUVOIR

“…x 'Near' being defined based upon each individual scenario. from large spacecraft xi (perhaps on a similar scale as the Gateway) to small free-flying robots to crewed single person spacecraft 43 (SPS -see Figure 17) to individual astronauts whose "spacecraft" would simply be their spacesuit. Vehicles as small as cubesats could be used for (among other applications) close inspections and metrology to ensure high quality of servicing by other spacecraft, and there may even be roles for highly miniaturized 'Chipsats' to repair electronic systems, modify spacecraft surfaces to enhance thermal control and replace failed solar cells, or the like.…”