## Session

Session III: Bold New Missions Using "Breakthrough Technologies" II

## Abstract

It is well-known that prolonged exposure in humans to a microgravity environment leads to significant loss of bone and muscle mass; this presents a formidable obstacle to human exploration of space, particularly for missions requiring travel times of several months or more, such as a 6 to 9mon th trip to Mars. Artificial gravity may be produced by spinning a spacecraft about its center of mass, but since the g– force generated by rotation is equal to “omega-squared times r” (where omega is its angular velocity and r is the distance from the center of rotation), we have that unless the distance from the center of rotation is several kilometers, the rotation rate required to generate “1 − g” would induce vertigo in the astronauts as they moved about the capsule (e.g. if the distance from the center of rotation is 10 meters, the required rotation rate for 1 − g would be 9.5 rpm). By tethering the crew capsule to an object of nearly equal mass (such as the spent final rocket stage) at a distance of 1 to 2 kilometers, the necessary rotation rate would be sufficiently small as to not cause discomfort for the astronauts. For example, if the distance from the center of rotation is 2 kilometers, the required rotation rate for 1−g would be 0.67 rpm; at 1 kilometer the rate is still only 0.95 rpm. 1 rpm is considered an acceptable spin rate for the human body to withstand for extended periods of time. This paper gives an overview of the Tethered Artificial Gravity (TAG) satellite program, a 2-part program to study the operation and dynamics of an artificial-gravity-generating tethered satellite system. Phase I of the program will culminate in a flight of a model spacecraft in a non-ejected Get-Away-Special (GAS) Canister on the Space Shuttle. It is to be operated under the aegis of the Texas Space Grant Consortium. The purpose of the Phase I flight is to test key components of the system to be flown in Phase II of the program. Phase I will also involve detailed modeling and analysis of the dynamics of the spacecraft to be flown in Phase II of the program; the Phase II spacecraft will be a small, 65 kg, tethered satellite system which will be boosted into low-earth orbit, deployed and then spun-up to produce artificial gravity. In addition to a description of the TAG program, results of parametric studies related to TAG will be presented in this paper.

A Small-Satellite Demonstrator for Generating Artificial Gravity in Space via a Tethered System

It is well-known that prolonged exposure in humans to a microgravity environment leads to significant loss of bone and muscle mass; this presents a formidable obstacle to human exploration of space, particularly for missions requiring travel times of several months or more, such as a 6 to 9mon th trip to Mars. Artificial gravity may be produced by spinning a spacecraft about its center of mass, but since the g– force generated by rotation is equal to “omega-squared times r” (where omega is its angular velocity and r is the distance from the center of rotation), we have that unless the distance from the center of rotation is several kilometers, the rotation rate required to generate “1 − g” would induce vertigo in the astronauts as they moved about the capsule (e.g. if the distance from the center of rotation is 10 meters, the required rotation rate for 1 − g would be 9.5 rpm). By tethering the crew capsule to an object of nearly equal mass (such as the spent final rocket stage) at a distance of 1 to 2 kilometers, the necessary rotation rate would be sufficiently small as to not cause discomfort for the astronauts. For example, if the distance from the center of rotation is 2 kilometers, the required rotation rate for 1−g would be 0.67 rpm; at 1 kilometer the rate is still only 0.95 rpm. 1 rpm is considered an acceptable spin rate for the human body to withstand for extended periods of time. This paper gives an overview of the Tethered Artificial Gravity (TAG) satellite program, a 2-part program to study the operation and dynamics of an artificial-gravity-generating tethered satellite system. Phase I of the program will culminate in a flight of a model spacecraft in a non-ejected Get-Away-Special (GAS) Canister on the Space Shuttle. It is to be operated under the aegis of the Texas Space Grant Consortium. The purpose of the Phase I flight is to test key components of the system to be flown in Phase II of the program. Phase I will also involve detailed modeling and analysis of the dynamics of the spacecraft to be flown in Phase II of the program; the Phase II spacecraft will be a small, 65 kg, tethered satellite system which will be boosted into low-earth orbit, deployed and then spun-up to produce artificial gravity. In addition to a description of the TAG program, results of parametric studies related to TAG will be presented in this paper.