Hypersonic Airplane Space Tether Orbital Launch (HASTOL) system - Interim study results

Abstract

The Hypersonic Airplane Space Tether Orbital Launch (HASTOL) system is a novel architecture for an Earth-toorbit launch system consisting of: a completely reusable airbreathing subsonic-to-hypersonic dual-fuel airplane which transports the payload from the ground to some intermediate point in the upper atmosphere; an orbiting spinning space tether system which picks up the payload from the intermediate point and takes it on into orbit; and a grapple assembly for transferring the payload from the hypersonic airplane to the lower end of the space tether. The system is revolutionary in that it minimizes, and perhaps even eliminates, the use of rockets for Earth-to-orbit launch of satellite payloads and even passengers. For the hypersonic airplane portion of the HASTOL system we use an existing Boeing design for the DF-9, a dual-fuel ah-breathing launcher that has benefited from over a million dollars in NASA/LaRC and Boeing funding during prior study efforts. The DF-9 has a 9 m (30 ft) long by 3 m (10 ft) diameter upward-opening central payload bay that can handle payloads up to 14 Mg (14 metric tons or 30,000 lb). With a full fuel load at takeoff, the hypersonic airplane masses approximately 20 times the payload mass, and can deliver the payload to 100 km (330 kf-t) altitude at an apogee speed of 3.6 km/s (12 kft/s) or approximately Mach 12. For the space tether portion of the HASTOL system, there are a number of design options, all of which will work, although some options promise better performance. The tethers can be built today using presently available commercial fibers. The tethers are long, typically 400 to 1600 km (1300 to 5300 kfi) in length. The total mass of the space tether plus the Tether Central Station typically will be 30-200 times the payloads being handled. Most of that mass ratio requirement is driven by the fact that the tether system must mass considerably more than the payload it is handling, so that, upon pickup of the payload by the tether, the payload will not pull the space tether system down into the atmosphere. Thus, the advent in the future of better tether materials with higher strength at higher temperatures will not be used to lower the tether system mass significantly, but instead will be used to increase the tether safety margins,’ lifetime, and system performance, by allowing payload pickup at lower altitudes and lower speeds, thus decreasing the performance requirements on the hypersonic airplane portion of the system. INTRODUCTION The Boeing Company, Tethers Unlimited, Inc. (TUI), HASTOL Architecture and the University of Maryland, have teamed to study the feasibility of a completely new concept for moving payloads and passengers from the surface of the Earth into low Earth orbit at low cost and low acceleration levels without the use of rockets as the main source of propulsion. Our joint study effort, funded by a $75,000 Phase I grant from the NASA Institute for Advanced Concepts, is halfway through its 6-month term. This paper builds upon work reported in a previous paper’, and should be considered an interim report of the study results to date, rather than a finished piece of work. Copyright