Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Appendix L: Tether Boost Facility Design Final Report5.1 Ground Based Rendezvous and Capture DemonstrationRendezvous and capture is a technology that needs to be investigated to validate acritical element of the MMOSTT operational concept. Traditional space vehiclerendezvous and capture (R&C) scenarios take place over span times of several minutesto several hours. In the case of a momentum exchange tether architecture, therendezvous and mating of the tether tip and the payload needs to take place in minutes.There are mere seconds of time during which the tether tip and payload are in closeenough proximity to rendezvous and successfully complete a docking operation. This isabout two orders of magnitude less time than traditional space docking scenarios.At first glance, rendezvous and dock of two orbiting space assets in this short amount oftime seems unthinkable. However, one needs to recognize that the two assets havevery predictable paths, and if designed properly with the appropriate sensor, tracking,communication, and perhaps propulsion subsystems, the two assets can cooperate toaccomplish the maneuver. To our knowledge, this scenario timeline has not beeninvestigated, nor have any systems been designed to accomplish rapid rendezvous anddock.Background. Boeing and TUI are presently studying space tether and payloadrendezvous and capture as part of the NIAC funded Hypersonic Airplane Space TetherOrbital Launch (HASTOL) program. HASTOL is a reusable launch architecture thatdelivers a payload from the earth surface to a sub-orbital altitude, using a hypersonicaircraft, at which point it meets the tip of a rotating space tether. An assembly at thetether tip grapples the payload, and the tether continues to rotate, boosting the payloadto orbit. Although the MMOSTT and HASTOL architectures are different, theirrendezvous and capture scenarios have many similar characteristics.The objective of the HASTOL R&C task is to develop and utilize a digital simulation todetermine the preliminary R&C requirements for sensor, propulsion, and communicationsubsystems for each architecture element, which include the grapple, the tether, thedelivery aircraft, and the payload. Ideally, the aircraft will be guided, or flown, to therendezvous point, using it’s own navigation algorithms and tether tip and grappleposition information that will be downlinked to the aircraft. However, trade studies willbe performed to determine if aircraft maneuvering is the most effective way tosuccessfully bring the payload to the tether tip, such as active maneuvering of thegrapple. Once the preliminary R&C requirements have been established, a preliminarygrapple concept can be developed and the required subsystems can be identified.At the end of the HASTOL contract, we expect to have preliminary rendezvous andcapture requirements defined and preliminary concepts for the grapple, its subsystems,and any subsystems that need to be incorporated to other HASTOL system elementsfor successful payload and grapple rendezvous and capture. The HASTOL simulationmodel, grapple, and other system element requirements and subsystems can then beadapted to the MMOSTT architecture, thus serving as a point of departure for moredetailed analyses and configuration design in follow-on programs.F-24