SHERPA: a responsive multi-mission space tug
The shuttle expendable rocket for payload augmentation (SHERPA) is a rocket-powered orbital transfer system for small satellites. It is currently being developed by the Air Force Research Laboratory Space Vehicles Directorate (AFRL/VS) to support the need of the Department of Defense (DoD) space test program (STP) to deploy satellite payloads to higher orbits. SHERPA, a space tug, mass of 56 kilograms and is capable of boosting a 125-kg satellite payload from an orbit of 350 kilometers to 700 kilometers. The STP utilizes a variety of systems to fly its payloads. Although the current plan for the SHERPA flight demonstration is to use the canister for all payload ejections (CAPE), opportunities exist to also launch as a secondary payload aboard an expendable launch vehicle (ELV). The SHERPA team, consisting of AFRL/VS and several small business innovative research (SBIR) contractors, is designing the core technologies for this effort to be as modular as possible to allow use of these individual technologies in other applications. The planned demonstration SHERPA fly as a secondary payload and deploy after the space shuttle has completed its primary mission. After SHERPA and its satellite payload have separated from the Shuttle, it loiters on orbit until it is adequately separated from the shuttle and international space station (ISS). The SHERPA orient the payload stack and fire its propulsion system to enter a Hohmann transfer orbit. This boost requires a total change in velocity of 240 meters per second (m/s) and includes a one-degree plane change for collision avoidance. After the stack has coasted to the final mission orbit apogee, the propulsion system fires again, inserting the satellite payload into its final mission orbit. SHERPA will then separate itself from the satellite payload and fire a collision/clearance avoidance maneuver (C/CAM), ensuring it is clear of the satellite and guaranteeing the pressurized propulsion tanks are emptied as much as possible before re-entry. After this final maneuver, SHERPA is in its lowest possible orbit and ready for rapid re-entry.
SHERPA: A Flexible &amp; Responsive Small Satellite Transport Vehicle
SHERPA1,2, the Shuttle Expendable Rocket for Payload Augmentation, is a highly capable propulsive satellite. The SHERPA is currently approaching a PDR level design. The SHERPA can perform a wide range of missions including orbit transfers, small satellite maneuvers, space situational awareness missions, and serve as a platform for experiments. The SHERPA has three versions: The Mark I, is a propulsion unit, the Mark II is a standalone propulsive satellite, and the Mark III, a self contained long-duration propulsive satellite. Each version can support either an electric or chemical propulsion module. The SHERPA integrates several Air Force Research Laboratory developed technologies into one unique package. The SHERPA can also fulfil a number of other mission needs as a low cost satellite bus for the DoD Space Test Program
The REX-ISOLDE project
The Radioactive Beam Experiment REX-ISOLDE [1–3] is a pilot experiment at ISOLDE (CERN) testing the new concept of post acceleration of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration of the highly charged ions in a short LINAC using modern ion accelerator structures. In order to prepare the ions for the experiments singly charged radioactive ions from the on-line mass separator ISOLDE will be cooled and bunched in a Penning trap, charge bred in an electron beam ion source (EBIS) and finally accelerated in the LINAC. The LINAC consists of a radiofrequency quadrupole (RFQ) accelerator, which accelerates the ions up to 0.3 MeV/u, an interdigital H-type (IH) structure with a final energy between 1.1 and 1.2 MeV/u and three seven gap resonators, which allow the variation of the final energy. With an energy of the radioactive beams between 0.8 MeV/u and 2.2 MeV/u a wide range of experiments in the field of nuclear spectroscopy, astrophysics and solid state physics will be addressed by REX-ISOLDE.