3.2 Space Propulsion

3.2.1 Warfighter Needs

Integrated High Payoff Rocket Propulsion Technology (IHPRPT). IHPRPT goals translate into payoffs to the warfighter in terms of increased warfighter capabilities. Payoffs to space launch systems include performance, cost, and reliability improvements to existing launch systems, expendable launch systems, and new reusable vehicles. The operational increases for boost and orbit transfer systems by the year 2000, 2005, and 2010 include 9%, 16%, and 22% increases in payload capability for new expendable boosters (over the 25,000 lb baseline to low-Earth orbit (LEO)). An alternative to increasing the payload on a lift vehicle would be to launch payloads on smaller, more capable vehicles to reduce the need for costly heavy-lift vehicles. The resulting launch cost reductions would equate to savings of 19%, 31%, and 42% in cost per pound to orbit. These savings are in addition to the savings seen from design and process changes. For a new reusable launch system, the payload improvements approach 71%, 127%, and 206% over the life of the vehicle by 2000, 2005, and 2010.

Spacecraft goals will result in increased warfighter payoffs through reliable critical information gathering and global communication capabilities at reduced costs. Satellites in geosynchronous orbit will be able to extend their on-orbit life up to 45%, increase repositioning capabilities by a factor of 2 to 5, or increase useful mission payload mass by 10% to 30%. This last capability can mean an ability to increase the number and/or types of transponders, potentially manifest the same payload on less expensive launch vehicles, or increase the survivability of the satellite by allowing for increased shielding material. Communication and reconnaissance satellites will be able to reposition more often and more rapidly to support the warfighter needs in local theaters of operation without significantly sacrificing satellite life. More reliable deployment and on-orbit operation throughout the life of the satellite will provide greater assurance in asset availability. Higher performance compact propulsion systems will also enable the deployment of smaller satellites into higher energy orbits. For medium-lift vehicle class geosynchronous satellites launched at a conservative rate of 6 per year, meeting the IHPRPT goals would result in cost savings of $60 million, $130 million, and $240 million by 2000, 2005, and 2010 respectively.

3.2.2 Space Propulsion

3.2.2.1 Goals and Timeframes. The IHPRPT initiative was started in FY 1994, with primary program impacts beginning in FY 1995. The program is based on achieving the following goals (with respect to 1993 state-of-the-art baselines) for Boost and Orbit Transfer (B/OT) and Spacecraft (S/C). In space platforms the following B/OT and S/C goals exist:

3.2.2.3 Related Federal and Private Sector Efforts. All DoD agencies, NASA, and industry participate in IHPRPT. Industry rocket propulsion IR&D investment for FY95 is approximately $55M. NASA FY95 investment for IHPRPT related programs for the reuseable launch vehicle is approximately $24M.

3.2.3 S&T Investment Strategy

The key to the IHPRPT process is the simultaneous achievement of the goals. Technology demonstrations conducted during each of the three phases will quantify the degree of success in reaching the goals. The technology demonstrators do not have to be a complete propulsion system demonstration. They may be individual components or a combination of components. The requirement is to prove justifiable, analytical connectivity that the compilation of the demonstrated technologies would work together as an acceptable propulsion unit. As a metric, the empirical or analytical data will be compared to baselines identified at the initiation of IHPRPT. Following demonstration, the technologies may transition economically to new propulsion systems or to improvements to current propulsion systems.

3.2.3.1 Technology Demonstrations. Technology Demonstrations for IHPRPT are divided into the three fundamental propulsion classes: (1) Boost and Orbit Transfer, (2) Spacecraft, and (3) Tactical (Tactical is book kept in conventional weapons). Each class is a separate family of demonstrations.

3.2.3.1.1 Boost and Orbit Transfer Propulsion. These demonstrations, when successful, fulfill DTO (SP10). The demonstrators for this mission application area address propulsion systems which lift payloads from ground level to orbit elevation (boost propulsion). Specific boost demonstrations will occur at the end of each IHPRPT phase. In 2000 the component improvements will feed into an integrated powerhead demonstration. In 2005, further component improvements will integrate into a high chamber pressure (4000psi) booster class demo.

3.2.3.1.2 Orbit Transfer Propulsion. These demonstrations, when successful, fulfill DTO (SP11). The demonstrations for this mission application are divided into two areas: chemical propulsion and non-chemical propulsion and address propulsion systems which move payloads from one orbit (such as low-Earth orbit (LEO)) to another orbit elevation (geosynchronous orbit (GEO)). Orbit transfer component improvements will feed into a FY00 high performance (1200psi chamber pressure) upper stage/orbit transfer demo and a FY05 high performance (1500psi chamber pressure) upper stage/orbit transfer demo.

3.2.3.1.3 Spacecraft Propulsion. These demonstrations, when successful, fulfill DTO (SP12). The technology demonstrators for this mission application include two areas: chemical propulsion and non-chemical propulsion, e.g., solar electric and solar thermal. In all cases, these system demonstrations will be conducted at simulated altitude conditions permitting direct measurement of performance at space conditions. Solar electric demonstrations (pulsed plasma thruster and hall thruster) by 2000 and 2005 will integrate all developments for satellite stationkeeping and repositioning. Demonstrations by 2010 will demonstrate advanced solar thermal propulsion systems and advanced solar electric propulsion systems (ion thrusters) for orbit transfer missions.

3.2.3.2 Technology Development. Once the goals and payoffs have been established and confirmed as worthwhile, then the technology advancements needed to achieve the goals are determined. The propulsion technologies in BO/T and S/C are divided into the same four component technology areas. These four areas, which represent the rocket propulsion system technology improvement areas are: propellants, propellant management devices, combustion and energy conversion devices, and control systems. The efforts in the propellant area includes solid, liquid, hybrid, gels, and liner development. Propellant management efforts include work in tanks, feed systems, bladders, turbomachinery, thermal protection systems, cases, pressurization systems, and insulations. Combustion and energy conversion efforts include work in injectors, igniters, combustion chambers, nozzles, gas generators, preburners, and all components of electric and solar propulsion systems (except the propellant). Control system work includes actuator, health monitoring, thrust management, ordnance, valve, and thrust vector control system development.

The projects are technology specific as opposed to being system specific allowing for global propulsion system improvements applicable to all rocket propulsion systems. Goals within each application area address where the research and development specialists will overcome operational deficiencies and meet requirements and needs defined by the propulsion system users. Subsequently, goals are broken down into the component technology improvements needed to fulfill the achievement of the goals. These component improvements are identified and represent component area objectives that the technologists will work towards in laboratory research and development projects.

This goal/objective relationship connects the research and development labs to the user community in a way that streamlines the work done by both communities, and enables the needs of both groups to be satisfied. The result of the IHPRPT process is the fulfillment of a set of goals which integrates the technologists with the user community, and provides maximum payoffs for future space systems.

3.2.3.3 Basic Research. The Phillips Laboratory Propulsion Directorate has several basic research projects supporting development in boost, orbit transfer, and spacecraft propulsion. In boost and orbit transfer, one combustion development project (Supercritical combustion), two propellant development projects (Chemically bound excited states and Non-equilibrium flow characteristics), and three materials development projects for rocket components (Synthesis, Carbon materials research, and Material mechanics research) exist. In spacecraft propulsion, the Plasma diagnostics project supports electric propulsion development.