Technical Briefing

Small Business Innovation Research (SBIR) Focused Topic

Near term objective and vision: Commercialization of monopropellants and related technologies that are safer, higher energy, and higher density for small spacecraft, upper stages, and vehicle reaction control systems. Far term objective and vision: Commercialization of high energy density propellants and related technologies that provided higher density, high energy, and improved operability for Reusable Launch Vehicles.

• Critical technologies:
  • Monopropellant fuel development
  • Propellant operations and safety
  • Hypersonic fuel development
  • High energy density propellant formulations
  • Large scale booster applications

Monopropellant Fuel Development

• Development of new monopropellants for use in space vehicles is desired
• Envisioned as high density monopropellant that are self pressurizing with high safety and low toxicity
• Primary markets for the technology are:
  • Upper stages
  • Vehicle reaction control subsystems
  • On board propulsion for small spacecraft
• Seek monopropellant with:
  • High performance
  • Environmental safety
  • Self pressurization
  • High density
• Materials compatibility, high temperature coatings and cooling techniques, and ignition systems sought
• Monopropellant technology issues – HAN-based fuels
  • Ignition systems
    • Electrical, catalytic, or laser
    • Catalyst materials must resist oxidation (refractory substrate)
  • High temperature chamber coatings
    • Higher temperature operation with high water content in exhaust
    • Highly oxidizing environment
  • Material compatibility (propellant tankage, lines, etc.)
    • Fuel components react with metals, requiring plastic or elastomeric liners, material passivation, coatings
  • SBIR focused topic will provide innovative solutions

Propellant Operations and Safety

• During the development of the propellants described in the other subtopics, the safety of these propellants must be assured
• Testing of these propellants for safety is a generic requirement for successful integration into flight systems
• Propellants that enhance safety of rocket systems are typically composed of environmentally safe materials (water, HAN, etc.) or are gelled fuels that are easily contained after a spill
• This subtopic is seeking creation of:
  • More easily handleable propellants
  • Improvements to make propellants safer (gelling, microencapsulation of metal particles, etc.)
  • Propellants that allow shorter processing times

O2 /H2- and H2-Powered Vehicles

• Primary benefits
  • Higher density hydrogen – 10 percent increase (typical) and density can be adjusted for selected missions
  • Reduced boiloff rate – factor of 2 to 3 reduction
  • Safety – leak potential reduced
  • Increased specific impulse (in some cases)
• Primary applications
  • Highly Reusable Space Transportation
    • Airbreathing vehicles
    • All rocket SSTO: main engines and RCS
  • Affordable In-Space Transportation
    • Solar thermal rockets
    • Upper stages and orbital transfer vehicles

Gelled Propellant Assessments to Find the Best Applications

• Systems analyses for future vehicles and missions
  • Higher density hydrogen, and other fuels
  • Increase safety
  • Reduced boiloff
  • Reduced sloshing
  • Increased specific impulse (in some cases)
• Critical proof of concept experiments
  • Boiloff reduction in large scale experiments
  • Density and stability of gelled fuels with different gellants, gellant percentages
  • Gelled hydrogen combustion efficiency

Hypersonic Fuel Development

• With the planned development of:
  • Reusable Launch Vehicles
  • Airbreathing Rocket Based Combined Cycle
  • Combination propulsion systems
• Higher density fuels will be desirable
• Higher heat capacity fuels will be desirable
• Foster development of fuels for airbreathing vehicles in the speed range of Mach 1 to 25
  • Endothermics
  • Gelled hydrogen
  • Feed system components
  • Fuel system development and testing

Gelled Hydrogen for Airbreathing – H2-Powered Vehicles

• Primary benefits
  • Higher density hydrogen – the volume of an airbreathing vehicle with H2 is primarily the H2 tank
  • A 10 percent density increase allows significant reduction in tankage volume, structural mass, thermal protection system (TPS) area and weight
  • All together, these savings significantly reduce vehicle mass and size (based on past results)
• Primary applications
  • Highly Reusable Space Transportation
    • Airbreathing vehicles
  • Other H2 engine airbreathing applications – RBCC, etc.

High Energy Density – Propellant Formulations

• The overarching vision is to create a propellant combination which has at least the performance of O2 /H2 (typical of the Space Shuttle, which delivers a specific impulse of 452 seconds in vacuum) but with higher overall propellant density
• Formulation of high energy density materials (HEDM) requires use of sophisticated computer modeling to guide the experimental production
• Current materials of interest are:
  • Cubane
  • Strained ring compounds
  • Polymeric Oxygen (O4, O6, O8…)
  • Polymeric Nitrogen (N4, N6, N8…)
  • BH2, BH4, and B-N analogs of prismane (B3N3H6)
  • Additives to cryogenic liquids and solids, such as oxygen and hydrogen
• Methods of modeling, creating, using, and stabilizing these materials for use as rocket propellants are sought

Large Scale Booster Applications

• Reusable Launch Vehicles desire high density propellants to achieve goals of single stage to orbit (SSTO) flight
• Foster innovative ideas for implementing advanced propellants into commercially viable launch vehicles
• Higher energy fuels would be more energetic and more applicable to launch vehicles
• Current materials of interest are:
  • Cubane
  • Strained ring compounds
  • Polymeric Oxygen (O4, O6, O8…)
  • Polymeric Nitrogen (N4, N6, N8…)
  • BH2, BH4, and B-N analogs of prismane (B3N3H6)
  • Additives to cryogenic liquids and solids, such as oxygen and hydrogen
• Higher density propellants, such as gelled hydrogen, or hydrogen with HEDM additives, or other additives, are sought
• Feed system components and ground support equipment development sought

Examples of High Energy Density Materials

HEDM candidates

• Formulated (with exceptions):
  • Polymeric (or Poly) Nitrogen (N4, N6, N8)
  • Polymeric (or Poly) Oxygen (O4, O6, O8)
  • Hydrides of boron (BH2, BH4)
• Theoretical:
  • B-N analogs of Prismane (B3N3H6)
• Reference: Thompson, T., and Rodgers, S., (ed.) �Proceedings of the High Energy Density Matter (HEDM) Contractor Conference held 5-7 June 1994,� PL-TR-94-3036, December 1994.

High Energy Density Materials: Particle Feed Systems

• Analysis shows solid H2 particles with helium (He) fluid carrier is a feasible option for transport of HEDM atoms and materials
• Solid particle feed systems potentially critical to HEDM rocket propulsion
• Particle feed with buoyancy match at cryogenic temperatures is of great interest
• Small feed lines are needed if particles are small – thus, small particles are desired

Title	Author(s)	Source	Topic Area(s)	Year	Link
Atomic Hydrogen Propellants: Historical Perspectives and Future Possibilities	Palaszewski, B.	NASA-Lewis Research Center, AIAA 93-0244, presented at the 31st AIAA Aerospace Science Meeting, Reno, NV	High Energy Density Materials: Particle Feed Systems	1993	NTRS

Conclusions

• Remember the vision for the focused topic
  • Monopropellants for the near term
  • HEDM propellants for future Reusable Launch Vehicles
• Five subtopics planned with these critical technologies
  • Monopropellant fuel development
  • Propellant operations and safety
  • Hypersonic fuel development
  • High energy density propellant formulations
  • Large scale booster applications
• All areas have interest in fuels, propellants, and the methods of creating and using the propellants for commercial space applications
• We look forward to working with you and we invite questions and inquiries for information