AAE 450- ERV Propulsion

1. AAE 450- ERV Propulsion Stephen Hanna Preliminary Design Analysis 1/23/01

2. Outline (no show) • Definitions/ Mission • Design Philosophy/Strategies • Requirements/ Goals/Limitations • Options • Launch Vehicles Available • ERV launch • Technology • ERV in transit • Technology/ attitude control/ etc • Conclusion • Further study • Questions Comments • ‘No Show’ slides due to time constraints will not be presented • Any Questions about ‘No Show’ slides should be asked after presentation is complete ‘Time Permitting’

3. Define Mission (no show) • Cost • Lift payload of ~75 tonnes to LEO • ~50% of Cost of space systems is propulsion. • Propulsion costs are derived from WEIGHT • Safety • Proven technology • Mission Success • Based on combination of Cost and Safety

4. Design Philosophy: Un- Manned Rating (no show) • Simple designs should be used to full extent • Redundancy crucial in all critical systems, where practical. (critical meaning failure to function causes irreparable mission failure) • High- quality, tests of actual system hardware/software should be a primary requirement

5. Design Philosophy: Man Rating (no show) • Simple designs should be used to full extent • Redundancy crucial in all critical systems, where practical. (critical meaning failure to function causes loss of life) • High- quality, unmanned tests of actual system hardware/software should be a primary requirement • Safety decisions should not be influenced by cost, manpower, or schedule. Risk assessments should be preformed to determine impact of these factors on the system.

6. Design Philosophy:Minimum Risk (no show) • Critical systems and components where redundancy is not practical (I.e. structures, pressure vessels, fittings, etc.) shall be designed for min risk using conservative design specifications (factors of safety, positive life margins, leak before burst , etc.).

7. Strategies • A heavy lift launch vehicle to limit on- orbit assembly • A split mission strategy (cargo and crew fly on separate missions) • Pre-deployed and verified “turn- key” habitats with ‘in situ’ capabilities

8. Requirements/Limitations • Launch a Earth Return Vehicle (~2011) with “in sitiu” propellant production plant and all necessary supplies (rover, scientific equipment, food, etc..) • Approximate payload weight for preliminary design ~75 tonnes • Payload weight estimated using DRM (~100 tons) and Zub. (~45 tons) as boundaries • Does not include upper stage weights ~100 tonnes and ~95 tonnes, DRM and Zub., respectively • Preliminary DV for launch from earth ~7.6 km/s and DV of ~3.7 km/s to get to MARS • From Team B Orbits Group initial estimates • Plus an additional 20% Delta V for gravity and aerodynamic losses • Plus an additional 5% Delta V for Orbit adjustments due time delays • Approximate payload dimensions similar to DRM and Zub.’s

9. Requirements/Limitations • Use existing launch vehicle technology (modified) • Why? Cost of Building a “Large Heavy Lifting Vehicle” is in BILLIONS of dollars for desired safety factor • Generic H.L.V. for both HAB and ERV is viable • Final stage of rocket can be modified for specific payload weight and to use the “no human factors” plus of the ERV • Nuclear Thermal Rocket for final stage • Best weight to thrust • Estimated Cost ~$1 billion dollars • Attitude Control that is reliable/ robust

10. Launch Vehicles Available(no show) • ALS- NLS • US Heavy launch Vehicle program • approximate cost to continue development ~$12 billion (1992 dollars) not including infrastructure and timeline requirements • Saturn V • US Heavy launch vehicle (not viable, development estimates over ~$15 billion) • Derivatives • Shuttle SRMB and main engine combination • Proven technology, unknown costs for heavy modification • Eneriga Class of Rockets • Russian, Heavy Launch Vehicle • Viable option (Built and on the Shelf)

11. ERV launch(from earth) ]Best Viable Option: [In conjunction with HAB team requirements] Russian Eneriga Class of rockets chosen • Advantages • System all ready tested and production facilities and infrastructure present • To Reduce the cost of development • Use existing Vehicle, with modifications as needed • To reduce the cost of installation of infrastructure • Use existing vehicle with infrastructure present • Modular Design • World Collaboration spread risk • Bonus: Rubble, more bang for your buck • Disadvantages • US companies do not profit; No longer a patriotic mission • Might delay timeliness of launch, Russian Pictures from http://www.friendspartners.org/~mwade/lvsenergia.htm

12. Nuclear Thermal Rocket: Existing Derived Technology for Upper Stage Three most researched/ funded NTR’s to date: • NERVA (Nuclear Engine for Rocket Vehicle Technology) • Flight engine developed in 1970’s • Lowest Performance NTR in ISP terms • Most Money invested • Similar Program  CIS (commonwealth of independent states) technology is similar but less infrastructure and testing available • PBR (Particle Bed Technology) • Highest Performance NTR in ISP terms for solid core design (high safety factors) • Similar Program  PBR is NERVA derived and has some technology crossover that can be applied to NERVA • Project Conclusion in 1993 • CERMET – Core nuclear rocket • Good design if reusability an issue, cannot meet timeline requirements in a costly manner

13. NTR (NERVA derived): Record (no show) • Largest Endeavor for NTR research over twenty years research with the most money appropriated (1947 USAF Start,1958 NASA runs, & Fin.1972). • All research available and infrastructure still present for program to be reactivated • Flight model complete before project completion and was tested • 28 full power tests with restarts • Restart time from 1hr to 1 year • Life span of three years • Up to 30- minute test durations • Most time tested on engines 4.5 hrs total • Reactor sizes ranging from 300 Mw to 200,000Mw • Development of way to contain affluent (propellant exhaust gases) for safe ground testing (used on later tests) • Development of various high temperature fuels • Solution to problem of fuel erosion of Hot- Hydrogen

14. NTR (NERVA derived): Record cont… (no show) • Specific Impulse as high as 835 sec (avg. 825) • Recent studies point to improvements saying ISP levels of ~1000 sec • Thrust levels as high as 890,000 N • Recent studies sight major possible improvements • “dual mode”- can be used for onboard electric power and refrigeration • Production tested of up to 100Mw • Proven Ground Technology • Excellent safety record

15. NTR (NERVA derived)- Reactor Safety(no show) • Neutron poisoning for ground handling • Control reflectors and internal safety rods • Primary and auxiliary coolant loop to ensure nuclear heat removal • Emergency mode on the order of 30,000 lb- thrust, 500 sec specific impulse, and 10^8 lb-sec total impulse • Assured shutdown at end of life

16. ERV- NTR(to Mars) Preliminary Design • Propellant Chemistry • NERVA restricted with 70’s technology to 2361K and rods are at 2650K • Note: A thermal gradient from periphery of the coolant channel wall (I.e. increasing coolant (propellant) temperature rises resulting in perphial core temperature increase, melt down) • Gas properties looked at • Hydrogen (H2) 2.016 grams/mole • Methane (CH4) 16.043 grams/mole • Carbon Dioxide (CO2)  44.01 grams/mole • Using this isentropic parameter (g) and Cp(T)  C* can be found • Results need further interpretation

17. ERV- NTR(to Mars) • Trade studies in nozzle's expansion ratio to find ISP (iterative process) • Thermo chemistry- g, M, Tc • Approximate Pc, Pa, and l • Pe is typically varied to find ideal • Evaluate Me (Mach Numb at Exit) • Evaluate expansion ratio • Evaluate Isp and verify l

18. ERV- NTR(to Mars) • Size overall systemusing Rocket Equation • Inert- Mass fraction • Heavier than liquid rockets but have a better thrust to weight ratio. • Most systems similar to liquid engines except for radiation shielding, can double weight of the NTR • If Hydrogen used on the order of 0.5 to 0.7 using NERVA research assumed due to lack of extensive database can be used for initial studies and iterated back to at a later date • Rocket Equation: Delta V = g*ISP*log(Mo/Mf) – Int(Drag/M, tb..0)- g*tb • Propellant Flow Rate: • M(dot)= F/ Isp*g

19. ERV- NTR(to Mars) • Propellant Heating Requirements (important mile marker) • From ISP and desired Thrust- mass flow rate can be found giving us heat needed • Heat is directly proportional for the power required by the reactor Pcore=M(dot)*{Hv+int(Cp dt, t2..t1)}= M(dot)*P [Watts] Example: 1kg/s flow of H2* P=0.018061, T1= 2000K, and T2=3500k {note a linear correlation} **Assuming gas is initially a liquid • Pressure drops • 20-30% pressure loss in regenerative cooling, also for making prop a gas • Core pressure drops show ~30% but improvements taught ~10%

20. ERV in Transit (to Mars) Attitude Control • Primary System: Cold Thrusters from NTR are possible • Secondary system using MMH and N204 possible (used by STS) • Further Study Needed

21. Conclusion (no show) H.L.V. use present technology, Energia Class, with modification of final stage as a NTR propulsion scheme based on NERVA technology

22. Further Study • Finalize Code to size NERVA derived technology based on D V • Thrust Chamber Sys.- Nozzle, Reactor Containment Vessel, Hardware for Cooling and Feed System50%mass • Propellant Storage System 10%margin of safety • Pressurant System isentropic blowdown system • Radiation Shield shield radius equivalent to core radius • Support Structure 10% of total structure • More information on NTR use on Mars as a power source and for return trip using NTR and super heated CH4 • More in depth look at micro thrusters for ERV attitude control • More Cost/ Safety analysis

23. Pertinent Skills Propulsion A&AE 439 A&AE 590K A&AE 590C Aerodynamics A&AE 415 – CMARC, Aero CAD A&AE 412 – CFD Other Surf CAM (can use *.dxf flies with minor editing) CNC machine Question or Comments?

24. References (no show) INCOMPLETE LIST • Buden, D. (EG and G energy Measurements, INC.), Tutorial on Nuclear Thermal Propulsion Safety on Mars, AIAA Paper 92-3696, 1992. • Sanders, Jerry B. (NASA Johnson Space Center), Manned Space Nuclear Systems Design Guidelines, AIAA Paper 92-3418, 1992. • Sivers, R. K. ,Livingstion, J.M. and Pierce, B.L. (Westinghouse Electric Corp.), NERVA propulsion system design considerations, AIAA Paper 90-1951, 1992.