Paul March looked at approaches for developing a Space Launcher Infrastructure that can provide for safe & rapid transport of up to 25 people to LEO AND provide low cost transport of bulk cargo to LEO for less than $100 per pound. (68 pages)
NOTE – Selenian Boondocks – Kirk Sorenson has written why he thinks single stage to orbit nuclear thermal rockets are a bad idea. With current materials and designs the thrust weight ratios are too low.
Paul March presented and discussed the possibilities of using Nuclear Energy in A Single Stage To Orbit (SSTO) Cargo only Launcher System.
To lower costs for space access –
We need to increase the flight rate and technologies.
1) Add small one or two stage fully reusable vehicles optimized for putting ~25 people into orbit.
2) Add LARGE UNMANNED fully reusable cargo lifters that can drive the cost per pound below $100 per pound with the appropriate flight rate.
For the Nuclear approach, we should utilize a fully reusable SSTO, Vertical Take Off and Landing (VTOL), Lox Augmented-Nuclear Thermal Rocket (LA-NTR) launch system.
Air Force Test Bed Timber-Wind NTR (Nuclear Thermal Rocket) (1992) T/W (Thrust/Weight)= 25:1
Proposed Particle Bed-NASA Glenn LA-NTR T/W could be NTR=25:1 & LA-NTR=75:1 or better.
For a 750,000 lbs-f LA-NTR 4:1-O/F engine, that implies that engine mass could be as low as 10,000 lbs!
To be conservative, lets assume 20,000 lbs per engine including shielding for this analysis. That provides a T/W of 38:1 and is only 2,000 lbs heaver than the Saturn-V
first stage engine, the F1, which had a dry mass of 18,000 lbs and a Sea Level (SL) thrust of 1,522,000 lbs-f @ Isp = 265 sec.
Estimated Development time for LA-NTR engine: ~Ten (10) years but could be shortened if funded right.
To obtain high T/W ratios, LOX Augmentation must be used.
Other Possible Nuclear fuel Cycles
* Thin-film Fragment-Fission approach based on Am-242radioisotope.
* Fission based gaseous Light-Bulb approach using gaseous U-235 Hexafluoride nuclear fuel
* Aneutronic Fusion Based Fuel Cycle based on hydrogen and boron
LA NTR design choices
* LANTR Segmented Aerospike Nozzle with variable thrust control on each LANTR engine for attitude and trajectory control. No gimballing.
* Canard Stabilator Flight ControlSurfaces + H2O-ResistojetReaction Control System (RCS)
* Fail-Op Landing Strutsto perform multiple functions including Support, Aerodynamic Control, Heat Rejection & landing shock absorption. Required: 5
* X-33Metallic Reentry Thermal Protection System on “bottom” of ship plus Carbon-Carbon leading edges on all Landing Struts and Stabilators.
* Graphite-Aluminum low neutron absorption structural material will be used in and around LANTR engine compartment.
* Cargo Bayt o be similar to Shuttle’s except wider (~33 feet wide by 60-to-90 feet long).Utilize Saturn-V Tank Diameter (33’) for building liquid hydrogen and oxygen tanks. This implies an H2tank length of 175’ and O2tank length of ~20’.
& Boron-10 Neutron Shields will be provided for ground and space flight crews. Shields will provide 5-Rem per year exposure rates for all manned operations around the vehicle including manned EVAs.
* LANTR to use Los Alamos Dumbo, USAF Timber-Wind Particle Bed(PB),or Russian Zr-hydride Heterogeneous design with ternary-carbide fuels at power densities in the 20-to-40 Megawatt/liter range. (Implies ~3,000K chamber temperature.)
* Hydrogen, LOX and Waterpumps to be electrically or hot hydrogen driven.
* All Electric powercomes from five (5) helium-xenon cooled ~5.0 MegawattBrayton Cycle turbo-alternators. (Assume 1.0 kg/kWe & 30% Cycle Eff.)
* Landing struts do triple-duty. Landing gear with Shock Absorbers, heat radiator for turbo-alternators and LANTR reactors plus provide control surfaces.
* Neutron Shields to be graphite-aluminum walled tanks filled with H2O loaded with boron-10.
* Integrated Brayton-Cycle heat exchangers in the LA-NTR reactor core used for turbo-alternators.