Monday, September 28, 2015

Early days - space nuclear reactor program costs (3/4)

third of four.

Space Nuclear Power Program

This program aims to develop high-power, safe, reliable nuclear energy sources for manned and deep-space missions. Nuclear electric propulsion will open a new frontier of exploration in the outer solar system and allow manned missions to Mars and other places with difficult solar power problems.

A starting point might be the direct gas reactor studied for the Prometheus project, a 1MWt/200kWe reactor at 40-50kg/kW (7.5-11t). Another might be the heatpipe reactor SAFE-400, a 400kWt/100kWe reactor at unknown specific mass. Sodium-cooled designs in the 70kg/kW range are also possible. (Masses include radiators, conversion and power conditioning.)
The SAFE-30 project demonstrated simple, affordable ground testing of non-nuclear components. The Prometheus project demonstrated productive cooperation with Naval Reactors and related organizations to tap their nuclear technology expertise. Joining these approaches will allow the project to proceed immediately into materials testing and design optimization. The most urgently needed component is an experimental fast reactor for materials testing. Also critical will be a design process that focuses on modular power units so the same basic design can be used for a wide range of missions, presumably in the 50-100kWe range.
Costs are not straightforward to estimate. One baseline figure is the $4.2 billion estimated to develop the Prometheus reactor system. Let’s assume a 50% increase on that figure and use $6.3 billion for the development program; further assume hardware costs of $5000 per watt. Three demonstration units will be built: one for flight test (possibly on a later carrier flight), one for a NEP asteroid capture and one as a base power supply for a manned mission. The goal is a 50kWe power unit massing 2,000kg or better (40kg/kW) with at least 20-year useful life. Individual units could power NEP asteroid retrieval tugs or small ISRU operations; sets of four could power manned bases or deep-space probes. A second phase using knowledge gained from the first generation reactor program would aim to build power units of 1MWe and 10t mass range (~10kg/kW) for use on deep-space and interstellar probes, permanent bases and orbital manufacturing facilities. All future NEP missions would be able to use a proven, existing design and avoid developmental uncertainties.
Estimated costs:
$6,300m development program
$750m flight hardware
$2,115m margin
$9,165m total cost ($611m per year)
Alternate scenario: A fast-spectrum reactor is made available by another country or organization for materials testing. Majority of the design, testing and construction is outsourced to Naval Reactors and experienced contractors. Additional funding is provided by ESA and allied space agencies in return for access to flight hardware. Development program costs cut in half and a fourth power unit is built for ESA use. New costs: $3,150, $750, $1,170, total cost $5,070 ($338m per year).

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