The old Delta Clipper concept was a very cool outcome from the old SDIO, but NASA and its cronies killed it, either through false promises of “something better” (remember “VentureStar”?) or neglect. However not everyone has forgotten DC-X’s potential and Eric Davies has even proposed an upgrade to nuclear…
… not a pure NTR but an LOX Augmented NTR (LANTR) to have sufficient thrust-to-mass to get into orbit. According to the sources behind the original study (a 2004 review by Eric Davis) NTRs have been operated without any radionuclides entering the exhaust stream, so it should be “safe” within the atmosphere. Aside from prompt X-ray and neutron radiation from an operating reactor, that is, neither of which is lasting. We surround launching chemical rockets with a necessary danger zone and an NTR would be no different. Probably not even significantly larger either since the thing wouldn’t explode as mightily as an Ares V or a Shuttle in the worst case scenario. Plus a reactor core designed to run at 3000 K and 100 ATM is going to be a tough mofo to start with.
The proposed NTR is a centrifuged particle bed reactor, based on the “Timberwind” system studied by the SDIO. That, of course, made the Greens and NoNukers shit kittens when originally proposed, but I suspect the political mood is more receptive now to nuke-power than it has ever been, especially if people see more civilian action and more noises about nuclear disarmament. Lobbing Solar Power Satellite components to orbit 100 tons at a time should make an LANTR attractive to any right thinking Green – like yours truly – because the overall fossil fuel cost is reduced significantly.
Once enough installed beamed-power is available to launch Leik Myrabo’s Lightships then the LANTR can be moved permanently off-world, where it really should be. But until then it’s one solution we should examine while trying to reduce the cost to LEO.
Hat-tip to Brian Wang for spotting this one… Nuclear DC-X