Thursday, October 20, 2016

Reddit is distracting

Low post rate here lately has been because I've gotten sucked into reddit's r/spacex forum.

Partly for my own reference, here are links to some comments and submissions I've made:

Single-window round trip of the ITS ship
This was a trial run using Trajectory Optimization Tool to see if it was possible to send an ITS ship to Mars and return it within the same window. Provided you can refuel the ship in about a week and can handle a long (>200 days) return trip, it's definitely possible.

ITS system performance tables for near-Earth space
(public spreadsheet supporting tables)
A table of payload performance values for missions to various locations around the Earth and the Moon, with estimated costs.

ISRU system scaled to fuel one ITS ship per window, pt1
An extrapolation from an ISRU study that outlines the equipment needed to refuel an ITS ship (1950 tons of propellant) in one synod (~780 days). Includes mass estimates and is based on fairly good data. TL;DR is about 101 tons of gear and 20 tons of spares, with another 10-20 tons of spares each trip. The ISRU advantage is 16:1 for the first trip and about 98:1 for the next four trips. If the replacement cost is amortized over ten years then the advantage is 48.5 tons of propellant per ton of equipment.

Discussion of radiation shielding
This is an extension of my thoughts on shielding for large, permanent habitats that require Earthlike radiation levels. The conclusions do not apply for spacecraft in general because most spacecraft proposals cannot support several tons of shielding per square meter of surface area.