The FISO presentation from May has been released. I’ll definitely use this in the project, to show how it could be improved by dumping SLS/Orion.
[Update a while later]
OK, I’ve glanced through it. There isn’t much in the way of numbers (Isp, mass, etc.) to make it easy to come up with alternatives. I will note that they are looking at 17 or eighteen SLS flights over a two-decade period, or about once a year. That probably implies a couple billion per flight, ignoring all the money we’re currently wasting on development.
It looks like “Mars Long Stay Crew” 2021-2033 represents $130B in 2014 dollars. (This is using fingers to measure its portion year by year of the inflation adjusted budget which is a bit fantastic since the figure busts the budget if added to current programs.) Adding Phobos crew, “current programs” and so on gives a more grim figure to attribute to the cost of getting NASA astronauts to Mars of NASA’s entire budget for the entire period 2015-2033: $342B in 2014 dollars–this is just integrating below the dashed line, not $100B or so over the line.
First, planning out missions which span five or more presidential elections, and counting on NASA’s budget keeping pace with inflation over that time period, is sheer folly. In just four years from now, half the Baby Boomers will have turned 65. People who were teenagers during Apollo will become senior citizens during the next administration.
I’d say if you’re looking to get a manned Mars mission done through NASA, then you’ve got to use NASA’s current budget without adjustment for inflation as a best case scenario.
Next, the FISO launch schedule repeatedly shows several elements launched together on one SLS. In particular, it shows a couple identical 100kW solar electric tugs. There is no reason why these separate modules need to be all launched together. If launched separately, then vehicle choice expands well beyond the SLS. The largest mass mentioned in the PDF is 30 tons, well within the range of several currently used rocket families.
Much of the mass being launched is of course propellant. Having a propellant depot in LEO would allow the various components of Mars and other missions to be launched dry. As long as the interface is defined between launch vehicles and the propellant depot, it doesn’t matter who launches Xenon or LOX nor in what quantity. Launching a solar electric tug empty gives a 16 ton advantage, meaning a whole class of medium launchers could do the job.
I think they have glossed over the whole step of the 9 month journey from high Earth orbit to high Mars orbit. They expect 4 astronauts to spend 250 days in Orion and a Deep Space Hab, which looks to be maybe 2 or 3 times the volume of Orion. I think your transfer vessel is going to look a lot more like NAUTILUS-X.
And if you look at NAUTILUS-X, there is only one component which would need the capacity of SLS. Most of the rest of it is Bigelow modules and an inflatable torus (which would also probably come from Bigelow).
So, if one is to take anything from the FISO presentation, it should be the modular, reusable elements – the solar electric tugs, the refuelable chemical transfer stages – and begin to deploy them for missions within the next few years. Re-use them over and over again in cislunar space.
Start with a propellant depot in low Earth orbit, and use these tugs and chemical transfer stages to establish a depot in lunar orbit. The solar tugs can transport materiel to lunar orbit, the chemical stages can be used to send stuff to the surface of the moon and back to orbit. Whomever owns depots should pay some price for delivery of propellant to the depot and charge some slightly higher amount to anyone who wants propellant from them.
Then it doesn’t matter who delivers Xenon to LEO, nor how much. They just get paid X $/kg by the depot owner, who then sells it for (X+Y) $/kg to its customers. Any launch company capable of delivering Xenon in any quantity to LEO gets a chance at market share – same goes for any other propellants stored at the depot. And with these reusable chemical or solar-electric tugs flitting about cislunar space, design bugs will get hammered out in the course of doing useful work long before they are pressed into service on Mars.
And if the Mars transfer stage is more like NAUTILUS-X, then this stage and the deep space habitats wouldn’t need to be purpose-built for a Mars mission. Elements of the vehicle such as inflatable hab modules and agriponics and so on would be tested through their use in cislunar space just in the regular course of the Bigelow business plan. In fact, some of the modules eventually sent to Mars would already have seen use in other applications in low earth orbit or elsewhere in cislunar space.
This also works with the satellite servicing idea mentioned in another thread, as well as ULA’s integrated vehicle fluids idea. Much of what Jon Goff et al. are doing at Altius with the robotic arms and 3D scanning for the asteroid retrieval mission could also be applied to a servicing satellite.
Ideally, we’d have so much going on in cislunar space with the depots, getting a lunar base going at the poles and whatnot, that we’d just end up already having most of what we need for the Phobos mission already in orbit.