Mars Quasi-Direct

So, let’s go to Mars. One of the first – and most important – tasks that I have to accomplish is designing the mission. I’d very much like it to be as accurate as possible, and that means that I have – by myself – to work out the details of how this mission could actually work. Naturally, I don’t need to make it perfect, and there are certain elements that will potentially falter – but as far as possible, I intend to use actual, real-world designs. Elements actually in use today, or at least, on the drawing board. To that end, I’m working on a series of key assumptions – principally, that Falcon Heavy works as advertised, as that’s my favoured launcher for the mission. (I’m going to stress here that this is the first draft of what will likely be several – so most of this is subject to change.)

My basis for this is Mars Direct. I liked the plan when I first read it, twenty years ago, and I like it now, though naturally enough, there are some elements that time has permitted to be updated, and there is one critical modification that I’m opting to make – which I’ll get to in a minute. For those not familiar with the mission plan...I suggest breaking away and consulting Google. At a basis, this plan minimizes the number of launchers needed, and keeps the costs to a minimum. I’m aware that the current NASA Design Reference Mission calls for a more expensive variant called Mars Semi-Direct, but I’m also aware that the original plan to land on the moon was Earth-Orbital Rendezvous, and that the option requiring the development of a far smaller – and cheaper – booster was ultimately taken.

The Falcon Heavy – in the current issued specification – allows for a payload of 16,800kg to be dispatched to Mars. I need two of them for each mission – one for the flight to Mars, and one for the return. The return flight will be dependent on in-situ refuelling. For that matter, the whole mission will be dependent on using local resources, as this flight will last for the better part of three years, almost half of which will be spent on Mars itself. From a purely scientific standpoint, I feel that is essential. There’s no point spending months going to Mars to spend only a few weeks on the surface. An essential precursor mission will have to prove that fuel for the Earth Return Vehicle and water to sustain the crew can be provided. (Which suggests to me that an early sample return mission won’t be Mars samples at all – but distilled water. And if you’re going to do that landing anyway, you might as well do it at your planned base site.)

That gets me to another assumption, and my use of two additional Falcon Heavies. Which will build Mars Base – a pair of Bigelow habitats, solar cells, et cetera. Everything required to sustain a crew on the surface of Mars for ten years. (Yes, ten years – because the goal is for this base to support four or five visiting crews, each of which can build on the work already undertaken.) This technically confines the crews to a single area, but later missions can bring pressurized rovers for extended operations, perhaps a second Falcon Heavy dispatching a pair of them to support the second and subsequent missions.

So, two Falcon Heavy missions per flight. The second one, launched with the crew (though they might elect to transfer across in space, saving some launch weight and allowing an extended check-out period in Earth orbit before the mission actually begins TMI) consists of a ‘Red Dragon’ (again, I know that SpaceX isn’t working on them now, but a lot of work has been done, and it’s the best baseline I can find) a Bigelow Transhab, and all the consumables and equipment needed for the flight to and from Mars. Once the crew enters Mars orbit, they detach from the TransHab, putting it into hibernation for the flight home, and land using the Dragon at the base already present on the ground. Also waiting for them will be the Earth Return Vehicle – another Red Dragon, which will refuel itself on the surface, ready for the crew to ride it to orbit for the trip back to Earth. (Given Mars’ reduced gravity, it will not only carry the crew and the samples gathered during the expedition, but also fuel for the ship itself to return to Earth, the same mix that the landers will use. There’s a back-up possibility as well – if necessary, replacement fuel could be shipped direct from Earth. Though the mission will know that the fuel they require is present before they ever touch down on Mars.

I’m working – at present – on the assumption that the expedition leaves Earth on February 22nd, 2031, arriving at Mars orbit on November 7th. Departure from Mars orbit takes place on February 5th, 2033, with the expedition getting back to Earth orbit on October 20th. As soon as the crew arrive, they’ll be met by a transfer vehicle, presumably a Dragon, to fly them back down to Earth. Optionally, I suppose the ship could dock with a space station instead, but that seems an unnecessary level of complication. To keep the weight down, though, I maintain that the Mars Transfer Vehicle does not need to be able to land on Earth – that’s better accomplished at home.

Which gets me to the second Falcon Heavy. That’s going to be needed for the guts of the Mars Transfer Vehicle – launching the Lander and the Hab is going to take one Falcon Heavy – a second will be required for the engine and the fuel required to get the vehicle too and from Mars. That is conceived as being reusable; refuelled and re-serviced after each mission. (Which actually might require a space station, thinking about it, but only as a ‘Construction Shack’ for the work crew. They could probably use the Hab module, actually, if the work was undertaken shortly after the mission crew arrived back home.

So, the mission plan I’m working on right now calls for four Mars missions using fourteen Falcon Heavy boosters, as well as a few Falcon Nines for other purposes. (There will need to be a satellite network around Mars, for one thing – three combined communication/meterological satellites to support the mission. As well as a few landers at the base site, both to test key systems and to provide reconnaissance of the early exploration area. Most of these missions will launch in the late 2020s, to be ready for the four missions to launch in 2031, 2033, 2035 and 2037. Naturally – there are options to extend to a fifth or a sixth, depending on the condition of the modules. The first two major components launch unmanned on January 3rd, 2029 – the two rockets comprising the first Earth Return Vehicle and the Base components themselves. By September 19th, they’ll be in orbit – and down on the surface shortly thereafter. That gives a year for checking and testing before the first astronauts leave Earth, ready to make history. In late 2030, the two components of the first Martian Transfer Vehicle launch, and are assembled in orbit by the check-out crew before departure. Again – this gives six-plus weeks for systems testing before any commitment to a launch is made.

Looking at the crew, I’m going for a four-man team. While smaller than is perhaps optimal, there is a question of consumables. Water can be recycled, and replenished on Mars itself, but food is a tougher proposition. Four people will, over the duration of the mission, use more than ten tons of food. The base module will carry the food for the first expedition. If a pair of rovers are sent to Mars for the second expedition, then the food for that team might be able to ride-along with that; otherwise, Falcon Nines can provide supply drops, two per expedition, transporting food, medical supplies and new scientific equipment. (Realistically – that would probably happen in any case as a matter of course with each expedition. I’d like to go as pure Mars Direct as possible, and certainly I’m using a lot less than Mars Semi-Direct, but the original plan assumed a considerably larger launcher than the Falcon Heavy, a shuttle-derived Ares V. Theoretically, I suppose SPS might help here, but the Block II design that will unlock its greatest capabilities won’t be available until 2028. At best. I’ve chosen to go with the launch architecture we’ll most likely have. Assuming SpaceX’s new ‘BFR’ doesn’t turn up to invalidate all of this, of course...)

The four-man team will have to multi-task. One will certainly be a doctor – perhaps a flight surgeon, actually, combining the roles of ‘pilot/captain’ and ‘medical officer’ into one astronaut. Yes, I just put Doctor McCoy in charge. The US Navy and Air Force have been training their doctors as fliers for decades; there’s nothing new in this, and the flying will only be critical for a few docking procedures and the landing and launch – all mission-critical, but taking only a few hours out of a three-year mission. It only makes sense to combine the role with another. The second crewmember will be an engineer, likely trained as the backup pilot. The third and fourth comprise the scientific team, and my gut suggests that at least on the first expedition, that means a geologist and a biochemist. That might change for later expeditions, especially based on any discoveries made. (If I had gone with a six-man crew, I’d have included an astronomer/engineer – to make additional use of the transit time – and a geochemist.) It goes without saying that this will be a handpicked crew – probably all of them will have ‘Doctor’, as well as perhaps a military rank.) Of all the elements of this mission plan, this is the one I’m likeliest to stick to.

Having written this, I already know a few things I have to consider again. Nevertheless, this represents my ‘first try’, and gives me a lot of ground to cover in terms of more focused research. The goal, as I said before, is to come up with a mission architecture that would actually work in real life. I don’t want to handwave this, and I want to come up with an expedition profile that could fly. Call it, I don’t know, Mars Quasi-Direct. It’ll do for the moment, anyway.