The Mars Surface Habitat, or, more simply, “the hab”, is a custom-built piece of hardware designed to accommodate, ideally, a crew of 6 astronauts on the surface of Mars. It must therefore include cabins, common areas (kitchen/dining), laboratories and other work areas, ECLSS (Environment Control and Life Support Systems), waste-disposal, heating, lighting, cooking and electrical systems.
The current intention is for the hab to also include ISRU (In Situ Resource Utilisation) equipment capable of extracting water, oxygen and nitrogen from the Martian atmosphere. These will be used to maintain water and air supplies for the crew, compensating for losses due to leakage, inefficiencies in recycling systems, airlock usage, and possibly other factors. It will therefore also include appropriate tanks to store sufficient quantities of these fluids.
The hab may include inflatable modules. If possible, these will be inflated using oxygen and nitrogen obtained from the Martian atmosphere during the 26 months between arrival of the hab and arrival of Alpha Crew.
Unlike Mars Direct, DRA5 or the Mars-Oz architecture, in Blue Dragon the hab is landed uncrewed for reasons of improved safety. It is to be sent to Mars at approximately the same time as the MAV (Mars Ascent Vehicle) and landed nearby.
On arrival at Mars surface:
- The power system (solar and/or nuclear) will be activated.
- Doors containing inflatable modules will open.
- The ISRU unit will be activated and harvesting of O2, N2 and H2O (oxygen, nitrogen and water) from the atmo will commence.
- The inflatable modules will inflate while the water tanks fill.
- Once the hab is inflated, the O2 and N2 tanks will also fill.
A completely uneducated guess at the cost of development of the hab will be around $2-5 billion. This is based on comparison with MSL (Mars Science Laboratory, also known as Curiosity), which, so far, has cost an estimated $2.5B. While the hab is more complex than Curiosity in certain important ways (e.g. it must keep people alive), it is simpler in others (e.g. it doesn’t have to move). Furthermore, the intention is for private contractors to develop and manufacture the hab, rather than a large agency such as NASA, which should, in theory, significantly reduce costs.
For the basic form of the hab, previous architectures such as Mars Direct and DRA5 have primarily focused on a vertical cylinder; the so-called “tuna can” model:
This form of habitat is usually assumed to have a diameter of around 8 metres, which will fit inside the fairing of an SLS (Space Launch System) heavy lift rocket.
However, this vehicle is yet to be developed, and I would prefer that this architecture be independent of NASA-built rockets. You may well ask: Why? The answer is one word: Ares.
A very brief history lesson:
After the Vision for Space Exploration was announced in 2004, NASA began a new program of hardware development called the Constellation Program, which included two new rockets: Ares I and Ares V. Ares V was designed as a HLLV (Heavy Lift Launch Vehicle) with a 10m diameter – perfect for a tuna can-style Mars hab.
Unfortunately, despite a faked Ares I demonstration, development of the Ares rockets was shelved. A new family of rocket vehicles called the Space Launch System is now being developed instead. The diameter of the SLS fairing will be 8.4 metres, which, again, would be suitable for a tuna can Mars hab.
However, in light of what happened with the Ares vehicles, the fact that NASA pulled out of ExoMars due to cost overruns elsewhere, and because of the budget sequestration currently being implemented in the US, I feel that it would be a mistake to believe that the SLS will definitely be built. Of course, I hope it will, because we really need heavy lift capability and that nice, wide payload fairing. I just don’t want to rely on it. SLS could be cancelled just as easily as Ares was by the next administration.
There is hope for heavy lift. SpaceX is apparently planning to develop a super-heavy lift vehicle called the Falcon X, which will also have a fairing diameter of about 8m. Based on their track record, I believe SpaceX will achieve this goal. However, it could be years away, and if we say we definitely need that rocket then it’s back to the waiting game.
The real question is – do we actually definitely need it? Do we really want to wait around until someone builds a rocket with a big enough fairing? Or can we make do with what we have?
For now I’ll continue to assume we’ll have access to the Falcon Heavy in the near future, especially since I’ve seen one under construction at SpaceX. The dimensions of the the Falcon Heavy fairing are the same as the Falcon 9, as follows:
As you can see, there is only a 4.6m diameter available.
It would be hard to imagine a good vertical cylinder hab configuration with such a narrow diameter, even if you designed it to be the full height of this fairing. Perhaps it could be done. Respectable individuals such as Robert Zubrin have already looked at doing H2M (Humans to Mars) with just a Dragon capsule, which obviously fits in this fairing. It would be smaller than a Tokyo apartment, and the mission would probably require the crew size to be reduced to two, but, theoretically it could be done.
Is there another way? Jonathan Clarke and David Willson from Mars Society Australia have studied horizontal Mars habitats based on a bent biconic design:
This habitat is 18 metres long, with a diameter of 4.78 metres, which will almost fit inside a Falcon Heavy fairing. It’s designed to accommodate a crew of 4. This approach offers several advantages other than dimensions and orientation, which are discussed in the paper A Practical Architecture for Exploration-Focused Manned Mars Missions Using Chemical Propulsion, Solar Power Generation and In-Situ Resource Utilisation by Willson and Clarke:
- The biconic shape has a better lift-to-drag ratio than the traditional vertical cylinder, and is therefore easier and safer to land (especially important if people are in it).
- It can be lengthened by attaching additional sections, delivered separately.
- It permits longer cargo length (such as a rover).
- The loading ramp has a lower gradient, which is safer.
- It’s much easier to tow a shape like this into a good location. Vertical cylinders must stay where they land.
The above design will not fit within a SpaceX Falcon Heavy fairing. It’s a bit wide, much too long, and the bent biconic shape wouldn’t fit into the fairing. But perhaps we can use it as inspiration for one that will fit:
In this sketch the hab is shown fitting as snugly as possible within the fairing, implying that thrusters, legs, EDL (Entry, Descent and Landing) hardware, etc., are set into the hab shape. The blue lines show the floor and ceiling of the liveable volume – the sections above and below that would be for equipment and storage.
This volume is probably still slightly small if we decide to stick to our desired crew size of 6. There are a couple of things we can do:
- We can reduce the crew size.
- We can send a few of these to Mars, and possibly connect them up.
- We can add inflatable modules.
This third idea has recently been developed by Polish engineer Dr. Janek Kozicki, whose design concept is based on the 8m diameter hab described in the DRA5, designed to fit within the payload fairing of the SLS:
As you can see, the addition of 3 inflatable modules to the central hab significantly adds to the total pressurised volume. This is an innovative solution with considerable value, especially when you consider that each Falcon Heavy launch costs $128M. This way we may be able to keep our preferred crew size of six.
The most obvious downside of using inflatable modules is that they provide less protection from harmful radiation. Whereas you could pile sandbags on top of the solid metal hab, that may not be practical with the inflatable modules. But this problem is probably solvable.
The next question is, can we adapt this concept to a horizontal cylinder? Well, of course. Here’s a thoroughly amateur Photoshop drawing to illustrate:
After landing, the hab is remotely activated from Earth, causing the inflatable section of the habitat to inflate. This is perhaps most easily achieved using compressed air. However, a far more interesting option is to manufacture the air from local resources (ISRU) and inflate the hab gradually. Since we are sending the hab one launch window earlier than the crew, we will have about 26 months in which to inflate the hab and test its various systems.
More research needs to be done into the nature of the air-making unit, which would harvest oxygen and nitrogen from the Martian atmosphere. We need to know if we can make enough air in the time available, how much the unit will weigh, and its energy requirements.
If we can develop a realistic and affordable hab around this concept, it means we’re one step closer to Mars – without having to wait for SLS or Falcon X.
There’s still one very important thing to consider, though: mass.