Architecture

Red Dragon

“Red Dragon” is a potential variant of the SpaceX Dragon capsule that will be able to land on Mars, currently being investigated by NASA and SpaceX.

The first series of Dragon capsules, including the one that historically became the first commercial spacecraft to dock with the ISS, were designed to splash down in water, like those used in NASA’s Mercury, Gemini and Apollo programs, and like NASA’s new Orion capsule.

The next generation of Dragon capsules, currently in development at SpaceX, are fitted with eight SuperDraco engines. These are a powerful new variation of the Draco engines used by the current Dragon RCS (Reaction Control System). Like the Dracos, they use non-cryogenic propellant (monomethyl hydrazine fuel and nitrogen tetroxide oxidiser), however, they’re much more powerful, each capable of delivering about 67 kilonewtons (15,000lbf) of axial thrust, for a total of about 534kN (120,000lbf). These engines will enable the Dragon to land on solid ground back at the launchpad, saving the time and expense of water recovery, and opening up the possibility for Dragon capsules to land on Mars. This is in alignment with SpaceX CEO Elon Musk’s stated purpose of establishing settlements on Mars.

Red Dragon will presumably be based on this or a similar engine configuration, with modifications to suit EDL on Mars. Variations may include:

  • Remove systems unique to LEO missions, such as berthing hardware.
  • Add deep space communications.
  • Modifications to SuperDraco engines to suit Martian atmosphere.
  • Reduction of heat shield mass.
  • Algorithms/avionics to enable pinpoint landing on Mars.

The gravity on Mars is lower, which reduces the acceleration of the capsule towards Mars; however, the capsule will be approaching from interplanetary space at a much higher velocity than if it were approaching from Earth orbit. Also, Mars’ atmosphere is much thinner (less than 1%) than Earth’s, so it will play less of a role in reducing spacecraft velocity during EDL. However, for the same reason, there is less heating due to atmospheric friction, and therefore less (or different) heat shield material may potentially be used. The different conditions will affect the forces experienced by the spacecraft, which may necessitate changes to thrusters, heat shield, avionics and other factors.

Red Dragon landing on Mars
Red Dragon landing on Mars

Another clear advantage is that a landed capsule can be repurposed as a storage unit, shelter or habitat.

Once the Red Dragon technology has been proven as a reliable mechanism for delivery of cargo, this approach may be used to deliver up to seven crew to Mars surface, by using a DragonRider modified in the same way.

Red Dragon represents a near term technology that can enable comparatively inexpensive and functional Mars missions. It’s an fundamental element of the Blue Dragon architecture, being utilised for both crew and cargo delivery to Mars surface.

Theoretically, Red Dragon will be able to land with a high degree of accuracy. From the SpaceX website:

SuperDraco engines will power a revolutionary launch escape system that will make Dragon the safest spacecraft in history and enable it to land propulsively on Earth or another planet with pinpoint accuracy.

This ability to land “with pinpoint accuracy” is supported by the Dragon Guidance, Navigation and Control (GNC) system. Due to the lack of GPS on Mars, alternate methods of achieving high-accuracy landings must be achieved using alternate methods; however, this problem is effectively solved. For example, Jeff Delaune at ESA has been developing a system known as “LION” (Landing with Inertial and Optical Navigation) that enables pinpoint landing on the Moon, Mars and asteroids using image recognition of major landmarks. Another impressive development is the Fuel Optimal Large Divert Guidance (G-FOLD) algorithm developed by JPL, able to autonomously calculate landing trajectories in real-time. This was recently tested with Masten Space System’s Xombie VTOL experimental rocket, very successfully, making a 750 metre course correction in real time. Considering these developments it’s safe to assume that the Red Dragon will be capable of pinpoint landings on Mars by the time we begin sending them, enabling a neat and optimised layout of the base to be designed beforehand.

It’s estimated that a payload of up to ~2 tonnes can be delivered to Mars surface via a Red Dragon. This will be a major breakthrough in the goal of human settlement of Mars.

Red Dragon potentially represents a mechanism for delivering cargo to the surface of Mars that is not only repeatable, but affordable. SpaceX currently charge $135M for a Falcon Heavy launch including the Dragon capsule. Making use of COTS and other pre-developed hardware, and simplifying missions, it may be possible to design and build a payload and send it to Mars for only $200 – $250M. Compare this with the $2.5B price tag of the Curiosity rover.

Once SpaceX have developed their RLS for the Falcon Heavy – a goal likely to be achieved within a few years, in light of the recent Grasshopper tests, and thus well before the first H2M mission – this price will come down even further.

Red SuperDragons

The architecture for the Mars One mission, which proposes to send up to 40 astronauts on a one-way mission to Mars, relies on a larger, 5-metre-diameter Dragon capsule for habitat modules. Although these are yet be to be built or demonstrated, their plan is to land the first two of these on Mars in 2020 – only 7 years from the time of writing.

Mars One settlement
Mars One settlement

Therefore, it can be inferred that a plan exists to have operational “SuperDragons” available within 7 years. This is well within the timeline of Blue Dragon.

Mars One is also planning to build a model settlement in a Mars analog environment in order to commence crew training in 2015, so it may even be possible that we will see what the SuperDragon capsules look like within 2 years or less.

At present the Blue Dragon architecture does not incorporate SuperDragon capsules. However, this may change as more information about them becomes available.

 

Ice Dragon

NASA have commenced studies of a mission to Mars based on the Red Dragon landing system, which may be flown as early as 2018. Known as “Ice Dragon”, it’s being developed in collaboration with SpaceX, and will deliver a science package to Mars including a drill that will penetrate up to two metres into the permafrost to investigate environmental conditions suitable for past or extant life.

There are 6 objectives currently envisaged for Ice Dragon[xx]:

  1. Determine if life ever arose on Mars.
  2. Assess subsurface habitability.
  3. Establish the origin, vertical distribution and composition of ground ice.
  4. Assess potential human hazards in dust, regolith and ground ice, and cosmic radiation.
  5. Demonstrate ISRU for propellant production on Mars.
  6. Conduct human relevant EDL demonstration.

Aside from the scientific outcomes of the mission, perhaps the most important contribution of Ice Dragon will be the demonstration of the EDL capabilities of the Red Dragon capsule.