Mars Sample Return: Project Rigel

MarsDrive hosted a competition in 2008 to create an Mars Sample Return (MSR) design that would cost under $2 billion.  Of the five entries, Project Rigel was selected as the winning entry by NASA’s Chris McKay and executive director of The Planetary Society Louis Friedman.  Rigel was designed by Kent Nebergall, who also won a similar Earth Return Competition with The Mars Society in 2004.

MSR, especially with in situ propellant production, involves many nested requirements.  Kent created a massive spreadsheet that calculated these elements and then created twenty different designs based on returned sample mass. By graphing comparisons of these twenty designs against the limitations of the launch vehicle and entry capsule, he found the most feasible design of the twenty and created the vehicle schematics from there. By staying as far away as possible from the limits of the design box, mass creep with future design iterations have a minimal impact on the design itself.

To minimize development costs, Rigel was created with three design rules:

Design Rule 1 – Proven Wherever Possible

First priority is given to vehicle components that have already flown to Mars or would prior to this vehicle being built.  This vastly reduces development time and effort, and also reduces risk since the designs will have been flight tested.  In some cases, elements that were designed but not actually launched may be considered over elements that have not been designed yet.  Examples are listed below.

• The aeroshell is a direct copy of the one for Mars Science Laboratory (MSL), and the vehicle is designed to weigh less than MSL in order to allow for mass creep in future iterations.
• The rover for sample gathering is almost identical to the Spirit/Opportunity rovers currently on Mars. The design has clearly proved more durable than designed, and has exceeded the lifespan required for Mars Sample Return dramatically. Furthermore, many engineering items, such as long term exposure of solar panels, seasonal survivability, and so on – have been characterized for both the rover and the lander by the dramatic lifetime of these rovers.
• Several instruments on the lander for characterizing samples are duplicates of ones flown on MER, Phoenix, and to be flown on ExoMars. In particular, a US-designed ExoMars instrument to detect the handedness of amino acids is included to pre-screen the samples.
• The lander is modeled after Viking, with a truncated triangular design.
• The return sample entry capsule is based on a pair of similar designs from Dr Robert Zubrin and EADS. A similar capsule is to be flown on the Phobos-Grunt mission by the RSA.

Design Rule 2 – If not Proven, Simple

Second priority is given to items that could be inexpensively prototyped.  Whenever possible, when new equipment is designed, it is relentlessly simplified to reduce the probability of mechanical failure and development cost issues. Put simply, if it can’t be prototyped in a garage, find something that can.  This applied mainly to the solar array deployment, but also applied to the sample collection system on the rover, the Earth return capsule, and other elements.

Design Rule 3 – Best of the Rest

These two criteria vastly reduce the development costs associated with the mission.  The return vehicle cruise stage is one of the few systems that does fall directly in either category, and even it was designed with as many components borrowed from other Mars missions as possible.  Ascent stages were designed based on the most recent, advanced studies of these elements that could be found.

Design Corollary: Repeatable

Spin-offs were considered very early in the design process to allow for follow-up missions using as many components of the original mission as possible, or to allow for changes in primary landing site based on future discoveries. Initial sketches of a mid-latitude and polar drill/sample return follow up missions are included.    Follow-up missions can be built using backup parts from the initial mission or an increased production of components as part of a larger program.

The Legacy of Rigel

Rigel became the design inspiration of Mars Workbench (originally called Mars Sample Return Prototype Challenge).  When The Mars Society went through 40 entries for the Mars Project Challenge, it was one of the top ten selected.  In voting, it came in second behind a cubesat project called TEMPO3.

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