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Entry System

Mars Microprobe 6 Degree-Of-Freedom
Trajectory Simulation
(quicktime movie 38.5MB... that's really big)

(quicktime movie 2.1MB... a little smaller)

Significant design challenges faced the team working on the Aeroshell System as they aimed for a design which is both simple and cost effective.

Unlike other traditional entry systems like parachutes or rockets, the probes don't separate from their aeroshells. Instead, the aeroshells are carried to the surface where they shatter on impact. The DS2 project is the first to apply a single-stage strategy (from atmospheric entry until impact). This means there are no deployables, parachutes, or airbags to assist in the entry and landing.

Will the probe land like a cat - always on its feet? Yes - the entry system is designed to passively orient itself upon atmospheric entry prior to peak atmospheric heating. Thus, the probes are not required to be spin stabilized on release, nor do they need an active attitude guidance and control system (e.g., thrusters or rockets).

Like a javelin, the probe needs to hit the surface at an appropriate angle or it may never penetrate. So another design challenge for the NASA engineers was to ensure the probe would be properly oriented on impact. This is especially difficult to achieve in the Martian environment, because the probes impact in the transonic flight regime (which is inherently unstable, causing objects to oscillate).

The microprobes are nestled in the nose of the aeroshell to ensure the system's center-of-mass is lower than its center-of-gravity. This helps to ensure the probes always land "right side up", similar to a badminton birdie.

Aeroshell/Entry System

Aeroshell Structure
Flight Aftshell and Heatshield Ready for Final Assembly.

Aeroshell with 
Flight 1 Probe is Installed into the Heatshield.

Aeroshell together
Flight 1 Aeroshell Fully Assembled.


  • Completely passive entry (no rockets for active control)
  • Single-stage to penetration (no parachutes, airbags, separations)
  • Extremely light weight (weighs less than 1.2 kg, or 2.6 lbs)
  • Brittle silicon carbide aeroshell structure (same material used to make sandpaper) which shatters on impact
  • Advanced heatshield material called SIRCA-SPLIT (Silicon-Impregnated Reusable Ceramic Ablator - Secondary Polymer Layer-Impregnated Technique) which is capable of withstanding surface temperatures up to 2000° C (3,632° F) while maintaining the probes internal temperature to within a few degrees of -40 C (-40 F).

Why is it exciting?

  • Mass savings of 50% or more over conventional thermal protection system technologies
  • Tolerant entry conditions simplify deployment
  • Non-erosive material simplifies aerothermal and aerodynamic analysis

Who needs it?

  • Future penetrator missions
  • Any low-cost, passive entry into any planetary atmosphere


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This page last updated: November 24, 1999
For comments and suggestions, or to request
additional information please contact:
Deep Space 2 Outreach and Education
Jet Propulsion Laboratory
4800 Oak Grove Avenue
M/S 301-235
Pasadena, CA 91109