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The Soviet Mars 2 and Mars 3 lander missions were the first (human-made) spacecraft to reach the surface of Mars with Mars 3 the first successful landing. They both carried Prop-M's; the first wheel-less rovers.

A comment below Has any spacecraft attempted to land on Mars without an ablative-type heat shield? references the NASA web page Mars 2 Lander 1971-045D which includes the following description:

Spacecraft and Subsystems

The Mars 2 descent module was mounted on the bus/orbiter opposite the propulsion system. It consisted of a spherical 1.2 m diameter landing capsule, a 2.9 m diameter conical aerodynamic braking shield, a parachute system and retro-rockets. The entire descent module had a fueled mass of 1210 kg, the spherical landing capsule accounted for 358 kg of this. An automatic control system consisting of gas micro-engines and pressurized nitrogen containers provided attitude control. Four "gunpowder" engines were mounted to the outer edge of the cone to control pitch and yaw. The main and auxiliary parachutes, the engine to initiate the landing, and the radar altimeter were mounted on the top section of the lander. Foam was used to absorb shock within the descent module. The landing capsule had four triangular petals which would open after landing, righting the spacecraft and exposing the instrumentation.

Question: What exactly were Mars 2's conical aerodynamic braking shield and "gunpowder" engines? I can't understand what these are or how they work, and the potential for the use of gunpowder in an engine is intriguing!

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The "conical aerodynamic braking shield" was an aeroshell.

The "gunpowder rockets" were small solid rockets. A set fired first to spin the vehicle up for stabilization during entry (hence the "control pitch and yaw"), and then another set fired to despin it.

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Reference and image: Soviet Robots in the Solar System, Huntress and Marov, p. 251

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  • $\begingroup$ Great! Any thoughts on the term "gunpowder"? Also note that the if the aeroshell did not function as an ablative heat shield it will be an answer to the linked question as well. $\endgroup$
    – uhoh
    Feb 21, 2021 at 0:46
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    $\begingroup$ I imagine "gunpowder" is a translation infelicity. $\endgroup$
    – Organic Marble
    Feb 21, 2021 at 0:50
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Watch this is an old movie.

At 2:05 - "To maintain this position in the passive part of the trajectory, its powder engines twist around the axis of the descent vehicle."

2:34 - "As soon as the gauge of overloads will inform on a meeting with atmosphere of Mars, powder engines stop lander rotation."

3:16 - "...the engine to steer the parachute to the side turns on." 3:22 - "The bottom part of torus with the engine of soft landing separates."

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  • $\begingroup$ Excellent addition, thank you! Any thoughts on why that NASA page would refer to them as "gunpowder engines"? $\endgroup$
    – uhoh
    Feb 24, 2021 at 3:32
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    $\begingroup$ @uhoh These are some features of the translation of technical terms. Equivalent translation - "solid propellant engines". $\endgroup$
    – A. Rumlin
    Feb 24, 2021 at 16:02

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