On our most recent flight, we performed a test to prove the Crew Capsule could safely land with only two of its three parachutes open. On a nominal flight with all three parachutes deployed, the capsule descends at about 16 mph before firing a retrorocket just a few feet above the ground. This retrorocket firing is what creates the large cloud of dust you see just before the capsule lands, and slows the capsule down to 3 mph before it touches the ground. This last bit of speed is absorbed by a ring shaped crushable bumper made of aluminum honeycomb material mounted on the bottom of the capsule. The ring is made of eight segments.
On this last mission, with one chute intentionally failed, the capsule was descending at 23 mph before firing its retrorocket. The retrorocket took out most of that velocity, and the crushable ring did the rest of the job. Below, you can see a couple of pictures of the crushable after the flight test. The first picture shows it mounted under the vehicle after we lifted it off the ground post-flight. The second picture shows a side view of the eight segments after we removed them from the vehicle. Even with one chute out, the crushable barely crushed. When new, the crushable is about 5.5 inches high and can crush down to less than one inch high, providing a constant deceleration force as it crushes. After the mission, the crushable was still over 5 inches high along nearly the entire circumference of the ring.
We’ve designed the capsule to ensure astronaut safety not just for a failure of one parachute, but even for a failure of two parachutes. In addition to the retrorocket system and the crushable ring, there is an energy absorbing mechanism mounted underneath each seat.