[funkysquid]

That's what I thought as well, but watching some other videos on their site, they say the boost happens in "the last second" https://youtu.be/xYYTuZCjZcE?t=2m34s. Any sign of thrust before landing really isn't visible in that video either. So unless they've never actually fired it successfully and we just don't know what it looks like, it's possible that it's just so close to touchdown that we can't distinguish the thrust from the landing.

I'm assuming that decelerating by 13mph over < 1s is still quite a bit better than by 15mph instantly? But I really don't know.

[diggernet]

I suppose that a last-instant firing is a plausible explanation, and would greatly reduce physical damage to the capsule. But then the talk of a "gentle" 3mph touchdown is conveniently ignoring the 16->13 deceleration a split second before. As you say, it's likely preferable to 15->0, but I suspect not a whole lot more pleasant to experience. The astronauts would probably not even notice the actual touchdown an instant later.

[phire]

The goal is to stretch out the deceleration. Instead of going from 16 to 0 instantly (probably more like 1/10th of a second when you count the capsule deforming), it's going from 16 to 0 over a much larger fraction of a second.

It's probably the difference between running full speed into a brick wall and running full speed into a large foam pad.

The foam pad decelerates you in less than a second, but it's a whole lot more comfortable than the brick wall.

[hanoz]

I'm sure there's no deceleration at all at the beginning of the last second, there's no slackening of the lines for example, but it does look as if there's some sort of thrust brake in the last tenth of a second or so, somewhat in lieu of a crumple zone I suppose.

http://rowvid.com/?v=bqUIX3Z4r3k&t=4232&s=0.25

[diggernet]

Thanks. I always forget about RowVid...

In frame-by-frame, you can see that the capsule is still descending when the first dust appears. To my eye, seems to be about 1/3 to 1/2 second later that the capsule stops. So, ok, retro-thrust. (But still giving quite a jolt to the poor meat-bags.)

[BFatts]

I thought 20mph was maximum survivable rate of decent?