# How fast do Russian/Chinese space capsules fall? **URL:** \ **Category:** Factual Questions\ **Created:** [June 26, 2013, 8:36pm UTC](https://boards.straightdope.com/t/how-fast-do-russian-chinese-space-capsules-fall/661985 "2013-06-26T20:36:28Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Earl\_Snake-Hips\_Tucker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/earl_snake-hips_tucker/32/3269_2.png) [@Earl\_Snake-Hips\_Tucker](https://boards.straightdope.com/u/Earl_Snake-Hips_Tucker)\ **Post date:** [June 26, 2013, 8:36pm UTC](https://boards.straightdope.com/t/how-fast-do-russian-chinese-space-capsules-fall/661985/1 "2013-06-26T20:36:28Z")
I just saw a video of the landing of the first Chinese woman in space. Before they fire the braking/retro rockets, how fast is the capsule falling? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 26, 2013, 9:05pm UTC](https://boards.straightdope.com/t/how-fast-do-russian-chinese-space-capsules-fall/661985/2 "2013-06-26T21:05:02Z")
According to[this page](http://www.braeunig.us/space/specs/shenzhou.htm) about the Shenzhou it’s about 8 m/s before the retro-rockets are fired, or just under 18mph. > [@](#): > > Landing system: At an altitude of 10 km the parachute hatch is jettisoned and two pilot parachutes deployed. These pull out the drogue parachute, followed by the ring-sail main parachute that has an area of 1200 m2 and a mass of 90 kg. A back-up parachute with an area of 760 m2 is provided. Below 6 km altitude the heat shield is jettisoned, exposing a gamma ray altimeter and the four nozzles of the soft-landing retrorockets. As the capsule approaches the ground, the capsule converts from single-point to two-point suspension under the main parachute, and its vertical velocity declines to 8 m/s. The altimeter ignites four solid propellant retrorockets at one meter above the ground, reducing final impact velocity to 3.5 m/s. In case of failure, the crew seats are fitted with shock absorbers to guarantee a survivable landing. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [June 26, 2013, 9:29pm UTC](https://boards.straightdope.com/t/how-fast-do-russian-chinese-space-capsules-fall/661985/3 "2013-06-26T21:29:36Z")
Using the formula v^2 = 2ad, v=8m/s, a=g=9.81m/s, then d=(64)/(2)(9.81)=3.3m or just over 10 feet Rough rule of thumb I recall, a typical parchute drop is equivalent to jumping 10 feet - the best compromise between speed of descent and safety. Of coure, modern recreational parachutes are wings with flar capability so that is much less relevant. And safer… I’m surprised since they use retro landing rockets, they don’t make the drop speed higher; but I guess that’s in case of the chance of landing rocket malfunction. ---
**Author:** ![lisiate](https://avatars.discourse-cdn.com/v4/letter/l/f05b48/32.png) [@lisiate](https://boards.straightdope.com/u/lisiate)\ **Post date:** [June 26, 2013, 9:59pm UTC](https://boards.straightdope.com/t/how-fast-do-russian-chinese-space-capsules-fall/661985/4 "2013-06-26T21:59:25Z")
Seems like prudent redundancy to me. A 28kph landing would be unpleasant, but very survivable. ---
**Author:** ![Earl\_Snake-Hips\_Tucker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/earl_snake-hips_tucker/32/3269_2.png) [@Earl\_Snake-Hips\_Tucker](https://boards.straightdope.com/u/Earl_Snake-Hips_Tucker)\ **Post date:** [June 27, 2013, 12:19am UTC](https://boards.straightdope.com/t/how-fast-do-russian-chinese-space-capsules-fall/661985/5 "2013-06-27T00:19:42Z")
Thanks, all.