The blogpost Lessons From NASA Disasters: When Curiosity Deficits Kill is about the importance of freedom of curiosity for members of organizations. However it contains many Space Shuttle-related images.

The ones below show the Shuttle SRB's parachuting to Earth and floating end-up in the ocean.

  1. Why do these spent, open-ended (at one end) and possibly air-leaky hollow tubes still reliably float?
  2. Why do they appear to float stably in an upright position rather than on their side?

Space Shuttle SRB splashdown


2nd image's url includes "STS-116_rocket_boosters_NASA_KSC-06PD-2794" and the quoted source for these (and many other STS images) https://howlingpixel.com/i-en/Space_Shuttle_Solid_Rocket_Booster

For comparison, from Scott Manley's https://youtu.be/EH1nyPIvLjI (found in the currently-unanswered question Falcon 9 2nd stage pusher; how far does it continue to extend as it accelerates separation?)

floating Falcon 9 from Scott Manley's video


1 Answer 1


They floated upright because the hollow insides partially filled with water and the aft skirt of the booster was heavier than the front end (it had the hydraulic power units, the thrust vector control system, what is left of the nozzles, etc).

During recovery operations divers plugged the nozzle and air was blown into the booster to "dewater" it.

When sufficient water has been removed from the SRB, the booster will become unstable and float in a log mode.

An inflatable bag on the NP will be inflated, once the SRB assumes a horizontal mode and a de-watering hose will be deployed. Additional air is then forced into the SRB to achieve a pressure differential which will force the remaining water out of the SRB through the dewatering hose. The umbilical is then detached prior to towing operations. A towline is attached to a towing pendant on the nose of the SRB and transit to the refurbishment site is begun.

NP = Nozzle Plug

enter image description here

Image from the 1982 Press Manual

Information from Solid Rocket Booster Retrieval Operations.

Historical note: the dewatering operation was supposed to be done by an undersea robot, but this failed in development, so divers did it throughout the program.

  • 1
    $\begingroup$ Do you know if they had to continue to add air at some rate to compensate for air leaks? I know there were O-rings, but did they always remain air tight after all of the hot exhaust and vibrations? $\endgroup$
    – uhoh
    Sep 7, 2019 at 15:23
  • 1
    $\begingroup$ The document says the air hose was removed prior to towing ops, so if there was leakage, it must have been fairly minor. Also, if there was a significant leak the booster probably would have sunk before the recovery ship showed up. (A couple of SRBs did sink when they hit the water too hard because of parachute failures) $\endgroup$ Sep 7, 2019 at 15:25
  • 1
    $\begingroup$ google's creepy AI just suggested I watch Shuttle's Boosters Recovered in HD youtu.be/Gbtulv0mnlU $\endgroup$
    – uhoh
    Sep 21, 2019 at 1:00
  • 2
    $\begingroup$ @uhoh I've been experimenting with duckduckgo to avoid some of the creep! $\endgroup$ Sep 21, 2019 at 1:03
  • 1
    $\begingroup$ The boosters were built to withstand massive pressures from the combustion process. Any leaks would be catastrophic (Challenger). Seals that are capable of withstanding that environment won't suddenly develop leaks after burnout . $\endgroup$
    – Hobbes
    Sep 21, 2019 at 6:45

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