Solid Rocket Booster Jettison


I believe you are mistaken about the altitude at which the solid rocket boosters (SRBs) are jettisoned. They would never be jettisoned as low as 19,000 ft (6,000 m) except perhaps under some extreme abort scenario. The values used on our site are based on official NASA data for the time, speed, and altitude profile of a typical Space Shuttle launch trajectory.

Typical Space Shuttle mission profile
Typical Space Shuttle mission profile

The time and altitude of SRB jettison can be verified by reviewing the following NASA sites:

Both sources indicate that the boosters separate at an altitude of about 150,000 ft, or 30 miles, about 2 minutes after liftoff. Their momentum carries them to a peak altitude of about 220,000 ft, or 40 miles. They then begin a ballistic freefall carrying them about 140 miles downrange of the launch pad where they are recovered. At an altitude of 15,000 ft, or 3 miles, they deploy parachutes to slow the descent before impacting the water about seven minutes after launch.

Solid Rocket Booster jettison and recovery
Solid Rocket Booster jettison and recovery

The timeline used to create the launch profile we've discussed on our site was obtained from a NASA press kit for STS-30. The key points of that trajectory are summarized below.

STS-30 Trajectory Sequence of Events
Event Mission Elapsed Time
(MET)
[d/h:m:s]
Relative Velocity
[ft/s]
Mach
[-]
Altitude
[ft]
Launch 0/00:00:00 - - -
Begin Roll Maneuver 0/00:00:09 183 0.16 774
End Roll Maneuver 0/00:00:17 365 0.32 2,825
SSME Throttle Down to 65% 0/00:00:30 711 0.64 9,043
Maximum Dynamic Pressure (Max Q) 0/00:00:59 1,368 1.35 35,133
SSME Throttle Up to 104% 0/00:01:02 1,428 1.43 37,284
SRB Staging 0/00:02:05 4,212 3.93 153,405
Negative Return 0/00:03:58 6,915 7.39 319,008
Main Engine Cutoff (MECO) 0/00:08:31 24,286 22.70 362,243
Zero Thrust 0/00:08:38 - - -

Note that the solid rocket boosters are jettisoned at two minutes and five seconds after launch at the point called "SRB Staging." At that time, the vehicle is traveling nearly 3,000 mph (4,600 km/h) at an altitude of 29 miles (47 km).

Solid Rocket Booster being recovered at sea
Solid Rocket Booster being recovered at sea

After recovery, the SRBs are towed back to shore where they are refurbished for use on a future flight. Each booster is designed to complete about 25 flights before it is no longer usable.
- answer by Doug Jackson, 4 July 2004

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