Test Results of the H-IIA Rocket Solid Fuel Rocket Booster (SRB-A) Qualified-type motor ground propulsion test (QM2)

The National Space Development Agency of Japan (NASDA) performed
an SRB-A groundpropulsion test at the Ground Combustion Test Facilities
for Solid Rocket of the Takesaki launch site at the Tanegashima Space
Center at 11:00 a.m. on Friday, Jun. 2, 2000.

The test concluded with gathering the expected data. The test was
confirmed that the problems with the nozzle had been solved by the
change in plan this time. The nozzle had produced much more erosion
than NASDA had expected.

After the test, fragments of CFRP (Carbon Fiber Reinforced Plastic),
which made up the nozzle was scattered. For that reason, NASDA
analyzed SRB-A and scrutinized an image of propulsion test closely.

–Throat Insert fell into the motor case.

–Parts of the upstream side Radiation Shield (made of CFRP) and
the Liner Insert (made of CFRP) at the rear of the Throat Insert
were damaged. These parts matched with the scattered CFRP.

–At the end of propulsion, red-hot material was scattered from the
nozzle.

From the above circumstances, the following phenomena have been inferred:

1. Just as the propulsion ended, the Throat Insert moved to the
upstream side of the nozzle (*).
That caused damage to a portion of the Radiation Shield, which broke
into pieces and was discharged from the nozzle.

(*) The propulsion pressure maintaining the Throat Insert declines
when propulsion is completed. In some cases, the Throat Insert is
pushed to the upstream side by the balance of the gas pressure
that the Liner Insert develops and the binding power of the
Radiation Shield.
It had been anticipated that this could happen, the Throat Insert
to the upstream side had also moved in previous propulsion tests.

2. Because the Throat Insert detached from the nozzle, the rear of
the Liner Insert was exposed and fell off.

Approximately the same amount of erosion on the Radiation Shield
(including scattered CFRP) was seen in previous tests. In the future,
more in-depth mechanism investigations shall be conducted on these
phenomena.

END