Bangalore: Non-availability of liquid hydrogen
supply to the thrust chamber of the main engine could have
resulted in failure of the third developmental flight of
Geosynchronous Satellite Launch Vehicle from Sriharikota on
April 15, a failure analysis committee has found.
The flight of GSLV-D3 primarily meant for testing of
indigenously developed cryogenic upper stage (CUS) had
failed to achieve the mission objectives following which ISRO
had instituted a two-tier process to carry out an in-depth
analysis of the flight performance and identify the causes of
the failure and recommend corrective measures.
As per review of the findings by the `National Group of
Eminent Experts`, though the ignition of the CUS main engine
and two steering engines were confirmed normal, the thrust
build up did not progress as expected "due to non-availability
of liquid hydrogen (LH2) suppy to the thrust chamber of the
main engine", an ISRO release said.
The failure is attributed to the anomalous stopping of
fuel booster turbo pump (FBTP). "The start-up of FBTP was
normal. It reached a maximum speed of 34,800 rpm and continued
to function as predicted after the start of CUS. However, the
speed of FBTP started dipping after 0.9 seconds and it stopped
within the next 0.6 seconds," it said.
Two plausible scenarios have been identified for failure
of FBTP, gripping at one of the seal locations and seizure of
rotor and a rupture of turbine casing caused probably due to
excessive pressure rise and thermal stresses, it said.
As per the review, following a smooth countdown, the
lift-off took place at 1627 hrs (IST) as planned. All four
liquid strap-on stages (L40), solid core stage (S139) and
liquid second stage (GS2) functioned normally, it said.
The vehicle`s performance was normal up to the burn-out
of GS-2, that is, 293 seconds from lift-off, the release said.
Altitude, velocity, flight path angle and acceleration
profile closely followed the pre-flight predictions. All
onboard real time decision-based events were as expected and
as per pre-flight simulations, it said.
The navigation, guidance and control systems using
indigenous onboard computer Vikram 1601 as well as the
advanced telemetry system functioned flawlessly, it said.
The composite payload fairing of 4 metre diameter inducted
first time in this flight, also performed as expected.
Performance of all other systems like engine gimbal
control systems and stage auxiliary systems was normal, it
said.
The initial conditions required for start of the
indigenous CUS were attained as expected and the CUS start
sequence got initiated as planned at 294.06 seconds from
lift-off, the release said.
Ignition of the CUS main engine and two steering engines
have been confirmed as normal, as observed from the vehicle
acceleration and different parameters of CUS measured during
the flight. Vehicle acceleration was comparable with that of
earlier GSLV flights up to 2.2 seconds from start of CUS, it
said.
However, the thrust build up did not progress as expected
due to non-availability of liquid hydrogen (LH2) supply to the
thrust chamber of the main engine, it said.
Following the review, "a series of confirmatory ground
tests are planned", the release said.
After incorporating necessary corrective measures, the
flight testing of indigenous cryogenic upper stage on GSLV is
targeted within a year, it said.
In the meantime, the next two GSLVs would fly with the
available Russian cryogenic stages, it said.
-PTI
