Pradeep's Space Newsletter #40
The SSLV-D1 Mission failure
It has been 5 years since we saw the last D1 mission from ISRO. That was the first demonstration flight of the GSLV Mk-III. Today, we witnessed the first demonstration flight of the Small Satellite Launch Vehicle (SSLV).
The mission was to fly two satellites - the Earth Observation Satellite (EOS-2) and a private satellite by SpaceKidz India (AzaadiSat).
The mission ended in a failure to place the satellites in their designated orbits.
While news outlets were focused on ISRO building bigger and more powerful rockets, the SSLV was a side step to building a smaller rocket that could place smaller (~ 500 kg) payloads and launch them faster than a PSLV. PSLV is ISRO’s workhorse rocket that takes about 6 months to assemble and launch. The SSLV could be assembled in 7 days.
The lift-off from the launch pad was smooth. Earlier issues during the static fire test of the SS-1 (SSLV Stage 1) had me worried that this stage may be a point of failure. This stage worked flawlessly.
Problems seemed to begin from the second stage onward. You may see a deviation in the chart if you look carefully.
Source: SSLV-D1 Mission updates from r/ISRO
That last wiggle at the top of the yellow line is believed to be the Velocity Trimming Module and spacecraft tumbling in space. While the graph needs keen eyes, I think looking at the timing chart (designed mission profile vs actual mission profile) will give a clearer picture.
Source: SSLV-D1 flight profile comparison from r/ISRO
My argument is that things go wrong from the SS-1 separation of the first stage (SS-1) onward. It begins as a small variation of 1 second between the predicted and actual time. At the point of the second stage (SS-2) separation, the difference grows to 3 seconds. The third stage (SS-3) burnt a full 12.1 seconds longer than its designed burn time. Perhaps, it was compensating for the loss in the second stage of flight?
The difference between SS-3 separation and VTM ignition was 9 seconds. That difference seems to have been maintained in the new VTM ignition time. The VTM burnt only for 0.1 seconds. The VTM was to burn for 20-seconds to make sure that the satellite are placed in the correct orbit.
The wiggle one sees above in the time vs relative velocity graph is at the beginning of this 9-second window between SS-3 separation and VTM ignition.
ISRO however tweeted that the issue:
The statement issued by Chairman, ISRO - Video.
Now, looking forward to reading the Failure Analysis Committee Report.
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During the PSLV-C53 launch, a big deal was made of the authorization given by India’s space regulator, IN-SPACe to two payloads belonging to India’s private space industry. It is not known on what authority IN-SPACe gave these authorizations. They are not backed by legislation in Parliament.
On the other hand, AzaadiSat which flew on the SSLV did not seem to have gotten such an authorization. They did sign an MoU with IN-SPACe on June 10. Or perhaps, they were in the deleted 2/3 or 3/3 tweets in that tweet thread?
I hope that once IN-SPACe begins to provide these authorizations, they must begin to apply these uniformly to all private sector players. Eventually, I hope they will also provide these authorizations for ISRO spacecraft and launch vehicles, as originally designed.
Was AzaadiSAT built by girl students?
Vasudevan Mukunth says no. This isn’t one of a kind, though. Many of the satellites claimed to have been built by college and university students are mostly like this. India’s university system makes it difficult to actually build satellites.