“The problem appeared to be the SSLV’s terminal stage, called the velocity trimming module (VTM). According to the launch profile, the VTM was supposed to have burnt for 20 seconds at 653 seconds after launch. However, it burnt for only 0.1 seconds, denying the rocket of the requisite altitude boost. Two satellites onboard the rocket – the primary EOS-2 Earth-observing satellite and the secondary AzaadiSAT student satellite – separated from the vehicle after the VTM burnt. This means they are likely to have missed their intended orbital trajectories as well, and entered an elliptical orbit instead. This is not the first time for the space agency to witness a setback on its maiden launch missions. PSLV that was dubbed as one of the trusted workhorses for the space agency, was not successful in its first flight way back on September 20, 1993,” said space expert Girish Linganna.
“It wasn’t a major trouble. As far as the first flights go it was almost perfect with a minor hiccup at the end. Next launch should go much more smoothly. Good first flight all in all. We at Pixxel look forward to using the SSLV as well very soon for some satellites in our constellation,” said Awais Ahmed, Founder and CEO, Pixxel. He says that it was a failure of a sensor and the software logic that is supposed to figure out that the sensor failed. “Due to this the fourth burn for the fourth stage couldn’t happen properly and the satellites were deployed in a 356x76 km orbit rather than a 356x356 circular orbit. Since 76 km is very low the atmospheric friction would have burnt up the satellites deployed making them unusable,” added Ahmed.
The expert also said the sensor that failed was sourced from industry and had been used as the redundant sensor in ISRO's other rockets like the Polar Satellite Launch Vehicle (PSLV)."Didn't ISRO do the necessary simulation studies and how was this missed? A faulty sensor triggered the logic," the expert said but ruled out the question of sabotage.
#Thread #Update #SSLV Here We Go: @isro, which couldn’t put put satellites into their desired orbit in its maiden launch attempt of #SSLV yesterday, is studying the various salvage options the rocket can employ to achieve a different result. 1/n
While an expert committee has begun its investigation into Sunday’s mission and would eventually make a set of recommendations, preliminary findings show that the velocity trimming module (VTM) — the terminal stage of the rocket — could not ignite. 2/n
After a smooth lift-off, 1st three stages performed nominally. Mission entered terminal stage where VTM was to ignite & place sats into desired orbit. For this, onboard comps needed info from accelerometers (sensors), based on which VTM's workload would be decided. 3/n
Here, there was an anomaly, which @isro said was caused by a “logic in the rocket to identify a sensor failure and go for a salvage option”. 4/n
I spoke with @isro chief Somanath to understand what transpired in the last leg of the mission. He said: “So far, we’ve learnt that there was no major failure of accelerometers. There are multiple accelerometers… 5/n
...When they show values that don’t match with each other, onboard computers assume there’s a failure & observe accelerometers for 2 secs to check if they become alright. In 2 secs, if values don’t come back to an acceptable level, it’ll declare the accelerometers unsafe… 6/n
…If you use accelerometers that aren’t correct and do the mission, it won’t go in the intended path. Now, assuming that for two seconds the values were not matching, the computer declared a failure… 7/n
…When this happens, there’s an onboard stored prog, a pre-defined path that’s followed. SSLV went on the actual path. Finally when it reached (365km) orbit, the logic did not allow the VTM to fire and make corrections. Hence, the orbit was not achieved,” Somanath explained. 8/n
VTM could not fire because the logic had kicked in after onboard comps didn't receive info from accelerometers (sensors). “And because it had already reached a safe orbit, the salvage option employed decided it would be safe to release the satellites,” one scientist said. 9/n
As part of the detailed study that will now follow, Somanath said, Isro will look at “various salvage options that could have been carried out and which one would be best suited.” 10/n
“When we design a logic, there are values given based on which it gets triggered. Here, there was a trigger that worked and the logic did not allow the VTM to be ignited… 11/n
…This is a minor issue that can be reworked, overall, the findings so far remain that all the new systems worked well and the overall architecture also performed well nominally,” Somanath said. n/n
A former ISRO chairman weighs in about the SSLV failure. Very upbeat, optimistic. Refers to past failures, and how those paved the way for success.
The launch failed due to malfunctioning of the INSScientists are investigating the reasons for the lack of trace of the satellites in the last phase of the launch of the small satellite carrier. It is known that the data is not received from the satellites because the trimming is not done [to attain] 7.8 km per second. It was reported that the Inertial Navigation System (INS) was not working as the speed was reduced to 7.3 kmph. That is why it seems that the liquid fuel [motor] did not burn. Since SSLV is a new launch, a mini inertial navigation system has been installed for it. Scientists at the Vikram Sarabhai Space Center (VSSC) in Thiruvananthapuram are studying why it didn't work.
Villupuram MP wants Lok Sabha to discuss Isro's SSLV mission failure, seeks high level probeVILLUPURAM: Villupuram MP D Ravikumar on Monday moved a motion pleading with the Lok Sabha secretary-general to adjourn the business of the house to discuss the failure of SSLV-D1/ EOS-02 mission.
In his notice, the MP said the failure shows the capabilities of Isro in a poor light. "It shattered the dreams of rural girl students, who were involved in the 'Space Kidz India' programme," said the MP.Pointing out that the country lags in space economy, he said the United States has around 40% shares in the global launching services market while Europe accounts for 25% and Russia for 20%. India has less share (2%) in the 'launching services' market, he said and added that the first developmental flight failure would make the country's position in the global market worse.
https://economictimes.indiatimes.com/news/india/isro-to-launch-indias-newest-rocket-sslv-tomorrow/articleshow/93386908.cms [06 Aug 2022]QuoteWith the new included in its product lineup, ISRO will have three rockets -- Polar Satellite Launch Vehicle (PSLV) and its variants (cost about Rs 200 crore), Geosynchronous Satellite Launch Vehicle (GSLV-MkII and Mk III) and its variants (cost Mk II about Rs 272 crore and MkIII about Rs 434 crore) and SSLV (Development cost of three rockets about Rs 56 crore) and production cost may go down later. Cost of manufacturing 3 SSLV is 56 crore! That's ~18 crore per SSLV, $2.2M at today's exchange rate.
With the new included in its product lineup, ISRO will have three rockets -- Polar Satellite Launch Vehicle (PSLV) and its variants (cost about Rs 200 crore), Geosynchronous Satellite Launch Vehicle (GSLV-MkII and Mk III) and its variants (cost Mk II about Rs 272 crore and MkIII about Rs 434 crore) and SSLV (Development cost of three rockets about Rs 56 crore) and production cost may go down later.
The center has allocated a budget of Rs 169 crore to the project which covers the cost of developing the rocket and conducting three experimental launches to verify the system and Isro had factored the contingencies ahead of the launch.
https://timesofindia.indiatimes.com/india/villupuram-mp-wants-lok-sabha-to-discuss-isros-sslv-mission-failure-seeks-high-level-probe/articleshow/93429954.cmsQuoteVillupuram MP wants Lok Sabha to discuss Isro's SSLV mission failure, seeks high level probeVILLUPURAM: Villupuram MP D Ravikumar on Monday moved a motion pleading with the Lok Sabha secretary-general to adjourn the business of the house to discuss the failure of SSLV-D1/ EOS-02 mission.
Quote from: vyoma on 08/09/2022 12:27 amhttps://timesofindia.indiatimes.com/india/villupuram-mp-wants-lok-sabha-to-discuss-isros-sslv-mission-failure-seeks-high-level-probe/articleshow/93429954.cmsQuoteVillupuram MP wants Lok Sabha to discuss Isro's SSLV mission failure, seeks high level probeVILLUPURAM: Villupuram MP D Ravikumar on Monday moved a motion pleading with the Lok Sabha secretary-general to adjourn the business of the house to discuss the failure of SSLV-D1/ EOS-02 mission.Apparently, a member of the Opposition, from a district near Sriharikota?
CHENNAI: ISRO has said that a special committee will study the failure of India's first SSLV-D1 short-range satellite launch. The announcement is that a new launch will be made within four months after the technical problem is resolved. The next launch will be after making necessary changes based on the investigation findings of the special committee.
Where was this logic which did not identify the sensor failure? Was it in the newly introduced velocity trimming module?It is not the logic of the velocity trimming module. This is a logic of the launch vehicle. When something is not working very well, the rocket will have a salvage option.
In this case, what happened is that the measurement of the accelerometer showed some anomaly just at the point of the separation of the second stage. When it showed such an anomaly, the internal computer felt that the accelerometer had failed. Then it triggered something called the salvaging operation.
What it will do next is instead of closed loop guidance, it will initiate what is called the open loop guidance.
There is already a path written in the computer that you should go through this path to reach the satellite. … So it does not look for acceleration data but [the rocket] will simply go in that path. Once it is going like that, the ability to put the satellite in the correct orbit is slightly diminished.
So what happens is that at the end of the next stage firing, the computer believes/assumes that “I cannot go further but somehow separate the satellite after the burning of this motor is concerned.
But the solid motor cannot be stopped midway. The computer will wait until the firing of the solid motor, currently firing, is completed. The anomaly happened at the end of the second stage. So the computer wants the third stage firing to complete. As soon as it is completed, the satellites are injected into orbit. It did that.
So there was really no issue with the accelerometers. They were healthy even afterwards.
You don’t have to declare it a failure. You can wait for a little more time and then have a relook at it. We have thought about it.For two seconds this anomaly existed. After two seconds, it came back to normal. Unfortunately, the computer declared that it was a failure within those two seconds.
There is an unknown thing residing in this whole algorithm. Why two seconds? If it had been three seconds, the mission would not have been like this. If the level of isolation was a little higher, it would not have happened.
Probably, if we had changed the threshold element, the mission could have been saved.
The first developmental flight of Small Satellite Launch Vehicle (SSLV) lifted off from Satish Dhawan Space Centre (SDSC) on 7th August 2022 at 09.18 Hrs IST. The objective of the mission (SSLV-D1/EOS-02) was to inject EOS-02 satellite of ISRO into a circular orbit of 356.2 km with an inclination of 37.21°. Azaadisat, a student satellite was also accommodated in the mission, authorized by IN-SPACe.However, the spacecraft were injected into a highly elliptical unstable orbit due to a shortfall in velocity, leading to their decay and deorbiting immediately, in spite of normal performance of all solid propulsion stages. The orbit achieved was 360.56 km x 75.66 km with an inclination of 36.56.Initial investigations with the flight data indicated that the lift-off of SSLV D1 was normal along with normal performance of all solid propulsion stages. However, the mission could not be achieved due to an anomaly during the second stage (SS2) separation, which triggered a mission salvage mode (which is a procedure adopted to attempt minimum stabilized orbital conditions for the Spacecraft in case of an anomaly in the vehicle system).Subsequent detailed analysis of the flight events and observations ranging from countdown, lift-off, propulsion performance, stage separations and satellite injection revealed that there was a vibration disturbance for a short duration on the Equipment Bay (EB) deck during the second stage (SS2) separation, that affected the Inertial Navigation System (INS), resulting in declaring the sensors faulty by the logic in Fault Detection & Isolation (FDI) software
