SSLV News, Discussions, Updates and Reports

Varoon2

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Not an exact one-to-one equivalence, but consider a comparison with a sports team in a play-off situation. The team doesn't win, but it tried hard, came close and overall played very well. The SSLV/ISRO 'played' well, it just didn't 'win'. So they deserve praise for the effort, and for coming close.
 

DEV1729

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bhai noob question but it shouldn't have failed. Itni bar daala hai earth orbit me satellite fir bhi fail High lvl investigation honi chaihye and punish karna chaihye jinhone galti kiya. 100-200 crore se kam nahi hoga ek?
30 crore is the amount which less than the amount seized by ed in partha chatterjee house.
 

Indx TechStyle

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Isro human space foray set for next step
On the Chandrayaan-3 mission, Somnath said that ISRO was looking at a launch window around June-July this year
Credit: Special arrangement
In another four months, India would take its first step to send a human to space with ISRO launching its maiden crew module abort mission by April-May followed by a second such mission after three months and an unmanned mission by 2023 end, clearing the decks for the much awaited 2024 voyage to send an Indian to space.
The next year would see two more abort missions – four such missions are planned to ensure complete crew safety, which is central to the ambitious plan – and a second unmanned mission before a crew of one or two Indian Air Force officers would take a flight to space in an indigenous spacecraft four decades after Wing Commander Rakesh Sharma, who flew in a Russian craft.
"The first abort mission (TV-D1) would be happening around April-May followed by another such mission (TV-D2) three months later. There will be an unmanned mission by the end of the year. Next year, there will be two more abort missions and a second unmanned mission before human space flight,” S Somnath, chairperson of the Indian Space Research Organisation said at a press conference on the sidelines of the 108th session of the Indian Science Congress.
“It is not like sending a satellite to orbit. We cannot take chances when it comes to human beings. We are being cautious and careful. Globally it took about 10 years for countries to develop human space flight capability, which we are doing in four years.”
The ISRO chairman flagged the lack of industrial ecosystem for the space sector as one of the key reasons behind the delays in realising the manned flight mission.
For instance, the space agency needed crucial environmental control and life support systems for the crew module but could not import them because the imported systems were coming with exorbitant price tags and there were no Indian versions available. The ISRO scientists have to develop the systems in-house.
On the Chandrayaan-3 mission, Somnath said that ISRO was looking at a launch window around June-July this year. “All the tests to ruggedise the payload have been completed. The satellite is fully integrated. The orbiter, lander and rover are ready and we are looking at the right slot for the launch by GSLV-MK-III. The next best days are coming in June-July,” he said.
The ISRO chairman said the second development flight of the Small Satellite Launch Vehicle (SSLV) will happen next month. The SSLV flight would be used to test a space-based aircraft monitoring system.
"The ADS-B receiver gets all the details of an aircraft. Currently, the Air Traffic Controller gets these signals, but there are certain blind spots -- about 30% of airspace across the globe -- to which ATC doesn't have access. Now, we have developed a space-based ADS-B technology that would be tested on the SSLV flight," said D K Singh, Deputy Director, Advanced Technology Area, Space Application Centre, Ahmedabad.
The first flight of SSLV in August 2022 was unsuccessful. Once the SSLV is realised, India would be in a position to launch satellites weighing up to 500 kg to low earth orbits within weeks.
Singh said ISRO was also working on a special high-throughput satellite that would expose Indians to the in-flight browsing experience, but it would take another year before the satellite would be ready for launch.
 

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Isro human space foray set for next step
On the Chandrayaan-3 mission, Somnath said that ISRO was looking at a launch window around June-July this year
Credit: Special arrangement
Takeaways:
  1. First abort test in April-May and second in September-October before G1 mission by year end. Same pattern of two abort tests before G2 mission next year.
  2. Crew for Gaganyaan are essentially Indian Air Personnel, confirms officially.
  3. Chandryaan-3 all ready for launch. Launch window falls in June-July and a delay is unlikely unless launcher assembly takes time.
  4. SSLV this February.
  5. Will carry a payload ADS-B to collect aircraft details from 30% of global airspace which is not covered by ATC
Copy pasting messages on relevant threads.
 

spiritb2

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ISRO site has detailed write up on SSLV-D1 failure, preview of SSLV-D2. What do they mean though, by launch in 'first quarter'. Wasn't the launch date set for Feb 10-15. Well, that does fall in the first quarter!

SSLV-D2/EOS-07 Mission: Second Developmental Flight of SSLV (isro.gov.in)

SSLV-D2/EOS-07 Mission: Second Developmental Flight of SSLV

Summary of Failure Analysis of SSLV-D1 Mission & Recommendations for SSLV-D2



Small Satellite Launch Vehicle (SSLV) of ISRO is designed to be affordable and amenable to industry production and will function as a launch-on-demand platform for Mini, Micro or Nano satellites. It is a three-stage vehicle with all solid propulsion stages and liquid propulsion-based Velocity Trimming Module (VTM) as the terminal stage. The launcher also targets many novel features including low turn-around time, flexibility in accommodating multiple satellites, launch-on-demand, minimal launch infrastructure requirements, etc.
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).

Cause of Anomaly

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

SSLV Inertial Navigation System
  • SSLV uses a newly developed inertial navigation system, MEMS Inertial Navigation System or MINS-6S, which consists of 6 MEMS Gyros (for measuring rotation rates) and 6 Ceramic Servo Accelerometers (for measuring accelerations) assembled in a vibration isolated temperature-controlled assembly. The system is also designed with in-built NavIC receiver and also acts as the MINS navigation computer processor for running Inertial Navigation and Aided Navigation software. A novel algorithm estimates the error in the attitude (orientation) introduced due to the MEMS Gyros, position & velocity of the MEMS INS, using the NavIC data and corrects them, so that mission accuracy is achieved. Knowing the health of accelerometer is of paramount importance for the functioning of MINS, as it is used for attitude aiding. The failure detection logic identifies degraded accelerometer (one or all of 6) and isolate the same for improved mission performance.
  • During the SS2 separation event, all the six accelerometers inside the MINS package experienced measurement saturation due to high vibration levels for a short duration. The accelerometers got saturated at different time instants, within the 20 millisecond (ms) interval of data sampling, which resulted in different acceleration values being measured by each sensor. This resulted in high residue values (difference among them) beyond a specified limit for a duration of 2 seconds. The software implementing the Fault Detection & Isolation (FDI) assessed that the sensor outputs crossed the pre-set threshold limit and raised the alert/flag for the salvage mission mode initiation, which is a safety approach for mission. However, the accelerometers were found functioning well after this transient event. The salvage mission mode got fully executed without the support of the accelerometer data and injected the satellite to an unstable orbit due to lower injection velocity (~56m/s less than the required 7693 m/s). Though this is as programmed and expected, if kept observing for longer duration, the residue among the sensors would be within limit and failure logic would not have been executed.
Shock and Vibrations during stage separation
  • The vibrations at the satellite interface as measured during the flight, were well within the pre-flight test specifications except during second stage (SS2) separation event when the Equipment Bay and Satellite interface had dominant vibration response in the first axial mode. The shock response measured at EB during the SS2 separation exceeded the expectations and ground tests levels both in low and high frequency as well as in time duration.
  • Due to this shock, excitation at the MINS sensors was persistent for more than 10 milli second (ms) duration which was not expected. It is generally observed that shock from such events last for about 2 ms, whereas here a shock of 2-3 ms duration and subsequent oscillations lasting for more than 10 ms was observed.
  • Further, based on the flight telemetry data, all the accelerometers were found functioning normally after the transient event till the end of the mission, indicating no damage to them. However due to mission salvage setting by the FDI program, data from these accelerometers were not used for further mission execution.
Satellite injection into an unintended orbit
  • Though the salvage mode was initiated with the purpose of saving the mission, it could not inject the satellites to a safe orbit. The third stage, SS3 ignition was commanded by the sequence program. Subsequently, the vehicle was guided through time-based open loop mode steering without feedback, as the accelerometer data was declared faulty. At the end of SS3 burnout, the satellites were separated safely as programmed. In the implemented salvage scheme, with predefined time-based open loop guidance scheme, the vehicle attitude reference could be erroneous depending on the MEMS Gyro errors. Further, there is no knowledge of the actual velocity of the vehicle as well, since the velocity is computed from accelerometer data. VTM ignition was bypassed as programmed, since it could be a deterrent to the success of salvage option in some cases. The shortage of about 56 m/s at the end of SS3 burn out in final velocity (due to cumulative deficiency in performance of all propulsion stages) and loss in pointing accuracy due to sensor errors, the targeted orbit could not be achieved. This indicates that execution of salvage option in all situations need not always lead to successful placement of satellites in an orbit.

Recommendations & Corrective actions

Change of Separation System

  • The separation system used for separating Second stage from third stage was based on a Circular Expanding Bellow system which shear the rivets and give axial separation velocity. This system is replaced by well proven Marman band system for separation and springs for giving axial separation velocity. The new system is proven to be generating lesser shock and is already used in the separation of third stage.
MINS FDI logic
  • The FDI logic based on the accelerometer threshold is modified to evolve a more realistic approach based on the data generated through system level tests, integrated separation tests and flight. The accelerometer residue logic checking in MINS is modified to handle transient events. Moving average window is modified so that in case of failure identification of multiple sensors in MINS, checking for a longer duration before setting the salvage mode is implemented.
Dynamic characterization and design modification of structures
  • Dynamic assessment of EB & Satellite assembly along with VTM is carried out and structural design modified to increase the frequency of the structures. Modifications in EB deck & Satellite deck were implemented to minimize response to the observed excitations.
Usage of NaVIC data
  • Further, in case of failure of inertial system sensors, the mission will be progressing using NavIC data in a closed loop guidance scheme.
VTM will be in loop for salvage mode
  • In case of failure of inertial sensors and non-availability of NavIC data (for more than 10 sec), an open loop steering guidance will be executed. The propulsive capability of VTM will be considered in this salvage mode also and thrusters will be operated to ensure the minimum required perigee for the mission.
Getting ready for SSLV-D2


The SSLV-D1 was the first developmental mission of this new launch vehicle. The objective of development missions is to prove the launch vehicle design and architecture and to bring out any residual unknowns not identified in the qualifications tests and analysis during its development journey. SSLV-D1 mission demonstrated the satisfactory integrated performance of SSLV in all its systems including its flight through the aerodynamic regime, which is an accomplishment by itself.
Considering the clear identification of the cause of the flight anomaly and suggested corrective actions, the next development flight (SSLV-D2) is planned to be executed complying to the recommendations, its satisfactory implementation, review and approval by the authorized committees.

The second developmental flight of SSLV (SSLV-D2/EOS-07 Mission) is scheduled in the first quarter of 2023 and will launch a total payload mass of about 334 kg including EOS-07 satellite and two co-passenger satellites.

Source: https://www.isro.gov.in/mission_SSLV_D1_summary_D2.html
 
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Vamsi

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Vamsi

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SSLV-D2 integration completed on Feb 7
Launch Authorization Board will meet on Feb 8 i.e today and final launch decision will be taken
vehicle was integrated on 1st launch pad
Launch will be on Feb 10

@Indx TechStyle @Swesh
 

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