Author: Pradeep

There was this interview with M Mohanan, Director of the Liquid Propulsion Systems Center (LPSC). As with all ISRO interviews, I don’t take their timelines very seriously but they usually point to the proper direction in terms of technology advancement.

The interview in Malayalam was done by Asianet’s Arun Raj on the sidelines of National Space Day, held to commemorate the landing of Chandrayaan 3 near the lunar south pole on 23 August 2023. A series of programmes were held discussing the future of the various ISRO missions that I am still going through.

There seem to be many people who were asking for a translation of this interview on X and Reddit. Hence, decided to do it here.

I think ISRO is in an important transition from solid to liquid propellants for their launch vehicles. In this back drop, I think this is an important interview to track.

• Interview with M Mohanan, who took over as Director, LPSC from V Narayanan, who became ISRO Chairman.
• LPSC’s role in Chandrayaan 3 included the development of the landing motors that helped it to land successfully.
• What after Chandrayaan 3? Chandrayaan Follow-on programme.
  • The ultimate mission is landing an Indian on the Moon by 2040, as per the Prime Minister’s vision. Work on this is in progress.
  • Chandrayaan 4 – sample return mission – landing a rover on the Moon – rover will excavate or drill a sample (rock or soil) from the lunar surface, take it back to lander, put it in a module which will take it to the orbiter and then return it to Earth.
  • Chandrayaan 5 – similar to Chandrayaan 4 but will be done in collaboration with JAXA (the Japanese space agency). Launch will be done by JAXA. New satellite propulsion systems are necessary because of the increased mass of the payload. The payload mass for this mission is approximately 6,500 kg. Indian payload masses have been close to 3,000 – 4,000 kg. We are developing the thrusters which are now in the qualification phase.
• Semi-cryogenic engine:
  • We have developed two cryogenic engines successfully – GSLV CUS – 8 ton and LVM3 – 20 ton. SCE capability is comparitively very high. Semicryogenic engine propellant loading is 200 tons and the engine develops a thrust of 100 ton. We are developing a heavy launcher for this purpose in the future.
  • SCE is going to use liquid oxygen and pure kerosene (that we call ISROsene.
  • Engine manufacturing is complex: The temperature regimes and material used for this engine is very different. We have faced issue with qualification and manufacturing with the material used for the engine. We have overcome those issues and have started testing with the Power Head Test Article (PHTA, called the “brain” of the engine). We have successfully completed 4 tests. We are now moving to testing the engine as a whole.
  • We are first going to build the thrust chamber by the end of this year. We are going to build the stage by the end of next year. We are then going to test it in the LVM3. We will replace the L110 engine on the LVM3 with a 1-to-1 replacement. But, the engine will have comparitively higher thrust, that will let us carry a heavier payload to orbit – from the current 4 tons to 5.5 tons. That is our first aim, that we are trying to achieve by end of 2026 or early 2027.
  • Bharatiya Antariksh Station – We are planning to launch this on the LVM3 starting from 2028 and complete the commissioning of 5 modules by 2035. He seemed to imply that we will only be using LVM3 for this.
  • When we need to carry 20 ton payload to orbit or send humans to the Moon and bring them back, we need heavier launch vehicle with the capability to carry 100-120 ton to LEO. Hence, we are building NGLV as well as another launch vehicle in a modular format so that we can add an extra stage if necessary.
  • We are currently planning to use a 7 to 9 engine configuration in the first stage of the NGLV(Not sure if he meant this about the SCE or the LOX Methane engine).
  • We have got approval to develop a single 110 ton LOX Methane engine. We have started testing it since last week. Another test was held on the day of the interview. We will complete the development by the middle of next year at an engine level. Stage building will start as part of the NGLV project and is yet to begin.
  • Electric Propulsion – We are getting a PSLV built by outsourcing it to an industry consortium. The first launch mission is called PSLV-N1. PSLV-N1 will carry Technology Development Satellite (TDS-01). Ordinarily a satellite is put into a 150 x 36,000 orbit. But, this satellite will be placed in a 240 x 18,000 km orbit. The orbit raising of this satellite for circularisation of the orbit of 36,000 km will be done by electric propulsion. This has many advantages. A small thrust can be applied over a longer duration. Also, ordinarily 70-80% of the satellite mass is usually the propellant (fuel and oxidiser). With the use of electric propulsion, we can reduce the mass of the propulsion system from 3200 kg in a 4 ton satellite to a total of 100-150 kg. This includes a battery, an electric propulsion thrusters, and avionics. We have developed, qualifed, and delivered the thrusters successfully. The avionics have been qualified and will be sent for flight testing by the end of this month.
  • PSLV-N1 is scheduled for the end of this year. This mission carries a 300 mN thruster with a 4 kW power. Once this test is successful, we will increase the capacity to a 1 N thrust and 20 kW power system for an all electric propelled satellite. This requires a different battery and new technologies that will need to be developed. This will depend on the success of this mission.
  • Question on Gaganyaan since Mohanan had earlier worked with HSFC. Gaganyaan delays have been because of various reasons. Configuration and readiness of the G1 mission is completed. We plan to have 3 uncrewed missions before the crewed mission. We plan to do the first uncrewed mission, G1, by the end of this year.
  • The HLVM3 stages for the G1 mission are already in Sriharikota. The Crew Module that will help humans stay comfortably in orbit for several days and which can dock with ISS in the future is under preparation. ECLSS sytem is already done. Continued in the point below this.
  • We need to simulate the conditions of the parachute that will be used to return the crew module safely that begins 7 to 8 km over the surface of water.
    • Integrated Air Drop Test with a helicopter – For the first test we will use a helicopter with a simulated crew module and recover from the sea. This will be done this month.
    • Integrated Air Drop Test with a Test Vehicle – We will use a Test Vehicle carry an Orbital Module to a height of 15-17 km. We will drop it and control its descent with a parachute. This will be done in the next 2-3 months.
    • After we do these two tests, we will get a complete idea of landing mission sequence, parachute performance, and mission computer operation. G1 mission will be done following this.
  • Crew Module is getting assembled in URSC, Bangalore. LPSC is working on the Environmental Control and Life Support System (ECLSS) of the Crew Module which will carry the crew. ECLSS will maintain a temperature of 22 degrees C and a RH of 50%, control oxygen, carbon dioxide, oxygen percentage etc. The Cabin Pressure Control System and the Thermal and Humidity Control system is delivered and its integration is in progress. The thrusters of the propulsion system on the crew module and the service module have been tested under various conditions. It’s integration is also complete.
  • Crew Module and Service Module together is Orbital Module. After the integration at UPSC it will be moved to Sriharikota and the mission will be ready to launch.
  • No place for risk. Ordinarily, we focus on quality. A loss of quality is a loss of mission. But, in this case, there is a requirement for a layer of safety over and above just the quality requirements. This has more stringent certification requirements. There is a separate board for clearance of these missions just like for aeroplanes. We are discussing and holding meetings for safety approvals for the G1 just as if it was a crewed mission to prepare for the crewed mission.
  • Instead of TV-D2 for landing tests, we are doing it as a separate project that we call Vertical Take-off and Landing Experiment. The configuration will be similar to the Test Vehicle. The important part of this vehicle will be a throttalable version of the Vikas engine. This version can reduce the thrust of the Vikas engine to 30% of its power by throttling using valves and electronics. We have completed the test of the throttalable engine. We have to build the stage with landing legs and grids (to increase the drag)so that the stage can land. We will begin work on this next year and the landing test can be done within the next 2 years. We have to work out how high it needs to go for the test. The test with this vehicle will demonstrate the technologies needed for reusability of the first stage of the NGLV.