Indian Space Program: News & Discussions

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From user "Prayash" om Other Forum.
Screengrab from the RISAT-2B launch :

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Is this the logo of the newly formed space command ?
 
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It appears PSLV second stage has also switched to electro-mechanical actuation for Vikas gimbal.

Close-ups of PSLV C46 second stage appears to confirm that from PSLV-C44 onward, PS2 is with electro-mechanical actuator for gimbaling instead of electro-hydraulic one. We know that from GSLV F08 onward, GSLV second stage (GS2) switched to electro-mechanical actuation for gimbal and it was just matter of time that PSLV's PS2 followed due to similarity in PS2 and GS2.

Should be lighter and with less complexity. To quote ISRO Chairman for GSLV F08
"On introduction of electromechanical actuation system in place of electrohydraulic actuation in the second stage of the rocket, Sivan said the new system is simpler and more robust, which increases the vehicle’s reliability."​

Close up of image from PSLV C46 gallery

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Snapshot from PSLV C46 curtain raiser

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Older system on PSLV C42

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More on ISRO's TVC actuators :

Details on Linear Electro-Mechanical Actuator for TVC

Electro-mechanical actuators (EMAs) are finding increased use in the field of Thrust Vector Control (TVC)of launch vehicles. In earlier days, electro-hydraulic actuators were used especially in the lower stages of the launch vehicles where there is a requirement for large actuation forces. However, electro-mechanical actuators are being scrutinized for this purpose in an effort to provide lighter, cleaner and more reliant control actuators.
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The power of electro mechanical actuators was limited by the ability of drive electronics to handle the large electrical power, availability of high discharge light weight batteries and non-availability of high torque motors. The recent developments in Lithium ion batteries with high energy density have made usage of high current / power possible in launch vehicles.

SYSTEM CONFIGURATION
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Engine will have one actuator for one plane (pitch or yaw) gimballing and will have two actuators for two plane gimballing (pitch and yaw). Two engines with two actuators mounted on each engine will provide three plane gimbal controls (pitch, yaw and roll).
The following are the specifications that have been used as design input.

  1. Max angular deflection, θ : 6 deg
  2. 10% system bandwidth, f : 4 Hz
  3. Engine Inertia, Ie : 4000 kg-m 2
  4. Control arm length, L : 1100 mm
ACTUATOR CONFIGURATION
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The actuator configuration consists of a housed 3 phase quadruplex brushless DC (BLDC) torque motor driving a roller screw through spur gear based compound gear train. The rotational motion of electrical motor/gear is transformed in the linear motion by constraining the rotational motion of the roller screw nut. The linear motion of roller screw nut is extended to the engine by piston which is rigidly connected to roller screw nut.
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A LVDT (Linear Variable Differential Transformer) sensor, with probe sliding inside the roller screw and being rigidly connected to the piston which follows the motion is used as the linear position feedback sensor to close the position control loop.
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Lubrication is provided to the gears and other moving elements by grease plating the components before assembly. Krytox grease based on perfluoropolyether oils is used since they can survive continuous high temperatures up to 260oC and provide exceptionally long life time. The connectors used for electrical connectivity of the actuator to the drive electronics belongs to high quality MIL-38999 III series.

BATTERY CONFIGURATION
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Batteries are the power source for electro mechanical actuators. Lithium ion batteries have been selected for use in this configuration mainly due to their ability to handle large currents and higher energy density.
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Each coil of the BLDC motor can demand a maximum of 25 A, but for a short duration only. After taking into account the power demand of an actuator undergoing a typical flight duty cycle, the configurations that can be used were found to be either two 80 AH batteries or four 40AH batteries. Four 40 AH batteries were selected and connected in such a way that each battery is powering one coil of the motor. Hence, in case of a battery failure, each motor will still have three healthy coils which can cater to the supply of adequate control force and ensure a successful mission.

DESIGN :

Screenshot (217).png



Source :
https://web.archive.org/web/2019052...0af0/0cd520371bb5be95d60cda797b46a460eab3.pdf
 
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Blast from the past :

Phuket in Thailand is an island on the Andaman sea. Every time ISRO launches something they warn Thai authorities about debris from the falling rocket stages.
For example this is a news report for Thailand when ISRO was about to launch the Mars Orbiter Mission(MOM)-1 : Ships, planes north of Phuket warned of possible Indian rocket fallout | The Thaiger

Now in 28th March 2015 during the launch of a IRNSS satellite(the IRNSS 1-D) from a PSLV(PSLV-XL-C27) the lower stage of the rocket separated and started falling down. As it fell it began to burn up.

If you type in Indian PSLV booster crashes into ocean off the coast of Phuket into google. There will be a Thai forum where people have discussed sightings of a bright flash before a PSLV stage crashes into the ocean.

Here is the forum, where Thai people went on a search and rescue operation thinking the booster was a plane. Some Thai locals thought it was a mystic NAGA thought to live in the ocean!!:ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO:OMG!! They are a lot like us aren't they.:ROFLMAO::ROFLMAO::ROFLMAO:

There are also some pics of the falling booster on the forum!

Here is the link : Lights of unknown objects over Phuket sea
 
GuardianRED said:
s4-jpg.6789


Interesting Markings
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Mission logos. Every mission has some. Usually designed by labs/facilities directly involved with the mission. Here is the MOM-1 mission logo on the fairing.
1558516012685.png
GuardianRED said:
dummy-jpg.6790


From the Commentators reports - these are Dummy Strap- On's
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From what I've heard there is an incremental improvement program for PSLV. I've posted above about the new gimbal system which is an improvement over the previous system. Similarly these dummy straps will become standard at some point of time. Consider this a flight test/separation test of the new strap ons, the checkered pattern is usually associated with flight testing. There will be fire tests as well. These straps are lighter and have some aerodynamic improvements. You can see them if you compare them with the other straps.
GuardianRED said:
logo-jpg.6800


@Gautam - Logo for RISAT - 2B
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Oh so its a project logo. Many thanks for the find.

Project logos are not the same as mission logos. Each satellite has at least one project logo. In case of large projects(like Mars orbiter,moon orbiter), each instrument has a logo of its own. Here is the logo of a Mars orbiter instrument named MENCA.
1558516925322.png
 
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Gautam said:
Mission logos. Every mission has some. Usually designed by labs/facilities directly involved with the mission. Here is the MOM-1 mission logo on the fairing.
View attachment 6801

From what I've heard there is an incremental improvement program for PSLV. I've posted above about the new gimbal system which is an improvement over the previous system. Similarly these dummy straps will become standard at some point of time. Consider this a flight test/separation test of the new strap ons, the checkered pattern is usually associated with flight testing. There will be fire tests as well. These straps are lighter and have some aerodynamic improvements. You can see them if you compare them with the other straps.

Oh so its a project logo. Many thanks for the find.

Project logos are not the same as mission logos. Each satellite has at least one project logo. In case of large projects(like Mars orbiter,moon orbiter), each instrument has a logo of its own. Here is the logo of a Mars orbiter instrument named MENCA.
View attachment 6802
Click to expand...
I do know that they are Mission Specific Markings on the Fairing - the ONLY DIFFERENCE - that is THIS CASE - There isn't a close up of these on any released info :D
 
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GuardianRED said:
I do know that they are Mission Specific Markings on the Fairing - the ONLY DIFFERENCE - that is THIS CASE - There isn't a close up of these on any released info :D
Click to expand...
I know, awful lot of secrecy around this sat. If I recall, there hasn't been pics of the satellite in assembly released. All this secrecy remind me of the Microsat-R. Standard thing with all military or dual use satellites.
 
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