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38

Keeping a burnt-out stage attached doesn't hurt until it's time to start the next stage. In fact, keeping it attached until shortly before it's time to ignite the next stage can improve the total launch delta V. Stage three separation occurred at an altitude of 184 km. There's still air up there. It's not very dense air, but for a vehicle going at close to ...


33

Why would these be used instead of just using a larger first stage? Strapping on differently-sized boosters allows variance in payload mass without redesign of the first stage. The PSLV has flown with no (PSLV-CA), small as shown (PSLV-G), or big (PSLV-XL) solid boosters. PSLV-CA (no boosters) - can deliver 1100 kg to 622 km sun-synchronous orbit PSLV-G (...


16

The coasting period is certainly to perform a Gravity Turn. It is a trajectory optimization that uses gravity to steer the vehicle onto its desired trajectory. ... the thrust is not used to change the ship's direction, so more of it is used to accelerate the vehicle into orbit. Once the vehicle has coasted into the right angle, P4 ignition takes ...


12

PSLV is a bit of a weird duck because it's a transitional step from small solid-rocket designs to larger ones that rely more heavily on liquid rocket engines with higher specific impulse. It doesn't represent an uncompromised "clean sheet" optimal design. ISRO's first two orbital launcher designs, SLV (1979-1983) and ASLV (1987-1994), were small, not-very-...


11

                                                       ISRO's MOM lifting off (credit ...


11

Any rocket flight will involve a burn in it's final orbital position. If you want to enter a 500km orbit your engine will shut down at 500km up. The profile shows it needs nearly 19 minutes to reach altitude but the rocket burn times only add up to 15 minutes. You can't magically make it get there in 15 minutes because you don't have extra fuel. Thus the ...


10

Kerbal Space Program, the video game, teaches us that it is most effective to thrust at apoapsis (highest point of orbit) to increase our periapsis (lowest point of orbit). Waiting to fire the next stage there will make better use of fuel. Note that you want all the force applied at apoapsis, so you want to burn a little before and after it, since it is a ...


9

According to this article, those are insulation panels, and they're simply lightweight enough to not damage the rocket at the relatively low speeds it's moving in the initial seconds of flight. The insulation keeps the upper-stage liquid propellants from boiling or freezing as the ambient temperature changes -- the oxidizer, N2O4, in particular, is liquid ...


9

The key phrase is "satellites separated from the final stage safely without colliding into each other" Let's break that into two pieces: Satellites Separated From Each other- In order to do this, it takes time, power, and attitude adjustment.Also, they have to be arranged such that all of the satellites can be separated from each other. Most of these were ...


8

The answer already posted is excellent. All I want to add is a follow-up question you might want to ask, and my answer to it. Q: OK, so those in particular aren't boosters. But would it ever make sense to use lots of tiny boosters instead of one big one? A: Yes, for two main reasons. One is the extreme expense of anything involved in space flight, and ...


8

"CLG INIT" stands for "closed loop guidance initiation", and means that the launcher is switching into a mode where it actively steers based on its current trajectory rather than a fixed, unconditional program (referred to as "open loop guidance"). In the early part of flight, it is safer to use a "pitch-versus-time" or similar simple logic to guide the ...


6

Yes, but to do so they're having to make significant compromises to the mission. It was originally intended to fly on India's next generation, significantly higher performing, Geosynchronous Satellite Launch Vehicle (GSLV) but delays and problems (3 of 7 flights have failed catastrophically, only 2 were fully successful) in that program forced them to use ...


5

From the beginning of the Wikipedia article that you linked in your question (bolds mine): The Polar Satellite Launch Vehicle, commonly known by its abbreviation PSLV, is an expendable launch system developed and operated by the Indian Space Research Organisation (ISRO). It was developed to allow India to launch its Indian Remote Sensing (IRS) satellites ...


5

Some "coasting" phases are designed to limit the aerodynamic stresses on the spacecraft. The US space shuttle is an example of this. After around 26 seconds the main engines are throttled back for the next 34 seconds. In actuality this is called a "Thrust Bucket". While this isn't a true "coast phase" because the solid rocket boosters are still burning, it ...


4

I would have expected some kind of fin... How do these two cylindrical "pods", symmetrically placed on either side of a cylindrical vehicle, contribute to its aerodynamic stability? Any source of drag placed well behind the center of gravity of the launcher will improve aerodynamic stability. The advantage of fins over cylindrical pods are that ...


4

The blue boxes on upper deck are cubesat deployers by ISIS. One that can house four 3U cubesats is called 'Quadpack' https://www.isispace.nl/products/cubesat-microsatellite-deployers/ ISRO/Antrix also provides its own set of deployers and separation mechanisms for smallsats. Here's a brochure for those. https://web.archive.org/web/20170512132239/http://...


4

One reason to stay attached and coast is to let the lower stage finish it's burnout. One of the early SpaceX launch tests failed because they separated too soon. There was still residual fuel exiting the nozzle after separation and the first stage bumped into the second stage. So on the next launch, they lengthened the attached coasting time, to be sure the ...


3

Originally, MOM was going to use the GSLV to launch. The GSLV has about 50% more capacity than the PSLV. As a result, a few things had to be cut back from the mission, including the payload, removal of a direct to Mars orbit, among others.


1

This highly annotated photo says they are separation motors aka "retrorockets". Also Ullage & Retro Rockets, attached to the outer surface of the PSLV, are another interesting mechanism utilised in the Jettison process. The PSLV uses 12 Retro Rockets - 8 for Stage I & 4 for Stage II; while 4 Ullage Rockets mounted on the body of Stage II ...


1

This excellent answer lists a number of different cubesat deploy mechanisms used on PSLV-C43. One could try to check each of their deploy velocities, my guess is that they will be in the ballpark of 0.5 or 1.0 meter/sec. Guessing 1 cubesat every minute,that's 30 to 60 meters from one to the next. Watching the video PSLV-C43 / HysIS Onboard Camera View cued ...


1

At the moment of release from the dispenser on the launch vehicle or other carrier spacecraft the CubeSats will be very close. After that they will start to naturally separate due to a variety of reasons: CubeSats, per the CalPoly standard, are supposed to have small springs that push them apart from other CubeSats in the same dispenser tube The launch ...


1

Created a python code to generate the acceleration, dynamic pressure profiles for the launch vehicles PSLV and GSLV Mk-3. Plots, source and explanation are in my git location https://github.com/ravi4ram/Launcher-Profile Would love see comments on drawbacks and improvements.


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