NASASpaceFlight.com Forum
International Space Flight (ESA, Russia, China and others) => Indian Launchers => Topic started by: K210 on 06/09/2013 09:49 am
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As per various sources ISRO is planning on conducted a third static firing of the S-200 booster some time this year.
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Yeah they have plans to conduct more tests of S200 boosters and L110 to prove reliability for the human space flight program.
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Well, it's interesting - neither Russia nor China have gone in for SRBs for their spaceflight programs, while NASA, ESA and now soon even ISRO are using SRBs.
What is the technical case for and against SRBs?
No throttle control, but how much throttle control do you really need during early ascent phase?
Meanwhile, you get lots of thrust.
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Don't forget JAXA! The supposed advantage of SRB's is their simplicity which implies a low cost.
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No throttle control, but how much throttle control do you really need during early ascent phase?
Meanwhile, you get lots of thrust.
That's a bit harsh. You can profile the grain composition and/or geometry to effectively give you throttle control by varying the surface area that's burning. Of course, it's not closed loop control, and there's no switching it off...
Cryogenics aside, I don't think other liquids have as much bang for the buck as solids. Even if they did, it's probably offset by the increased mass of the plumbing. Given that we don't seem to have a handle on turbopumps (heck, we're yet to develop a turbojet - arguably lower on the technology maturity ladder - ref. the Kaveri Engine), cryogenic propellant storage, and its processing; it's almost a no-brainer that anyone in ISRO who's looking at programs from a vehicular development and commissioning perspective - with a tight timeline - would go for solids. At least as far as high thrust requirements are concerned.
Variations from performance in ascent are often overcome by the upper stages.. and for a nascent manned mission - where mission objectives are simply to prove ECLSS viability (hopefully, re-entry has been proven already lol). Maybe you'll have some research activity thrown in - but at the end, what hill you climb doesn't seem to be as important as long as it's high enough. We're not docking, assembling or building to be worried about precise orbits (Solar Beta angles, and ground communications [as we don't have a TDRSS] notwithstanding). Even if we wanted precision, making up greater distances with upper stages turns out to be more "efficient" (in quotes, because there's always a cost: greater time, and the cost of getting this correctional propellant to orbit/shortened mission span), given the lower mass of the vehicle, reduced atmospheric resistance, and possibly greater burn efficiency (analogous to ion engine 'efficiency' being greater than other engines). Since this can be done with small liquid engines, there's been no real impetus for us to get going on a massive liquid rocket motor.
This isn't out of line with previous evolution of launch vehicle families either.
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SRBs are preferred choice mainly because they provide copious thrust during initial stages of flight, they are simple in design and far less prone to errors and cheap to design & handle.
ISRO has invested heavily in building infrastructure and human resource for solids over the years, starting from its early days. So as far as ISRO is concerned, solids will be around as long as expandable LVs are around.
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Can SRBs be used for quick traversal of the Van Allen radiation belts?
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Can SRBs be used for quick traversal of the Van Allen radiation belts?
why would they be any different than liquid systems? Both solid and liquid systems can be built to provide the required thrust and required impulse. Solids have been used as upper stages for many types of missions. See Delta II and shuttle upper stages
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Fair enough - I guess I thought solids are considered heavier payload-wise and inferior on Isp, and thus better to use them up on the early portion of the trajectory to quickly discard them asap.
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Can SRBs be used for quick traversal of the Van Allen radiation belts?
I think it is very much possible with space qualified solid propellants as operating in space comes with its own set of challenges. ISRO has used solids in space around moon. The de-orbit motor for Moon impact probe (MIP) was a solid motor and ISRO had to develop a space qualified solid propellant for that.
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No throttle control, but how much throttle control do you really need during early ascent phase?
Meanwhile, you get lots of thrust.
For a human launch system, being able to cut the engines helps out in some emergency scenarios.
Also, solids can have vibration issues, particularly when you use only a solid for your first stage. This was the biggest single problem with NASA's Ares I. Vibrations can make it hard for humans to function, can break things in the upper stages, and in extreme cases even cause direct physical harm to passengers.
Another disadvantage of solids is that your vehicle is always fully fuelled. From the moment vehicle integration starts, there's always some risk of the whole thing blowing up. With liquids you can wait until everything's ready on the pad with everything checked out and fuel up just before liftoff.
On the other hand, solids can't leak like liquids can. Liquids are more complex. If a pump shuts down or a pipe breaks, a liquid engine might have to shut down, ending the mission and leading to a risky abort scenario. A solid is never going to accidentally shut down once it is lit.
Both solid stages and liquid stages can and have exploded in flight, so that danger is there for both, and it's not clear one is less risky than the other.
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Given that we don't seem to have a handle on turbopumps (heck, we're yet to develop a turbojet - arguably lower on the technology maturity ladder - ref. the Kaveri Engine)...
Are you saying that the turbopumps in the storable Vikas engine on PSLV and cryogenic CS engine on GSLV Mk.II are not made in India?
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Sorry I wasn't clear. I'm sure assembly happens in India, and although I wouldn't be able to give you a breakdown of the components that we make ourselves (vs the ones we import), I believe that we're quite self-reliant on the manufacture too.
All I'm saying is that if we were to go by the development timelines of other space agencies - and note the number of liquid motors designed and flown, or even just the design iterations for the same motor - before said agency moved on to make motors for a different thrust-class (say First stage vs Orbital Insertion / 2nd Stage) : we've still got a long way to go.
The Vikas has been in development since the '70s. The French were helping us out in the beginning. The CS engine for the GSLV is Russian, and all we did for the first launch was integrate it into the LV (Yes, that is by no means uncomplicated, but surely ground-up design is more so).
I don't think we've had the number of man-hours go into a program for the development of a first-stage liquid engine. I say this, while being very much aware of the existence of the dedicated ISRO Liquid Propulsion Systems Centre.
And if we're talking about clustered engines, IIRC, the first ever test of a clustered engine happened in 2010 (with Vikas).
It wasn't a judgment of competence. Just an assessment opinion of current capability. We'll get there. And if indeed, we're really serious about HSF, we'll get there sooner rather than later. Even though Indian astronauts training/living in B'lore might be expected to be unfazed by vibrations - given their extensive experience with potholed roads :)
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test fire is scheduled in September