In before this becomes an update thread for the day.
The Coolest Hot Engine!!!!!
OK.. so from the video, and the brochure, this is what I've managed to corral about the CUS.
Length: 8.7 m
Diameter: 2.8 m
Prop: LH2/LOX (Typical Isp of combination - 450 s
Propellant Mass: 12.8 tonnes
Max Thrust: 75 kN
Nominal thrust: 73.55 kN - including thrust from the 2 gimballed steering engines on the stage (Separate engines, or is the gas generator exhaust being used for this a la Merlin? The fact that the brochure says that the Main engine has 200s of test time and the steering has 100s makes me think these are hypergolic verniers. If it was the GG exhaust, the steering would've had ATLEAST the same run time as the main. Having said that, the animation shows a separate off axis gas generator exhaust, so that's probably used too.)
Nominal Burn time: 720 s
Cricket-stadium Isp (assuming uniform mass flow rate for 720s) : 430.2 seconds
The nozzle has a jacket for cooling, and propellant (LH2/LOX?) pre-heating. The stage also has a bell extension. Pretty standard.
Individual booster pumps for LH2 and LOX, feeding a main turbo-pump running at 40,000 rpm. Thrust control and mixture ratio control possible through two regulators.
I've got a few questions:
1) Thrust control through mixture control? As opposed to throttling both flow rates up/down proportionally to maintain optimum combustion ratio (and conserve propellant)? Does this optimum ratio change through the course of the flight (I'm thinking residual atmospheric oxygen - thinning out with height)
2) The Mahendragiri test video grabs showed a orange/red/yellow flame... Hydrogen burning produces a blue flame doesn't it - regardless
of mixture ratio? I mean it's not like there's a partial combustion product for the reaction? The flame was fidgety too.. now I'm not saying they don't have stable combustion - we might have been seeing transients - but it definitely was dancing.
3) What the heck is happening at 7:58 in the video
? Something's inflating?
4) Like most modern cryogenic stages, the LH2 tank is physically removed from the LOX tank, with an air-gap present between them. Can someone explain why? I thought the second stage of the Saturn V implemented a great solution in realising a common bulkhead (
- PS: 1:35 is AWESOME
) The video explicitly mentions it for good measure, but I would've thought anyway - that the steeper thermal gradient would've been between either fluid and the ambient air. Also surprisingly for something that's meant to be kept cool, the tanks are painted black!
5) The video showed the cryo prop-depot enclosure, but the shots of the launch pad don't seem to. How far away is it from the pad? I guess it would be desirable but is it even feasible to have a mobile cryogenic tanker? Related: has anybody here ever been to SDSC? Does ISRO conduct a guided public tour – for students/educational institutions atleast? (Or do they share Kanaka's paranoia?