|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Improved Isp Rocketry II
Two questions this time:
1) Is it possible to get kerosene-LOX or propane-LOX to 395Isp? I've seen numbers around 360 on www.astronautix.com . 2) How effectively do large, altitude compensating nozzles (particularly aerospikes like on Bono's Rombus) maintain specific impulse between sea level launches and orbit? For example, would it be reasonable to maintain a LOX-propane specific impulse of 350 between the ground and orbit? Mike Miller, Materials Engineer |
#3
|
|||
|
|||
Improved Isp Rocketry II
(Mike Miller) :
Two questions this time: 1) Is it possible to get kerosene-LOX or propane-LOX to 395Isp? I've seen numbers around 360 on www.astronautix.com . 2) How effectively do large, altitude compensating nozzles (particularly aerospikes like on Bono's Rombus) maintain specific impulse between sea level launches and orbit? For example, would it be reasonable to maintain a LOX-propane specific impulse of 350 between the ground and orbit? Mike Miller, Materials Engineer What happened to AlH3? Earl Colby Pottinger -- I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos, SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to the time? http://webhome.idirect.com/~earlcp |
#4
|
|||
|
|||
Improved Isp Rocketry II
In article ,
Mike Miller wrote: 1) Is it possible to get kerosene-LOX or propane-LOX to 395Isp? I have my doubts, but I wouldn't call it absolutely impossible without doing some numbers. It would certainly be difficult. 2) How effectively do large, altitude compensating nozzles (particularly aerospikes like on Bono's Rombus) maintain specific impulse between sea level launches and orbit? Careful here. Altitude compensation, in principle, maintains optimal expansion regardless of outside pressure. That doesn't mean retaining the same Isp! In general, the higher the expansion ratio the higher the Isp, and if chamber pressure stays constant, an altitude-compensating nozzle has to back off on the expansion ratio when outside pressure is high. For example, would it be reasonable to maintain a LOX-propane specific impulse of 350 between the ground and orbit? Getting that sort of Isp at high altitude is not a big problem, as witness some of the Russian LOX/kerosene upper-stage engines. 350s at sea level, however, would be quite a challenge for any LOX/hydrocarbon mix. I think you'd need a very high chamber pressure indeed to get that high an expansion ratio without overexpansion and flow separation. -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
#5
|
|||
|
|||
Improved Isp Rocketry II
In article ,
Mike Miller wrote: 1) Is it possible to get kerosene-LOX or propane-LOX to 395Isp? I have my doubts, but I wouldn't call it absolutely impossible without doing some numbers. It would certainly be difficult. 2) How effectively do large, altitude compensating nozzles (particularly aerospikes like on Bono's Rombus) maintain specific impulse between sea level launches and orbit? Careful here. Altitude compensation, in principle, maintains optimal expansion regardless of outside pressure. That doesn't mean retaining the same Isp! In general, the higher the expansion ratio the higher the Isp, and if chamber pressure stays constant, an altitude-compensating nozzle has to back off on the expansion ratio when outside pressure is high. For example, would it be reasonable to maintain a LOX-propane specific impulse of 350 between the ground and orbit? Getting that sort of Isp at high altitude is not a big problem, as witness some of the Russian LOX/kerosene upper-stage engines. 350s at sea level, however, would be quite a challenge for any LOX/hydrocarbon mix. I think you'd need a very high chamber pressure indeed to get that high an expansion ratio without overexpansion and flow separation. -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
#6
|
|||
|
|||
Improved Isp Rocketry II
|
#7
|
|||
|
|||
Improved Isp Rocketry II
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Improved Specific Impulse Rocket Engines | Mike Miller | Technology | 12 | December 24th 03 06:50 AM |
Jet-fueled Rocketry | Mike Miller | Technology | 3 | October 31st 03 08:42 PM |
Spotlight: Lending an Improved Ear | Ron Baalke | Technology | 0 | September 9th 03 12:21 AM |