For interplanetary missions to Mars, NASA has chosen Aerojet’s monopropellant hydrazine thrusters for both cruise and landing for all Mars landers to date for the simple reason that hydrazine (N2H4) does not contain carbon.
From the article:QuoteFor interplanetary missions to Mars, NASA has chosen Aerojet’s monopropellant hydrazine thrusters for both cruise and landing for all Mars landers to date for the simple reason that hydrazine (N2H4) does not contain carbon.What's wrong with carbon?
Anyway, does aerojet have any FIRM customers that have bought on to any of their new thrusters or engines for flight?
Quote from: Robotbeat on 02/07/2012 03:40 amAnyway, does aerojet have any FIRM customers that have bought on to any of their new thrusters or engines for flight?They'd need to make them first, right. And then companies don't go into sales and allow competitors know.Strange question.
Nitrous/ethanol, eh? I tried it in CEA, with a 30 bar chamber and a 100:1 nozzle, and I got a vacuum Isp of around 295-300 s, ±10 or so, with several seconds difference between room-temperature gaseous N2O and cryogenic liquid N2O. Chamber temperature is a bit shy of 3100 K. The optimum O/F ratio seems to be around 5...Overall performance might be 30-50 seconds short of optimum LOX/ethanol (>3300 K, less nitrogen).Does this sound wrong to anybody?The reason the optimum O/F is so high is probably the relatively small oxygen fraction - the nitrogen doesn't really care much about the alcohol, and there's a lot of N2 in the exhaust. But while N2O may be a fairly unenthusiastic oxidizer, it has a high positive heat of formation; cryogenic liquid N2O is a monopropellant with an Isp of about 180 s at 100:1. Room-temperature gaseous N2O does better: 200 s. In fact the article mentions work on nitrous oxide as a monopropellant...
Interesting article! The green prop part was all new to me.
http://www.nasaspaceflight.com/2012/02/aerojets-confidence-next-generation-engine-green-propellants/Mainly let the quotes do the talking in the second half, as it heady stuff All quotes to NSF via the good folks at Aerojet.
Good stuff. I like the idea of 'trying' to move away from toxic chemicals on HSF missions, especially ones of long duration. The real benefit is reduced complexity (wrt safety) on the ground with processing & handling, but you never know: in the future we may need to perform orbital repairs, and the more benign the propellants the better. Obviously a long way from that, but you have to give it a chance.
Quote from: robertross on 02/08/2012 12:15 amGood stuff. I like the idea of 'trying' to move away from toxic chemicals on HSF missions, especially ones of long duration. The real benefit is reduced complexity (wrt safety) on the ground with processing & handling, but you never know: in the future we may need to perform orbital repairs, and the more benign the propellants the better. Obviously a long way from that, but you have to give it a chance.There’s a performance benefit too. The established players are pretty comfortable with N2H4, and they’ve already paid a lot of the costs associated with its handling. Therefore, low toxicity isn’t as big a selling point as you might think. It just so happens that the green monoprops can give you biprop-like performance. That is the aspect that will really sell these systems once they are flight-ready.
I'm curious what Aerojet hopes to achieve with their NGE replacement for the RL-10? The impression I have (as an armchair scientist) is that the RL-10 is about perfection when it comes to ISP, weight and thrust-to-weight ratio. How would the NGE improve on any of that?
Quote from: beb on 02/08/2012 12:35 pmI'm curious what Aerojet hopes to achieve with their NGE replacement for the RL-10? The impression I have (as an armchair scientist) is that the RL-10 is about perfection when it comes to ISP, weight and thrust-to-weight ratio. How would the NGE improve on any of that?It improves on all three, and is a much smaller engine. I know how it does so, but I don't think the information is public. Let's just say it's a pretty clever little engine.
If it's smaller, wouldn't it also likely be cheaper?
Maybe it has to do with lack of (instrument or soil) contamination when looking for organic chemical life signs or precursors?
What's wrong with carbon?