I was a bit (pleasantly) surprised to read that the Aerojet Rocketdyne engine was used in both the Apollo Service Module, but also the Space Shuttle OMS (Orbital Manoeuvring System – the two smaller rocket engines on the rear, next to the three main engines)
The Apollo SM engine had to be absolutely reliable, as after it was used to enter the orbit of the Moon, it was the only way the astronauts had of leaving the Moon to get back to Earth.

Here

Spiny Norman said:

I was a bit (pleasantly) surprised to read that the Aerojet Rocketdyne engine was used in both the Apollo Service Module, but also the Space Shuttle OMS (Orbital Manoeuvring System – the two smaller rocket engines on the rear, next to the three main engines)
The Apollo SM engine had to be absolutely reliable, as after it was used to enter the orbit of the Moon, it was the only way the astronauts had of leaving the Moon to get back to Earth.

Here

I’ll look into this later. Very interesting.

> absolutely reliable

Well, as reliable as possible with only about 10 years of testing as a rush job. Better to say “overengineered”.

It was also used in the second stage of Delta II rockets right up until 2018.

dv said:

It was also used in the second stage of Delta II rockets right up until 2018.

Used all the way from 1958 to 2018. A sixty year lifespan.

You’d have to go to Russia to find any rocket engine with a similar lifespan. Soyuz was first launched in 1966 and is still in operation.

Interesting how relatively minor modifications allowed the use of different hypergolic binary fuels.

• UDMH and Nitric acid
• Aerozine 50 (a 1:1 mix of UDMH and hydrazine) and nitrogen tetroxide (N2O4)
• Monomethylhydrazine and nitrogen tetroxide

There’s been a trend away from hydrazine-based hypergolic fuels lately. Why? For OH&S reasons, or air pollution reasons?

The engine looks startlingly simple. No massive spaghetti of pipework that has been standard on liquid fuelled rocket engines since the V2. Compare the pipework on the AJ10 to that on the V2.