Author Topic: Aerojet Rocketdyne's AR-1 engine (aka AJ-1E6)  (Read 230037 times)

Offline Steven Pietrobon

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I think a reusable first stage using nine AR-1's would be the basis for a great launch vehicle. That would have 20.0 MN of thrust, slightly less than Falcon Heavy at 22.8 MN. A reusable upper stage using four RL-10's would could then be made.

I've also looked at replacing the SLS core and boosters with a single stage using 19 AR-1's (42.3 MN of thrust). This would have an impulse of 8.92 GNs, compared to 7.53 GNs for 2xRSRMV+Core. That might be enough to have a reusable stage. Engine configuration below.

Unfortunately, all other details on the AR-1 have not been made public, so it makes it difficult for us to estimate performance.

http://www.rocket.com/innovation/ar1-engine
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Offline 1

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Sorry Steven, am I misunderstanding something? AR-1's intended to be a dual-chambered engine as I understand it; wouldn't you need some configuration of '38 circles in a circle'? Or is each circle intended to mark engine footprint rather than nozzle footprint?

Offline Steven Pietrobon

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Sorry Steven, am I misunderstanding something? AR-1's intended to be a dual-chambered engine as I understand it; wouldn't you need some configuration of '38 circles in a circle'? Or is each circle intended to mark engine footprint rather than nozzle footprint?

The AJ1E6 was dual chamber. The AR-1 is single chamber.
« Last Edit: 04/17/2019 06:22 am by Steven Pietrobon »
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Offline GWH

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Correction to my previous post, their new AR-1 website DOES mention reusability:

Quote
AR1ís choice of propellant combination, high-performance engine cycle, and thrust-level make it an attractive propulsion solution from the Delta-II-class through EELV with potentially applications for larger, reusable launch vehicles.
http://www.rocket.com/innovation/ar1-engine

Offline 1

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Sorry Steven, am I misunderstanding something? AR-1's intended to be a dual-chambered engine as I understand it; wouldn't you need some configuration of '38 circles in a circle'? Or is each circle intended to mark engine footprint rather than nozzle footprint?

The AJ1E6 was dual chamber. The AR-1 is single chamber.

Huh, somehow I missed the memo on that (and it doesn't look to be a recent memo either). Carry on, then.

Offline john smith 19

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I think a reusable first stage using nine AR-1's would be the basis for a great launch vehicle. That would have 20.0 MN of thrust, slightly less than Falcon Heavy at 22.8 MN. A reusable upper stage using four RL-10's would could then be made.
I'm curious, given the KE and PE an upper stage has to handle would be much bigger (11.3x in the case of F9, probably a bit less if the delta v was split a bit more evenly between stages) and the payload/structure tradeoff is 1:1 on a US.

What did you have in mind?
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Offline Steven Pietrobon

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I'm curious, given the KE and PE an upper stage has to handle would be much bigger (11.3x in the case of F9, probably a bit less if the delta v was split a bit more evenly between stages) and the payload/structure tradeoff is 1:1 on a US.

What did you have in mind?

Well, I would start with a dual engine RL-10 expendable upper stage and see what performance I get to GTO, optimising the size of the first and second stage with 1.2g initial acceleration. We can then look at adding reusability to the second stage, either by an inflatable heat shield, steel tanks and tiles or a heat shield that rotates under the engines.
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Offline hkultala

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I'm curious, given the KE and PE an upper stage has to handle would be much bigger (11.3x in the case of F9, probably a bit less if the delta v was split a bit more evenly between stages) and the payload/structure tradeoff is 1:1 on a US.

What did you have in mind?

Well, I would start with a dual engine RL-10 expendable upper stage and see what performance I get to GTO, optimising the size of the first and second stage with 1.2g initial acceleration. We can then look at adding reusability to the second stage, either by an inflatable heat shield, steel tanks and tiles or a heat shield that rotates under the engines.

Dual RL-10 (only 22 tonnes of thrust) would be seriously underpowered to be used with reusable first stage; Reusable first stage would mean optimal staging point would be much lower than where Atlas V stages, meaning the second stage would practically have to contain about twice as much propellant than Centaur, meaning T/W would not increase compared to Centaur and lower staging also means same T/W gives worse gravity losses.
« Last Edit: 04/17/2019 07:49 am by hkultala »

Offline MATTBLAK

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Dr Steven; if a heavy lifter like SLS (or similar) had a pair of expendable strap on boosters, each powered by 4x AR-1s - what sort of lifting performance could we expect instead of big solids?
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Offline envy887

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Dr Steven; if a heavy lifter like SLS (or similar) had a pair of expendable strap on boosters, each powered by 4x AR-1s - what sort of lifting performance could we expect instead of big solids?

There is a small gain (on the order of 5%) but it doesn't make a significant difference without at least upgrading the upper stage to EUS, or preferably even a larger upper stage. Adding booster performance helps lift the core stage higher, but since the burnout mass of the core stage is so large (~100 tonnes) you don't want to bring it much past LEO.

A 6-engine stretched EUS would probably get a fair amount more performance for less money than liquid boosters.

Online edkyle99

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Aerojet Rocketdyne is pitching that someone could build a Delta II class rocket using a single AR-1 and single RL-10 as the upper stage. I'd assume some vernier thrusters for roll control as well.
This should outperform Delta 2 by a fair margin.  It would outperform Antares 230+, etc.  It is closer to Atlas 3B and Delta 4 Medium performance.  I figure that 9 metric tons to LEO/ISS should be possible, 8 tonnes to LEO/S, almost 4 tonnes to GTO, and nearly 3 tonnes to escape velocity.   

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Offline Zed_Noir

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Aerojet Rocketdyne is pitching that someone could build a Delta II class rocket using a single AR-1 and single RL-10 as the upper stage....

Why would anyone build a Delta II class expendable launcher today. Could see heavier and lighter payload launchers as viable not something like the Delta II. Especially not with a AR-1 and a RL-10. Which is about the launch cost of a brand new Falcon 9 by themselves.

Sadly the AR-1 is about 6 years too late in the launch market game. AJR should have developed it on their own dime before the appearance of the Raptor and BE-4. Really don't see anyone needing it for the foreseeable future.

Offline hkultala

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Aerojet Rocketdyne is pitching that someone could build a Delta II class rocket using a single AR-1 and single RL-10 as the upper stage. I'd assume some vernier thrusters for roll control as well.
This should outperform Delta 2 by a fair margin.  It would outperform Antares 230+, etc.  It is closer to Atlas 3B and Delta 4 Medium performance.  I figure that 9 metric tons to LEO/ISS should be possible, 8 tonnes to LEO/S, almost 4 tonnes to GTO, and nearly 3 tonnes to escape velocity.   

 - Ed Kyle

AR-1 has about 220 tonnes of sea level thrust. Antares and Atlas IIIB have about 380 tonnes of sea level thrust. I don't see single AR-1 outperforming those, even though it would have more efficient upper stage than antares has.
« Last Edit: 04/17/2019 07:09 pm by hkultala »

Online edkyle99

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Aerojet Rocketdyne is pitching that someone could build a Delta II class rocket using a single AR-1 and single RL-10 as the upper stage....

Why would anyone build a Delta II class expendable launcher today. Could see heavier and lighter payload launchers as viable not something like the Delta II. Especially not with a AR-1 and a RL-10. Which is about the launch cost of a brand new Falcon 9 by themselves.

Sadly the AR-1 is about 6 years too late in the launch market game. AJR should have developed it on their own dime before the appearance of the Raptor and BE-4. Really don't see anyone needing it for the foreseeable future.
GPS launch was originally contracted for $82.7 million and was expendable.  Aerojet had targeted $10-12.5 million per AR-1 and has contract for RL10 with NASA that averages $14.5 million per engine, so maybe $27 million in engines per launch, though probably more.  Still less than $82.7 million, but probably suggests a total AR1-RL10 launch vehicle cost exceeding $82.7 million.

Why a Medium ELV?  An AR1-RL10 launch vehicle would be able to loft 50 Electron's worth of payload in a single launch!  Fifty Electron launches cost $300 million!

 - Ed Kyle
« Last Edit: 04/17/2019 07:18 pm by edkyle99 »

Online edkyle99

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Aerojet Rocketdyne is pitching that someone could build a Delta II class rocket using a single AR-1 and single RL-10 as the upper stage. I'd assume some vernier thrusters for roll control as well.
This should outperform Delta 2 by a fair margin.  It would outperform Antares 230+, etc.  It is closer to Atlas 3B and Delta 4 Medium performance.  I figure that 9 metric tons to LEO/ISS should be possible, 8 tonnes to LEO/S, almost 4 tonnes to GTO, and nearly 3 tonnes to escape velocity.   

 - Ed Kyle

AR-1 has about 220 tonnes of sea level thrust. Antares and Atlas IIIB have about 380 tonnes of sea level thrust. I don't see single AR-1 outperforming those, even though it would have more efficient upper stage than antares has.
It would definitely outperform Antares 230 series to beyond-LEO missions and to higher altitude LEO missions.  Castor 30XL is OK for LEO missions, but it gets left behind by anything RL10 beyond LEO.

 - Ed Kyle
« Last Edit: 04/17/2019 07:27 pm by edkyle99 »

Offline ncb1397

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Beyond launch vehicles, isn't space force going to need engines for the fleet? ;D

Offline TrevorMonty

Aerojet Rocketdyne is pitching that someone could build a Delta II class rocket using a single AR-1 and single RL-10 as the upper stage. I'd assume some vernier thrusters for roll control as well.
This should outperform Delta 2 by a fair margin.  It would outperform Antares 230+, etc.  It is closer to Atlas 3B and Delta 4 Medium performance.  I figure that 9 metric tons to LEO/ISS should be possible, 8 tonnes to LEO/S, almost 4 tonnes to GTO, and nearly 3 tonnes to escape velocity.   

 - Ed Kyle

AR-1 has about 220 tonnes of sea level thrust. Antares and Atlas IIIB have about 380 tonnes of sea level thrust. I don't see single AR-1 outperforming those, even though it would have more efficient upper stage than antares has.
It would definitely outperform Antares 230 series to beyond-LEO missions and to higher altitude LEO missions.  Castor 30XL is OK for LEO missions, but it gets left behind by anything RL10 beyond LEO.

 - Ed Kyle
NG wont be replacing Antares with another liquid engine ELV. They will use a SRB ELV ie Omega or liquid engine (AR1)RLV.

A RLV means reduced sales of AR1 so small expensive production line.


Offline Lar

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Why a Medium ELV?  An AR1-RL10 launch vehicle would be able to loft 50 Electron's worth of payload in a single launch!  Fifty Electron launches cost $300 million!

Until you have hub and spoke[1], lofting 50 Electron payloads at once isn't really feasible... It is hard enough getting two payloads to share a ride, much less 50 primaries and 200 secondaries....

So that comparision is baseless, really. Compare costs and prices against the market leader in a segment at least kind of close to this launcher instead.

1 - which implies reusable everything, at least past LEO.
« Last Edit: 04/17/2019 09:53 pm by Lar »
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Offline GreenShrike

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AR-1 has about 220 tonnes of sea level thrust. Antares and Atlas IIIB have about 380 tonnes of sea level thrust. I don't see single AR-1 outperforming those, even though it would have more efficient upper stage than antares has.

Well, for a very rough calculation...

220 tonnes thrust with a 1.2 liftoff T/W gets you a ~175t rocket with a 9t payload.

If the first stage is 75% of the rocket (130t) and has a 0.92 propellant mass fraction (a PMF a bit worse than F9), then you have ~120.3t prop and ~10.5t structure.

Using RD-180's 311/338s ISP as a stand-in, and using the rule-of-thumb that says the average ISP over a booster flight is the Sea Level ISP + 2/3rds of the SL/Vacuum difference, gets you an average ~329s ISP over the flight.

So: 329*9.806*ln((175+9)/((175+9)-120.3))) = ~3420m/s for first stage flight.


The second stage is 25% of the rocket (~43.6t) and, if it has a .89 PMF (a bit worse than Centaur), then ~38.8t of it is prop. RL-10-C's ISP is ~450s.

So: 450*9.806*ln((43.6+9)/((43.6+9)-38.8))) = ~5900m/s for second stage flight.

Which gets you a total ~9320m/s dV, which does seem like enough to put something into LEO.

8t payload with the same parameters would get ~9600m/s.


Now, whether you can put together an exclusively Aerojet-Rocketdyne-powered medium-class launch vehicle and beat the Falcon 9 on mission cost is another story -- and F9's capability means that if your medium payload is overweight by a tonne or two, F9 should still be able to lift it.

As much as I'd like the Cyclone 4M to do well for Ukraine's sake, I'm pretty certain it's going to get creamed in the market. I don't think an AR-1/RL-10 rocket would be any cheaper.
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Offline ChrisWilson68

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Why a Medium ELV?  An AR1-RL10 launch vehicle would be able to loft 50 Electron's worth of payload in a single launch!  Fifty Electron launches cost $300 million!

That's like judging the economics of a semi truck by comparing it to a sedan while ignoring other semi trucks that already exist in the market.

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