Author Topic: Aerojet Rocketdyne's AR-1 engine (aka AJ-1E6)  (Read 255650 times)

Offline PahTo

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Predict that lobbyists will speak of a "backup engine" for Atlas V as a means to keep funding AR-1 after a BE-4 selection. That vision dies hard.
Or NASA keeping it alive as an SLS Block 2 booster engine option.

 - Ed Kyle

Yep, Ed nailed it.  Even though solids have a leg up for SLS advanced booster, and despite the fact said booster is unlikely to ever fly, I imagine funds will be made available to continue development of AR-1.

Offline Coastal Ron

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Predict that lobbyists will speak of a "backup engine" for Atlas V as a means to keep funding AR-1 after a BE-4 selection. That vision dies hard.
Or NASA keeping it alive as an SLS Block 2 booster engine option.

ULA has to end Atlas V because it's not competitive price-wise, nor can it carry the largest payloads for the USAF. So it has to die in order for ULA to live.

Which means the RP-1/LOX fueled AR-1 engine only has the option of being a "backup engine" for a liquid methane/LOX designed Vulcan or a LH2/LOX designed SLS.

I don't see a path to success there...
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline oldAtlas_Eguy

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If AR-1 has any plans for use on a liquid booster for SLS, NASA would have to find funds to support it's development. The AF would no longer do so since it would no longer have a NSS role.

The save it for use on Atlas V is not an  option because it would take the AF to fund the Atlas V redesign in order to mount the AR-1 on it, as well as pad mods and tooling etc. A significant amount of funds that would result in a new rocket that has to go through qualification and then the 3 flight success for certification to take DOD payloads all at 2 years behind the Vulcan, a few $100's million if not billion AF expense.

But all those who predict gloom and doom for AJR, that is far from the truth. AJR is more than just a few liquid rocket engines. Their main income comes from SRMs for munitions and rockets used by fielded systems which are expended regularly and are in significant production and will remain that way for years. There are other small engines RCS thrusters etc that they also manufacture for use in sats that are also likely to remain in production.

AR-1 is but a small development program in a large company.

Added: NOTE - the Vulcan with BE-4 being 2 years ahead of any use on Atlas V would basically put the Vulcan into flight tests by the time that a Atlas V with AR-1 redesign would go through a CDR. It is just too far out in time to be a program that will continue past this year unless BE-4 has some sort of sever engine design problem which this test shows that is now an unlikely occurrence. But we await the BE-4 full thrust full duration burn before the fait of AR-1 is sealed. Which would definitely occur before the end of this FY2018 and possibly even before the end of this CY2017.
« Last Edit: 10/20/2017 04:29 pm by oldAtlas_Eguy »

Offline Darkseraph

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It's premature to call the BE-4 test the end of AR-1. Aerojet Rocketdyne have quite a bit of lobbying power and even if it is not picked by ULA for Vulcan, it may end up being kept alive regardless.The effectively got SSME into use for both SLS and XS-1. AR-1 could end up being kept for a future SLS advanced engine contract. Congress may even hatch a plan to mandate integration of AR-1 with the existing Atlas V booster regardless of Vulcan using BE-4. As ridiculous as that sounds, it's not beyond them.

There is also the remote possiblity another company that wants to enter the launch market with an RLV picks it up. Large reusable ORSC engines are expensive and take years to develop. Buying from AJR would cut costs, risk and schedule enormously. DC-X which is forefunner of many RLVs today, used plain old RL-10s rather than develop brand new engines.
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

Offline Space Ghost 1962

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Predict that lobbyists will speak of a "backup engine" for Atlas V as a means to keep funding AR-1 after a BE-4 selection. That vision dies hard.
For that to be even viable AR-1 will have to switch to burning methane instead of RP-1.
Not what I was referring to.

Yes, you could retarget AR-1 to being a backup engine to Vulcan. Was referring to instead how members of Congress were being lobbied that AR-1 was a "drop in replacement" for RD180, and (in effect we're back to having someone if not ULA) revise Atlas V and keep it flying as backup, thus "backup engine" (according to lobbyist talk, not me).

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You can do dual development work for the core, based on 2 different propellants, for only so long. Right up to CDR. After that, all bets are on a single propellant. And that will be methane. And with it, the "backup" role for AR-1 goes away. Quickly IMO.
Agreed. Another possibility but not likely.

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But I agree that won't stop Aerojet-Rocketdyne lobbyists from keeping the pressure on certain folks in US Congress. After all, government funding is their bread-and-butter.
Its what they are best at, unfortunately, as a "corporation".  ::)

Which, of course, is the best combination on this planet right now.

This needs to be said now (and quickly)... the 'industry leader' is in third place in head-to-head competition.
Soon -- five years from now -- they might not have a single vehicle flying their engines.
One word: RL10


It will still be around five years from now.
RL10 is a hard, established, engine to beat. Costly too, although that doesn't need to be.

Its history is intertwined with the entire space program, even in various other countries.

However if AJR were to become a single product company, that would be ... difficult.

Predict that lobbyists will speak of a "backup engine" for Atlas V as a means to keep funding AR-1 after a BE-4 selection. That vision dies hard.
Or NASA keeping it alive as an SLS Block 2 booster engine option.

 - Ed Kyle

Yep, Ed nailed it.  Even though solids have a leg up for SLS advanced booster, and despite the fact said booster is unlikely to ever fly, I imagine funds will be made available to continue development of AR-1.
Almost brought this up.

But in Congress it could be heard things like "SLS day without solids is like a day without sunshine" (intentional pun with Florida reference), meaning it'll never see the light of day. Which is ironic given that the best chance of SLS being useful/"not cancelled" is to grow, and the limits of the scalability of the solids are the primary limitation, so for AJR to "win" OA would have to "lose".

(Note also that the F1-B work  on SLS LRE advanced boosters is still there by Dynetics, who have been brought in by AJR to "save" AR-1.)

And for those who'll attempt to bring it up also, yes you could power Antares, but again cheaper, available RD-181's are already in use (sorta ... we're coming up on its second flight). It is unclear with Northrup Grumman acquisition of OA if continuing Antares (or any launch systems) long term is desirable ... they might just fly out the CRS contract and/or switch to Atlas for the remainder.

So there are a lot of "sock puppets" to use here, but most of them have some pretty gaping holes.

Which is not surprising that AJR would desire to "get" Atlas V as a LV to operate, to transform itself into a provider, but the lobbyists can't help there, as AJR debt/stock isn't interesting, and one of Vulcan's biggest competitors for non NSS launches would then be an AJR LV - why breed your own competition. (Or in terms of Sowers, let a parasite take you over in full...)

If AR-1 has any plans for use on a liquid booster for SLS, NASA would have to find funds to support it's development. The AF would no longer do so since it would no longer have a NSS role.
Except as filling out a suite of propulsion options, which is lame but look at Raptor funding. Lobbyists think this way.

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The save it for use on Atlas V is not an  option because it would take the AF to fund the Atlas V redesign in order to mount the AR-1 on it, as well as pad mods and tooling etc. A significant amount of funds that would result in a new rocket that has to go through qualification and then the 3 flight success for certification to take DOD payloads all at 2 years behind the Vulcan, a few $100's million if not billion AF expense.

AJR says "minor changes', and the existing pads works fine. Remember, Atlas/Vulcan will share a pad.  They'd bill it as just continuing Atlas flyout past RD180, and milk Congress for billions to continue operations as a gradual phase over.  What they'll say.

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But all those who predict gloom and doom for AJR, that is far from the truth. AJR is more than just a few liquid rocket engines. Their main income comes from SRMs for munitions and rockets used by fielded systems which are expended regularly and are in significant production and will remain that way for years. There are other small engines RCS thrusters etc that they also manufacture for use in sats that are also likely to remain in production.
True but all products are under attack from rivals too. AJR has perpetual baggage, and I've been fooled too many times by the cartoonish "this time for sure" management speak.

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AR-1 is but a small development program in a large company.
Yes but billed as the pivot to turnaround AJR for more than a half decade.

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Added: NOTE - the Vulcan with BE-4 being 2 years ahead of any use on Atlas V would basically put the Vulcan into flight tests by the time that a Atlas V with AR-1 redesign would go through a CDR.
Don't discount the long fly out of Atlas. And something close to Atlas as a continuation beyond RD180 is what Congress wants more than Vulcan.

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It is just too far out in time to be a program that will continue past this year unless BE-4 has some sort of sever engine design problem which this test shows that is now an unlikely occurrence.
I'll give you a "cup of coffee" bet that it'll continue past FY2018 (redeemable eventually in Lompoc or Cocoa Beach or Denver). Not that it should.

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But we await the BE-4 full thrust full duration burn before the fait of AR-1 is sealed. Which would definitely occur before the end of this FY2018 and possibly even before the end of this CY2017.
I think it's duration and combustion stability that are the long poles. Agree with the CY2017.

Offline DreamyPickle

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One word: RL10

It will still be around five years from now.
It's not very likely but it might not survive either. Delta IV is already being discontinued and ULA could pick BE-3 for ACES. The remaining user is SLS which could also get cancelled.

Offline Space Ghost 1962

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One word: RL10

It will still be around five years from now.
It's not very likely but it might not survive either. Delta IV is already being discontinued and ULA could pick BE-3 for ACES. The remaining user is SLS which could also get cancelled.
Underestimates the fundamental effectiveness of the RL10.

It may fly in other ways for many decades. BTW Centaur advantages as well like this.

Offline Lars-J

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One word: RL10

It will still be around five years from now.
It's not very likely but it might not survive either. Delta IV is already being discontinued and ULA could pick BE-3 for ACES. The remaining user is SLS which could also get cancelled.
Underestimates the fundamental effectiveness of the RL10.

It may fly in other ways for many decades. BTW Centaur advantages as well like this.

It might or it might not. But costs matter, now more than ever. It is only recently that the industry has broken out of the "isp at any cost" mentality - we even have GTO missions done with RP-1 stages (gasp!). Two new launch vehicles are being developed with MethaLox upper stages. None of them will have engines that match the isp of RL-10, but they could still kill it off.

Offline TrevorMonty

AJR have been working on reducing RL10 build cost by redesign it to enable use of modern manufacturing technology. I think it is still ULA preferred engine but having BE3U as option helps keep AJR on their toes.

Its in AJR best interest to bring price down so ULA can stay competitive. Less ULA flys the less engines they buy.

Offline spacenut

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I would love to see boosters for SLS with 6 AR-1's on each booster with say a Merlin in the middle and NASA learn how to land the boosters.  Then SLS would be a more capable rocket and save money with reuse of the boosters. 

Offline Patchouli

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Added: NOTE - the Vulcan with BE-4 being 2 years ahead of any use on Atlas V would basically put the Vulcan into flight tests by the time that a Atlas V with AR-1 redesign would go through a CDR. It is just too far out in time to be a program that will continue past this year unless BE-4 has some sort of sever engine design problem which this test shows that is now an unlikely occurrence. But we await the BE-4 full thrust full duration burn before the fait of AR-1 is sealed. Which would definitely occur before the end of this FY2018 and possibly even before the end of this CY2017.

I thought the AR-1 was supposed to be largely a drop in replacement for the RD-180 requiring little in the way of changes to Atlas V CCB.

AJR have been working on reducing RL10 build cost by redesign it to enable use of modern manufacturing technology. I think it is still ULA preferred engine but having BE3U as option helps keep AJR on their toes.

Its in AJR best interest to bring price down so ULA can stay competitive. Less ULA flys the less engines they buy.


Moving the RL-10 to more automated construction even channel wall construction would be a step in the right direction.

I would love to see boosters for SLS with 6 AR-1's on each booster with say a Merlin in the middle and NASA learn how to land the boosters.  Then SLS would be a more capable rocket and save money with reuse of the boosters. 


That actually might be a good idea even with reuse of the booster it probably would increase the payload 10 to 30%.
Another benefit you get the first stage of a CLV in the deal by putting the old Ares I upper stage on top of it.
Though the better first stage would make the J-2X unnecessary it probably could get by with 2 BE-3Us.
« Last Edit: 10/20/2017 09:08 pm by Patchouli »

Offline oldAtlas_Eguy

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Added: NOTE - the Vulcan with BE-4 being 2 years ahead of any use on Atlas V would basically put the Vulcan into flight tests by the time that a Atlas V with AR-1 redesign would go through a CDR. It is just too far out in time to be a program that will continue past this year unless BE-4 has some sort of sever engine design problem which this test shows that is now an unlikely occurrence. But we await the BE-4 full thrust full duration burn before the fait of AR-1 is sealed. Which would definitely occur before the end of this FY2018 and possibly even before the end of this CY2017.

I thought the AR-1 was supposed to be largely a drop in replacement for the RD-180 requiring little in the way of changes to Atlas V CCB.

The engines are completely different. The RD180 is a single engine with dual TC which will be replaced by a pair of independent engines. The thrust structure, piping, software, and a lot of other items all in the same area is 100% different. Nothing is common. This is not an engine upgrade by a higher thrust version of engine in same family with similar thrust and piping connections, controllers, and software. Also the mixture ratio is different meaning the placement of where the dome separating the LOX and RP-1 tanks has to be moved creating a new tank design which must be structurally qualified. Basically you end with a nearly completely new booster.

Offline Lars-J

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Added: NOTE - the Vulcan with BE-4 being 2 years ahead of any use on Atlas V would basically put the Vulcan into flight tests by the time that a Atlas V with AR-1 redesign would go through a CDR. It is just too far out in time to be a program that will continue past this year unless BE-4 has some sort of sever engine design problem which this test shows that is now an unlikely occurrence. But we await the BE-4 full thrust full duration burn before the fait of AR-1 is sealed. Which would definitely occur before the end of this FY2018 and possibly even before the end of this CY2017.

I thought the AR-1 was supposed to be largely a drop in replacement for the RD-180 requiring little in the way of changes to Atlas V CCB.

The engines are completely different. The RD180 is a single engine with dual TC which will be replaced by a pair of independent engines. The thrust structure, piping, software, and a lot of other items all in the same area is 100% different. Nothing is common. This is not an engine upgrade by a higher thrust version of engine in same family with similar thrust and piping connections, controllers, and software. Also the mixture ratio is different meaning the placement of where the dome separating the LOX and RP-1 tanks has to be moved creating a new tank design which must be structurally qualified. Basically you end with a nearly completely new booster.

In addition, people are treating AR-1 as a "sure thing". I'm not. They have years of work remaining that would be very challenging even if they were to be selected right now by ULA.

Offline brickmack

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Didn't Aerojet claim they could completely replicate RD-180s plumbing and structural interfaces? Software interfaces shouldn't be any different (vehicle-level avionics don't care whats going on in the engine controller, all the need is a set of defined inputs and outputs with defined formats to the engine. No different from how that would be defined in any new engine early in development). Presumably when you're designing a new engine from scratch specifically to fit an existing rocket, its not infeasible to match that sort of stuff, the way it would be to adapt Atlas to use Merlin (a much more radically different engine which was developed without any concern for existing interfaces on Atlas).

Big issue I think would be taking full advantage of the increased maximum thrust, which needs a stronger thrust structure and stretched tanks and new SRBs (because Atlas V has its SRBs attaching at the intertank, which would now be higher, and that means a complete booster redesign). But couldn't they do something like Antares 200, where they keep the tanks identical to the previous version and not fully-fuel the tanks (because of the slightly different mix ratio), and run the engine at a lower max thrust? Performance would be similar-ish or maybe even slightly improved (as was the case with Antares 200, the mass ratio loss is very small and theres a slight ISP gain), just not to its full potential. They've done/will soon do comparably large modifications on Atlas and Delta anyway (RS-68A, GEM-63, RL10C, composite AV 400 fairing). Then follow it up a few years later with a completely new rocket making full use of its capabilities.

But of course its a moot point, since BE-4 is still more capable, cheaper, and coming much sooner, and obviously that would be the preferred path forward for ULA even if AR-1 was a perfect drop in
« Last Edit: 10/20/2017 09:50 pm by brickmack »

Offline Lars-J

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Didn't Aerojet claim they could completely replicate RD-180s plumbing and structural interfaces?

AJR has claimed a *lot* of things with regards to the RD-180, including being able to build a domestic copy. Yeah, we know what happened to that. Which is why I'm skeptical about the AR-1.

Offline oldAtlas_Eguy

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The basic point where if both a Vulcan BE-4 based and a Atlas V RD-180 or AR-1 exist at the same time the primary item is that if the government is given the choice between these two certified vehicles that have to fly off the same pad. That the AF will go with the lower cost booster which will be the Vulcan because it is being designed to be lower cost that the Atlas V and in a head to head would be cheaper even for the lightest payloads.

If Vulcan can not achieve this goal of cheaper than Atlas V then it will likely have a short life in this LV supply competitive environment that will be in place in the 2020's. If that happens then ULA will not live long past that point. ULA must become at least token competitive in the US with the other major US medium/heavy LV providers SpaceX, BO, and even Orbital ATK.

In order to do that they have to reduce the cost of launch. Use of an AR-1 on a Atlas V does not do that.

Offline butters

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RL-10 is their only large liquid engine with a plausible long-term future, after Delta and SLS wind down. The question is whether any amount of 3D printed RL-10 parts can overcome the amortized fixed costs of a vast enterprise which may have been reduced to selling half a dozen RL-10s per year (at best) for the remaining ULA missions not taken over by SpaceX. That's assuming ULA doesn't go with BE-3U.

Offline Coastal Ron

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It's premature to call the BE-4 test the end of AR-1. Aerojet Rocketdyne have quite a bit of lobbying power and even if it is not picked by ULA for Vulcan, it may end up being kept alive regardless.

Just as a reminder though, ULA (i.e. Boeing and Lockheed Martin) own the decision about what engine to use. It would be highly unusual for Congress to step in and mandate a business decision for a contractor.

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Congress may even hatch a plan to mandate integration of AR-1 with the existing Atlas V booster regardless of Vulcan using BE-4. As ridiculous as that sounds, it's not beyond them.

The owners of ULA are Lockheed Martin and Boeing, the two largest government contractors - who no doubt have their own large armies of lobbyists. If they don't want it to happen it likely won't.

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There is also the remote possiblity another company that wants to enter the launch market with an RLV picks it up.

I'm sure AJR will welcome them with open arms. Highly unlikely though, isn't?

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Large reusable ORSC engines are expensive and take years to develop. Buying from AJR would cut costs, risk and schedule enormously. DC-X which is forefunner of many RLVs today, used plain old RL-10s rather than develop brand new engines.

The amount of money spent on something has no relationship to how long it should survive in the marketplace. And if the marketplace does move to reusable launchers, then engines that enable that are what AJR should really be focused on if they want to stay in the rocket supplier business.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline AncientU

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Predict that lobbyists will speak of a "backup engine" for Atlas V as a means to keep funding AR-1 after a BE-4 selection. That vision dies hard.
Or NASA keeping it alive as an SLS Block 2 booster engine option.

 - Ed Kyle

Yep, Ed nailed it.  Even though solids have a leg up for SLS advanced booster, and despite the fact said booster is unlikely to ever fly, I imagine funds will be made available to continue development of AR-1.

Continuing to develop an engine (AR-1 or its variants have been around developing for 15-20 ? years) is different than anyone buying it for their operational launch vehicle.  In a cost-competitive launch services market, AJR is simply not a player.
"If we shared everything [we are working on] people would think we are insane!"
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Offline Darkseraph

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I'm sure AJR will welcome them with open arms. Highly unlikely though, isn't?
Yup. Hence I qualified it with the word 'remote', as unlikely but not zero.


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The amount of money spent on something has no relationship to how long it should survive in the marketplace. And if the marketplace does move to reusable launchers, then engines that enable that are what AJR should really be focused on if they want to stay in the rocket supplier business.
Never actually said there is a relationship between the money spent on a system and its marketplace viability. However, AR-1 already is a reusable engine and the government have effectively paid for it. Since engines like this can take up to 7 years to develop at a cost of hundreds of millions, a new entrant to the RLV market could choose to avoid those costs by purchasing something commercial and off the shelf at its marginal cost instead of reinventing the wheel. They could then focus their limited resources on all other parts of the RLV and field it sooner than would be otherwise possible. Another company attempting to compete with Blue Origin and SpaceX in the RLV market could make themselves more competitive by exactly the money and time they did not spend on something!. I've no idea how likely this scenario is with the AR-1 in particular, but it's perfectly plausible.
« Last Edit: 10/21/2017 12:21 am by Darkseraph »
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

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