Author Topic: Aerojet vs. Dynetics LRB's for SLS.  (Read 55889 times)

Offline Prober

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #80 on: 04/24/2014 04:54 pm »
And they can't "malfunction" inside the VAB. Malfunction means operating incorrectly and inside the VAB they are not operating at all. They are not even "functioning". They are just sitting there doing nothing.

Your story does not seem to mesh with the safety precautions taken in the VAB when dealing with solids. Perhaps the precautions were excessive, but the point remains that an element that comes pre-packaged with the propellant *and* oxidizer is always going to be more risky than one that contains neither at the time of handling.

enough :D   solids have their place, look at Orbital and their use in Antares.
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Offline RotoSequence

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #81 on: 04/24/2014 10:17 pm »
enough :D   solids have their place, look at Orbital and their use in Antares.

They provide a decent kick at a low price, and are capable of being stored in a launch ready condition for extended periods of time, but thanks to their fuel load, they're very unsafe relative to empty metal tubes. I don't think there's much good in maintaining SRBs for manned launch vehicles beyond subsidizing the solid rocket fuel industries who also supply ballistic missiles to the United States and its allies.
« Last Edit: 04/24/2014 10:22 pm by RotoSequence »

Offline TomH

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #82 on: 04/24/2014 10:33 pm »
Discussion of SRBs is OT for this thread. Please note the thread title and move the discussion to an appropriate location.

Offline a_langwich

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #83 on: 04/24/2014 11:39 pm »
I'm curious how hard Aerojet Rocketdyne is still pushing on the three options of AJ1E6, F-1B, and RS-25 rework.  The RS-25 work has money in hand and as much certainty as there can be in this industry, so I imagine it is secure.  The F-1B has risk reduction money in hand, so I imagine they are working towards those deliverables (was that a powerpack built?  just a GG? built and tested?  flow-tested or hot fired?). 

Soo...what does Aerojet Rocketdyne have for AJ1E6?  Wasn't there a risk reduction contract for it?  If so, what was the deliverable for that?  And the tanking/stage for the AJ1E6 boosters was going to be built by Aerojet?  Have they announced completed milestones for that structure like Dynetics did for the Pyrios?

I wonder what Orbital's choice of a production engine for Antares will mean for all this.  Also, though the chances of domestic RD-180 production seem to have receded for now, the RD-180 is a potential wildcard (could substitute for AJ1E6, I'd think).

Offline TomH

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #84 on: 04/25/2014 12:35 am »
There's been a pretty good bit of speculation about how AJ's purchase of Rocketdyne affects this. Some speculate one company can't have two entries; others say the F-1B is under Dynetics' control, and thus allowed as a separate entity. Dynetics has released a fair amount of publicity re. their efforts. They test fired the GG of an F-1A, but not the power pack. They've said nothing that I know of re. actually fabricating anything. AJ has said virtually nothing about anything that they've done in regard to AJ-1E6 other than giving it a name and stating the heritage engine it would be based on. I can't address Anteres. There was a thread re. using four RD-180s per booster.

This thread is specifically to address F-1B vs. AJ-1E6.

There is a dedicated thread to discuss RD-180 on SLS advanced boosters:

http://forum.nasaspaceflight.com/index.php?topic=33327.0

There is a dedicated thread to discuss all possible liquid entries for SLS advanced boosters:

http://forum.nasaspaceflight.com/index.php?topic=27714.0

There is a dedicated thread to discuss ATK Dark Knight Advanced Solids:

http://forum.nasaspaceflight.com/index.php?topic=30862.0

Offline a_langwich

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #85 on: 04/25/2014 02:04 am »
According to this, http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-339_SLS_Awards_Contract.html#.U1m8a1cXK_E

NASA awarded 3 advanced booster risk reduction contracts (at that point--one more was awarded later, listed below):  ATK; Dynetics for F-1B major components including powerpack fabrication and test, plus metallic cryo tank fabrication; and Northrop Grumman for composite cryo tanks.

According to http://www.nasa.gov/home/hqnews/2013/feb/HQ_13-054_Aerojet_SLS_Boosters.html , Aerojet got $23M to
Quote
reduce the risk and improve technical maturation of a liquid oxygen and kerosene oxidizer-rich staged-combustion engine. The company will fabricate a representative full-scale 550,000-pound thrust class main injector and thrust chamber, and prepare to conduct a number of tests measuring performance and demonstrating combustion stability.

I'm sure all this is mentioned in some thread, maybe this one though I didn't see it, but I thought it might be useful to throw it out again, with the nasa.gov references.

Aerojet tested a heritage gas generator, which I think you were indicating by saying F-1A, but not one they've built.

Would Northrop Grumman's composite cryo work figure in a separate booster bid (what engine)?  Do we know anything about the non-engine part of Aerojet's design?  I don't see a lot on Aerojet Rocketdyne's website about structures...might they contract that out to Northrop Grumman?  (Doesn't ATK do a lot of composite structures...be a prime on one contract proposal and a sub on another?)  I suppose Aerojet could use Boeing/LM/ULA production for the tank as well.
« Last Edit: 04/25/2014 02:15 am by a_langwich »

Offline TomH

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #86 on: 04/25/2014 02:55 am »
These are good questions, questions I'd like to have answered as well. Maybe something that Chris might want to pursue in an update article.

I doubt SpaceX is interested, but a Raptor entry would be interesting. It could at least give them some extra research money.

Offline Lobo

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #87 on: 04/25/2014 05:45 pm »
These are good questions, questions I'd like to have answered as well. Maybe something that Chris might want to pursue in an update article.

I doubt SpaceX is interested, but a Raptor entry would be interesting. It could at least give them some extra research money.

Yea, on one hand, SpaceX could get that extra R&D money from a Raptor based SLS booster contract.

On the other hand, although they won't say it, I'm sure Elon is hoping his Raptor powered BFR being available and relatively inexpensive may help cause SLS cancellation.  So probably counter productive to present a proposal for SLS that helps it's cost and performance.  I think rather than wanting a piece of the pie...they are shooting for the -whole- pie.

My guess is the latter, so I'd be surpised if Elon starts making noise about wanting to enter the booster competition.  Even though he is developing an engine that would be great for it. 

Offline baldusi

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #88 on: 04/25/2014 08:06 pm »
Look. SpaceX has two cards that depend on demonstrating usability. The big one is designing a reusable BFR and thus making SLS obsolete after the four initial launches. But the second is very interesting anyways. It would seem that Falcon Heavy inaugural flight will demonstrate something about returnable boosters. Thus, they could enter the full competition with the ace of spades. Demonstrated reusable technology. And their Raptor demonstration might even go in that direction. But knowing SpaceX, they would only do that if they kept all the ownership on the boosters.
But let's be frank, if SpaceX demonstrates just reusable boosters, the Advanced Booster competition will have a taste of obsolete.

Offline TomH

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #89 on: 04/25/2014 09:55 pm »
But let's be frank, if SpaceX demonstrates just reusable boosters, the Advanced Booster competition will have a taste of obsolete.

There is one reason I doubt Raptor boosters could be used on SLS: ISP Density of CH4 in relation to VAB door width. With the core having only 4 main engines, and with EUS being smaller than the J-2X LUS, the difference in the 130mt payload must come from potent boosters. 5.5m is the max width for boosters in relation to the VAB doors. I don't know if that volume of CH4 at its ISP density would be enough total thrust. Then subtract prop needed for RTLS, and 130mt seems exceedingly difficult.

Look. SpaceX has two cards that depend on demonstrating usability. The big one is designing a reusable BFR and thus making SLS obsolete after the four initial launches.

Agreed. Which would mean that the program failed not for the reasons so many critics posit, but because superior technology was developed by someone else and thus the fabled heritage technology was swept away by the tide of progress. I would not at all be surprised if your scenario is exactly the way history unfolds.

Offline baldusi

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #90 on: 04/25/2014 10:16 pm »
isp density is an idiotic measure. You care about pmf, isp and T/W. Your performance is not a straight multiplication. And then you have to measure it within the SLS performance requirements. Having great T/W of the stack is the important part, since the core is very efficient. It's true that the width is a limitation, not so much height. And you can look at the Dynetic proposal that's very T/W positive with moderate isp, vs the Aerojet with great isp and reasonable T/W. SpaceX could put three Raptors and have excellent isp and T/W, and then compensate with the re-usability margins. In any case, offering a reusable booster that reduces launch cost by 20% (or whatever the boosters cost to an SLS launch) and probably very low development cost, could well make the difference.

Offline Lobo

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #91 on: 04/25/2014 11:02 pm »

There is one reason I doubt Raptor boosters could be used on SLS: ISP Density of CH4 in relation to VAB door width. With the core having only 4 main engines, and with EUS being smaller than the J-2X LUS, the difference in the 130mt payload must come from potent boosters. 5.5m is the max width for boosters in relation to the VAB doors. I don't know if that volume of CH4 at its ISP density would be enough total thrust. Then subtract prop needed for RTLS, and 130mt seems exceedingly difficult.


CH4 is only like 19% less dense than RP-1, and that applies to only the fuel tank.  The LOX tank would be the same size.  It could just be a little longer, use common bulkhead and still be 5.5m wide.  I don't think there'd be any problem there. 
Also, if comparing to the Pryios boosters, the difference would even be less than 19% because the high ISP Raptors need less fuel and oxydizer to get the same performance.  I would think an Adavnced booster with 3 Raptor engines would be a little longer than an Aerojet booster, but pretty close in length to the Pyrios booster.

As for extra fuel for RTLS, there's no current Advanced booster requirement for reuse, so a SpaceX entry wouldn't -need- that.  If the advanced booster soliticitation eventually included reusability, then all entrants would need more fuel, not just SpaceX.  They could offer a RTLS booster as a means of getting a really low price.  But then they'd run into issues of how to land it.  F9 has 9 engines with a central one.  One would assume BFR would have a similar configuration for Raptors and perform in the same way.  If you have a MLV size booster, with 3 Raptors, how do you land it?  A "Mini-Raptor" in the middle or something, but there'd have to be such an engine developed, and so far SpaceX hasn't indicated that's the case.  So not sure how they'd approach a reusable booster.


Agreed. Which would mean that the program failed not for the reasons so many critics posit, but because superior technology was developed by someone else and thus the fabled heritage technology was swept away by the tide of progress. I would not at all be surprised if your scenario is exactly the way history unfolds.

Elon will never say it because he doesn't want to make any enemies in Congress or NASA, but there's no way he isn't ultimately angling for that.  How could you not if you were going to build a HLV in the same class (initially) as SLS?
The officially line is their BFR is going to Mars and NOT to compete with SLS.  And they won't deviate from that...until it's time to.

And that's why I would anticipate SpaceX does not pursue the Advanced booster competition.
Besides, they'd have to come up with a new 5.5m core diameter tooling, that won't help with their Falcon or BFR LV's.  So also not much incentive there to jump in and possibly help SLS survive longer.

Edited: to correct the referenced quotes.
« Last Edit: 04/25/2014 11:44 pm by Lobo »

Offline Steven Pietrobon

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #92 on: 04/28/2014 07:37 am »
CH4 is only like 19% less dense than RP-1, and that applies to only the fuel tank.  The LOX tank would be the same size.

LCH4 has a density of 0.4239 kg/L while RP-1 has a density of 0.8 kg/L. Thus, LCH4 is 47% less dense than RP-1. However, methalox at a 3.6 to 1 oxidiser to fuel mixture ratio (MR) is 19% less dense than kerolox at a 2.8 MR.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline baldusi

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #93 on: 04/28/2014 04:00 pm »

CH4 is only like 19% less dense than RP-1, and that applies to only the fuel tank.  The LOX tank would be the same size.

LCH4 has a density of 0.4239 kg/L while RP-1 has a density of 0.8 kg/L. Thus, LCH4 is 47% less dense than RP-1. However, methalox at a 3.6 to 1 oxidiser to fuel mixture ratio (MR) is 19% less dense than kerolox at a 2.8 MR.
Rule of thumb, for staged combustion, CH4 requires 30% more volume than RP-1. Which if you scale a tank in 3D mean an 9% longer dimensions. And the general 10extra seconds or so of isp usually mean very similar performance. Of course Russians and SpaceX appear to calculate that if you design the SC CH4 cycle taking advantage of the characteristics, like using the expander cycle for something, and thinking in terms of reusability, the CH4 is superior.
BTW rocket engine with more restarts lowers development and certifications cost. You might need as little a 10 engines for development vs 100s.

Offline Lobo

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #94 on: 04/28/2014 04:34 pm »
CH4 is only like 19% less dense than RP-1, and that applies to only the fuel tank.  The LOX tank would be the same size.

LCH4 has a density of 0.4239 kg/L while RP-1 has a density of 0.8 kg/L. Thus, LCH4 is 47% less dense than RP-1. However, methalox at a 3.6 to 1 oxidiser to fuel mixture ratio (MR) is 19% less dense than kerolox at a 2.8 MR.

Ok, thanks for the clarification Steve.  I used your number of 19%, but didn't realize you meant total comparitive propellant volume, and not just the fuel comparitive volume.

Offline Lobo

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #95 on: 04/28/2014 04:37 pm »

CH4 is only like 19% less dense than RP-1, and that applies to only the fuel tank.  The LOX tank would be the same size.

LCH4 has a density of 0.4239 kg/L while RP-1 has a density of 0.8 kg/L. Thus, LCH4 is 47% less dense than RP-1. However, methalox at a 3.6 to 1 oxidiser to fuel mixture ratio (MR) is 19% less dense than kerolox at a 2.8 MR.
Rule of thumb, for staged combustion, CH4 requires 30% more volume than RP-1. Which if you scale a tank in 3D mean an 9% longer dimensions. And the general 10extra seconds or so of isp usually mean very similar performance. Of course Russians and SpaceX appear to calculate that if you design the SC CH4 cycle taking advantage of the characteristics, like using the expander cycle for something, and thinking in terms of reusability, the CH4 is superior.
BTW rocket engine with more restarts lowers development and certifications cost. You might need as little a 10 engines for development vs 100s.

Interesting.  So do you mean a Raptor methalox booster would be about 9% longer than a comparitive RP-1 staged combustion booster like an RD-180 powered booster or an AJ-1E6 powered booster?  Or that given Raptor's extra performance, it would mean the boosters would be similar in size?

Also, roughly, assuming 5.5m diameter for both, how would a Raptor powered booster compare lengthwise to the Dynetics F-1B booster?

Offline baldusi

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #96 on: 04/29/2014 03:02 am »

Interesting.  So do you mean a Raptor methalox booster would be about 9% longer than a comparitive RP-1 staged combustion booster like an RD-180 powered booster or an AJ-1E6 powered booster?  Or that given Raptor's extra performance, it would mean the boosters would be similar in size?

Also, roughly, assuming 5.5m diameter for both, how would a Raptor powered booster compare lengthwise to the Dynetics F-1B booster?
They are width limited with SLS boosters, so it would need 30% extra length to have the same propellant mass. But, this is a booster application. You need to analyze the whole stack. SLS core has amazing propulsion, but the pmf might not be that good at first. You only care about the whole stack T/W, but it might have maximum G limitations (STS was <= 3G).
But in general, NASA is very cautious wrt staged combustion engines. And those are usually more expensive. What I mean is that the F-1B is less efficient than a SC engine, but can have more thrust.

Offline TomH

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Re: Aerojet vs. Dynetics LRB's for SLS.
« Reply #97 on: 04/30/2014 10:30 pm »
What I mean is that the F-1B is less efficient than a SC engine, but can have more thrust.

Maybe our primary two mertric should be $/newton and $/Kg to destination (LEO/GSO/TLI/TMI).

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