Very good outline Chris.Two points - 1) "Because this (booster) competition isn’t set to end until 2015, SLS teams have had to analyze both versions of the Block 1A, given the differences in their performance characteristics and environments – such as aerodynamic factors like Max Q, as well as vibration, acceleration, acoustics – thus the engineers need to ensure the core stage design is compatible with both options."That seems like backward thinking - to design something for any/all or no future options. While it's a nice ability, it doesn't seem to be a necessary one.Unless things have changed since the end of last year, ATK can support 11 launches with their current stockpile of SRBs and no recovery. Considering one launch every two years (starting with a possible hold down test in 2015), that means more/upgraded boosters won't be needed until the mid-2030's.I don't think the booster competition is needed at this time, especially with budgets/timelines as tight as they are, and in 20yrs when more/better boosters are needed the burden should fall on the competitors to match the existing vehicle.2) "The current plan is to use the (16) RS-25Ds on the (two Block 1 and) first two Block 1A flights, prior to switching to the expendable version of the engine, known as the RS-25E."i) I'm assuming the RS-25D engines used in the 2015 hold down test will be refurbished and used on one of those flights.(ii) For years I have, and still think the selection of the RS-25 is a mistake. While the heritage is there, starting RS-25E production is an entirely new engine program (To say it's a modification of an existing program is as fallacious as saying the J-2X is a modification of the J-2S program). If a new engine is the route taken, why not make the RS-25 design much simpler while adding 150,000flb -- the STME. (iii) Or even better, use an existing production line based on RS-25 heritage, one that shares cost with another launch vehicle and is even simpler still and has an additional 150,000flb -- the RS-68.(iv) A question; Are the performance figures of a possible RS-25E close enough to state?
As to the LRB competition - is it firm knowledge that only Aerojet will bid, or would an RD-180-based solution still be possible?
(iii) RS-68 has become a non-viable engine choice for SLS principally because of the use of SRB's.
Quote from: clongton on 02/24/2012 11:47 am (iii) RS-68 has become a non-viable engine choice for SLS principally because of the use of SRB's.So what if a LRB replaces the SRB ; would the RS-68 be re-considered ?
I'm thinking not. They seem very set on the RS-25s. Of course, you never know!
They seem very set on the RS-25s.
Re;A) RS-25E is not an entirely new engine program. This design has been underway for many years now and is essentially at the point where the only big change remaining is the nozzle. Even that has already been conceptually designed and awaits only the production design and tooling to be put in place to build it (big picture).B) RS-68 has become a non-viable engine choice for SLS principally because of the use of SRB's. The ablatively cooled nozzle would not survive long enough for the vehicle to reach MECO because of the thermal environment at the base of the vehicle.C) ...But the door has already been closed to that and the Air Force is not amicable to reopening it.
a) SSME, RS-25E, STME and RS-68 all spent years being designed. Two went through testing, production and flight. One no longer has a production line and the other is in production. By those measures, of the remaining two, the STME designed decades ago is as close/closer to flight than the RS-25E.b) I have and do disagree with that statement. As I could design and prototype an effective, simple solution in 60 days, I find the assertion the RS-68 is "a non-viable engine choice" to be BaselesS hand waiving. You determine the "who" and "why" for the claims.c) Would you consider the 'door closed' for a human-rated RS-68, thus the door closed on Delta IV as well? A few links/quotes;http://www.nasaspaceflight.com/2009/09/ula-claim-gap-reducing-solution-via-eelv-exploration-master-plan/In regards to the entire Delta IVH - " Numerous upgrades and modifications are listed, but also with cited uncertainty as to how many of the modifications would be required. ...Of note is that quite a few of the requirements are not driven by explicit redundancy requirements, but on other anticipated safety criteria as the desire to reduce the release of burning H2 at RS-68 start, added the paper.Also, in some cases different redundancy upgrades (RS-68 backup valves, feedline prevalves, and hydraulics redundancy) need to be traded off to find the smartest implementation path. This makes the final suite of upgrades somewhat uncertain. However, the anticipated total scope and cost of these safety upgrades is programmatically small, with engine mods the most expensive due to high intrinsic recertification cost." "http://www.floridatoday.com/content/blogs/space/EELVHumanRating.pdfPg 8/9 on RS-68 Human-Rating - "A representative list includes: 1) improving the reliability of the engine controller; 2) further evaluating and mitigating any structural margin issues that do not comply with "Strength and Life Assessment Requirements for Liquid Fueled Space Propulsion System Engines," NASA-STD-5012, 13 June 2006; 3) developing redundant actuators and valves, and installing triple-redundant sensors for more robust fault detection; 4) improving quality control to meet human-rating requirements; 5) implementing a cross-strapped pressurization system; and 6) additional qualification testing to determine reliability."
Great article Chris. My reaction is very similar to when the Ares V was being designed. Three years in and still debating what engines to use. (HLV / SLS / Orion / Constellation / Missions To Mars (HSF) / Re: Return to SSME - Ares V undergoes evaluation into potential switch) on: 12/27/2008 09:05 AM"It amazes me that Ares V has been on the drawing board for over 3 years and they don't know what engines they are going to use yet. Don't they have rocket formulas that calculate out how much thrust puts how much weight into orbit? From there they could figure out how much weight they need to launch and pick the correct engines." If they don't pick the engines and bend metal this rocket will suffer the same fate. Time and money are limited. I can't imagine an auto company designing a car this way.
This is the part that seemed similar. IMO " SLS VCR 11000 sports two solid-propellant Advanced Composite Boosters (ACBs), the same core stage as the 10000 vehicle, with a cargo adapter and fairing on top.SLS VCR 12000 is the same vehicle as the 11000, except this version would use Liquid Rocket Boosters (LRBs) instead of the ACBs. Only one version be it the 11000 or the 12000 " They are designing it for both (solid and liquid). Why not pick one and live with it. That would eliminate a lot of cost. It seems to me they are trying to please everyone and ultimately we will get nothing.
1. It's more forward thinking than backward thinking. It's looking at the entire program from a decadal pov rather than the short term. What LRB's can potentially bring to the table significantly outweigh the advantages of the SRB's, depending of course on their final design parameters, but they cannot be ready in time to drive the SLS design. So it is an appropriate decision to design the core to support either, so long as performance is not compromised by that decision, which it is not. We only want to build one core design for the entire life of the program (3 to 5 decades). We're going to be flying this vehicle for the next 30-50 years, not just 11 flights. It's far better to take the time up front to make sure we make the correct configuration choices than to succumb to we have enough SRB's for 11 flights so let's just down-select to them right away. Forget LRB's. That is short-sighted thinking.