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  [Discuss] RS-25 engines reallocated to SLS

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Author Topic:   [Discuss] RS-25 engines reallocated to SLS
Robert Pearlman
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posted 01-12-2012 08:15 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Editor's note: In an effort to keep the topic [SLS] RS-25 (SSME) engine tests (Stennis A-1) focused on status updates, readers' feedback and opinions are directed to this thread.

Please use this topic to discuss the use of RS-25(D/E) engines for the Space Launch System.

Hart Sastrowardoyo
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posted 01-12-2012 08:17 PM     Click Here to See the Profile for Hart Sastrowardoyo   Click Here to Email Hart Sastrowardoyo     Edit/Delete Message   Reply w/Quote
Will the core stage be reusable? Seems a waste to use components that are designed to be resuable - albeit with a more finite life than 55 missions they were originally expected to be used for - and throw them away after one use.

Robert Pearlman
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posted 01-13-2012 04:39 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The 15 space shuttle-used RS-25D engines will be lost with the first few test flights of the Space Launch System. The follow-on RS-25E engines will be streamlined to take into account their expendable use.

dabolton
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posted 06-09-2013 06:58 PM     Click Here to See the Profile for dabolton     Edit/Delete Message   Reply w/Quote
Why are they having to fabricate a new adaptor if the engines came from the shuttle program; what happened to the equipment used to test during the shuttle program?

Robert Pearlman
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posted 06-09-2013 07:37 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
As the space shuttle program was winding down, the A-1 test stand was modified to support testing of the J-2X engine, which will power the second stage of the Space Launch System (and was previously part of the Ares booster).

The changes were incompatible with the SSME (RS-25) engines.

The new adapter will allow testing of the RS-25 (D/E) while maintaining the J-2X hardware for future tests. This way, the A-1 stand will be able to be used for both engines, as needed.

JBoe
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posted 02-09-2014 07:47 AM     Click Here to See the Profile for JBoe   Click Here to Email JBoe     Edit/Delete Message   Reply w/Quote
When the 15/16 RS-25's become fitted and used on the SLS, will the J2X fill future SLS's or will there be a mixture of RS-25's and J2X's initially?

Robert Pearlman
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posted 02-09-2014 09:47 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The J-2X is not planned for use with the first stage of the SLS; after the stock of shuttle-legacy RS-25D engines are spent, they will be replaced with an upgraded version designed to be expendable (RS-25E).

As for the upper stage, Aviation Week reported in October 2013 that NASA no longer has an immediate need for the J-2X, which is considered overpowered for the first set of SLS planned missions.

Congress ordered an SLS able to lift 130 metric tons to low Earth orbit (LEO), which is a generally accepted requirement for launching a Mars mission. But for missions to the [vicinity of the] Moon, where a lot of Mars-precursor missions are being planned, a 105-ton SLS is probably sufficient, according to Steve Creech, May's deputy, who is responsible for finding other applications for the SLS.

One way to get to that capability would be with a "dual-use upper stage" carrying three or four RL-10s. All of them would ignite to get the payload — an Orion crew capsule, in-space habitat or lunar lander — into LEO, and then some subset of that number would fire for the trans-lunar injection to send the payload toward the Moon.

NASA hasn't ruled out using the J-2X for that portion of the trip, but it could be faster to develop the dual-use stage than the originally planned SLS upper stage powered by the J-2X, and a cryogenic propulsion stage (CPS) for getting into lunar orbit.

The RL-10 is currently used for the Centaur upper stage on the Atlas V and the second stage of the Delta IV.

Headshot
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posted 02-09-2014 12:30 PM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
Will at least one of the SSMEs be preserved for posterity, or will they all be used and discarded?

Robert Pearlman
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posted 02-09-2014 12:43 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Congress instructed NASA to use all available and applicable shuttle assets in support of the Space Launch System, and so NASA intends to use all the flight-worthy RS-25D engines it has in inventory.

That said, there are shuttle-era SSMEs already on display in museums, including at the National Air and Space Museum (in the Moving Beyond Earth gallery), at the Kennedy Space Center Visitor Complex (in the Space Shuttle Atlantis exhibit) and at Space Center Houston (to name just three, there are others).

DavidH
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posted 02-10-2014 10:15 AM     Click Here to See the Profile for DavidH   Click Here to Email DavidH     Edit/Delete Message   Reply w/Quote
As well as the U.S. Space & Rocket Center (ironically, Pathfinder has genuine engines while Atlantis, Discovery, Endeavour and Enterprise do not) and at Marshall Space Flight Center, visible on the USSRC bus tour.

Jim Behling
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posted 02-10-2014 10:43 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
Atlantis, Discovery, Endeavour have authentic and flown SSME nozzles. The powerheads, which are not visible while installed in an orbiter, were removed.

Robert Pearlman
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posted 02-10-2014 10:48 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Which, I understand, is the same for Pathfinder; only the two nozzles on Pathfinder flew on STS-1.

The displays I was referring to though are not the on the orbiters, but standalone, intact engines (though not necessarily assembled of parts that flew together on the same mission). For example, the National Air and Space Museum's SSME:

This SSME is made of up of components of SSMEs that have flown into space. The flights have included the first four Shuttle missions, the second Hubble Space Telescope repair mission, the missions that launched the Magellan and Galileo space probes, and the John Glenn flight. The engine was donated by Rocketdyne to the Smithsonian in 2004.
The California Science Center also has an SSME on display next to Endeavour.

OV3Discovery
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posted 03-17-2015 06:50 PM     Click Here to See the Profile for OV3Discovery     Edit/Delete Message   Reply w/Quote
Why was SSME chosen over the more powerful Saturn V's F-1 Rocketdyne engines for the SLS core stage?

Blackarrow
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posted 03-17-2015 06:50 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
I assume because there is a ready supply of flight-proven SSMEs and there are no F-1s available.

OV3Discovery
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posted 03-18-2015 05:30 AM     Click Here to See the Profile for OV3Discovery     Edit/Delete Message   Reply w/Quote
Well yes, we do have a steady stream of the space shuttle main engines.

Robert Pearlman
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posted 03-18-2015 05:45 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Congress directed NASA in designing the SLS that it had to incorporate existing shuttle hardware as available, hence the use of the SSMEs (RS-25) and solid rocket boosters.

Jim Behling
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posted 03-18-2015 06:30 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by OV3Discovery:
Why was SSME chosen over the more powerful Saturn V's F-1 Rocketdyne engines for the SLS core stage?
Because the F-1 would be wrong for that application. The core stage is a sustainer stage much like the Atlas of old. The SLS burns longer and at higher altitudes. The F-1 would be more suitable to replace the SRBs.
quote:
Well yes, we do have a steady stream of the space shuttle main engines.
15/16 SSME's is a steady stream since the SLS flight rate is once per year.

Paul78zephyr
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posted 08-24-2015 08:51 PM     Click Here to See the Profile for Paul78zephyr     Edit/Delete Message   Reply w/Quote
Will four RS-25D/E engines (i.e. SLS core) be tested together on B-1/B-2 test stand as five F-1 engines (S-1C) had been?

Robert Pearlman
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posted 08-24-2015 10:51 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Yes, the SLS core stage with four RS-25D engines will go through a hot fire test on the B-2 stand at Stennis.

As of two months ago, the hot fire was targeted for the fourth quarter of 2017.

Blackarrow
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posted 02-15-2016 05:30 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
How many SLS launches before NASA uses up all of the leftover shuttle engines? Are more to be built if required (say if a future President orders a "big push" into deep space)?

Editor's note: Threads merged.

Robert Pearlman
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posted 02-15-2016 05:35 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The first four missions will be flown using 16 existing shuttle engines that have been upgraded.

In November 2015, NASA signed a $1.16 billion contract with Aerojet Rocketdyne to restart development of the RS-25, including the delivery of six new flight engines and one ground certification engine by 2024, enabling a fifth flight of the SLS.

Blackarrow
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posted 02-17-2016 04:57 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
And beyond that...?

Robert Pearlman
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posted 02-17-2016 05:26 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Beyond that is to be decided based on future mission planning. First, NASA needs to get through flight testing the SLS and Orion, assuming both vehicles politically survive over the next few years.

cspg
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posted 03-11-2016 02:44 AM     Click Here to See the Profile for cspg   Click Here to Email cspg     Edit/Delete Message   Reply w/Quote
So on one hand we have SpaceX striving for reusability of its first stage, and on the other NASA which will throw away reusable engines. What am I missing? Those SSME should go into museums and used as test articles, not at the bottom of the Atlantic.

Jim Behling
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posted 03-11-2016 05:49 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by cspg:
Those SSME should go into museums...
That is the worse thing to do. Flight engines are to be used and not turned into displays. There are plenty of SSMEs in museums.

cspg
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posted 03-11-2016 07:25 AM     Click Here to See the Profile for cspg   Click Here to Email cspg     Edit/Delete Message   Reply w/Quote
Ah, ok, I agree. I didn't know (or recall) that there were SSMEs in museums! So the remaining should be on test stands.

Jim Behling
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posted 03-11-2016 03:22 PM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by cspg:
So the remaining should be on test stands.
No need for them to be on test stands, we already know how and that they work. The best thing for flight engines is to use them in flight.

Robert Pearlman
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posted 03-11-2016 03:31 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Well, they are going to be on test stands — before flying on the SLS. Whether being fired individually on the A-1 Test Stand or in groups of four installed on an SLS core on the B-2 Test Stand, the engines (at least the initial eight) are being test fired at Stennis.

Robert Pearlman
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posted 07-15-2016 08:27 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
A 650-second test fire of an RS-25 engine at Stennis Space Center on Thursday (July 14) shut down early due to a problem with the test stand.
Today at 5:57 p.m. (CST) RS-25 developmental engine number 0528 initiated a test firing. There was a minor issue with the test stand that triggered an early shutdown of the test. The test systems in place responded properly by shutting down the test in an orderly fashion.

Blackarrow
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posted 07-23-2016 09:05 AM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Robert Pearlman:
A 650-second test fire of an RS-25 engine at Stennis Space Center on Thursday (July 14) shut down early due to a problem with the test stand.

This concept always worried me. If an engine has worked perfectly on every firing so far, does another, very long, test-firing make it more likely to perform perfectly on a real flight, or might the long test-firing actually make it more likely to fail in flight?

It is well-known that athletes can "over-train." Can an otherwise-reliable engine be "over-tested"?

Paul78zephyr
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posted 09-08-2016 09:20 PM     Click Here to See the Profile for Paul78zephyr     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Robert Pearlman:
Well, they are going to be on test stands — before flying on the SLS.
Robert, can you post or link to the serial numbers for all these engines and which ones have flown on which shuttle missions, and for how many seconds have they been fired, and what is their test schedule, etc.

Also is the test firing of a SLS core stage with four RS-25 engines still on schedule for 2017?

Paul78zephyr
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posted 09-08-2016 11:39 PM     Click Here to See the Profile for Paul78zephyr     Edit/Delete Message   Reply w/Quote
Nevermind, you already did - for me - 5-1/2 years ago!

Perhaps there is an updated version of this chart with engines above 2061. ?

Now what I don't understand is there are references to engines with 05XX serial numbers (i.e. 0525, 0528) in the discussion at the link in post 1.I don't see in those serial number engines in the chart - where did those serial number engines come from?

Thanks
Paul

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