Replica engines recommended for retired orbiters – Flown SSMEs for HLV

by Chris Bergin

All three orbiters are set to donate their Space Shuttle Main Engines (SSMEs) to the Heavy Lift Launch Vehicle (HLV) program, following their final flights. A Program Requirements Control Board (PRCB) meeting recommended the orbiters should instead gain Replica Shuttle Main Engines (RSMEs) – previously scrapped nozzles installed via an adaptor – for when the vehicles retire to exhibitions.


The additional nine SSMEs will boost the development program for the HLV – which is set to be Shuttle Derived (SD) – allowing them to participate in early testing and the opening test flights of the new vehicle.

The PRCB meeting – conducted on Thursday – was presented with a Change Request (CR) document, which follows on from January’s proposal to delay the disposal of SSME assets, pending “future launch vehicle architecture” decisions.

The CR presentation (available on L2) notes direction from the Space Shuttle Program (SSP) to roadmap the ability to keep the engines, and replace them with replicas for when the retired vehicles go on display at their exhibitions.

“Directed by SSP to prepare an integrated approach for an alternative to using flight Space Shuttle Main Engines (SSMEs) on post SSP orbiter displays. To obtain authorization and funding to design, build, deliver, and install nine (9) Replica Shuttle Main Engines (RSMEs) to replace flight SSMEs on orbiters,” noted the presentation.

“To preserve the SSME flight engines for future use, NASA MSFC (Marshall Space Flight Center) / KSC (Kennedy Space Center) / JSC (Johnson Space Center) recommends a replica engine be provided utilizing existing inoperable nozzle assets and an adapter to simulate the SSME for display purposes.”

SSME contractor Pratt & Whitney Rocketdyne (PWR) have already developed an integrated RSME Requirements Document and will design, manufacture, repair and provide nine RSME kits upon final approval.

While a flight ready SSME consists of large amounts of plumbing, turbopumps and electronics, etc. The RSMEs will simply consist of a scrap – but cosmetically repaired – nozzle, with an adaptor to install it into the aft of the retired orbiter.

Such installation would take place at KSC, prior to the orbiters being ferried to their final resting place.

“Nozzle Repair: Nine inoperable Nozzle’s identified to support RSME. Nozzles require cosmetic and structural repairs to forward manifold adapter attach point, aft manifold and heat shield clips,” added the presentation.

“Adapter Design: MSFC PWR will approve and control the RSME Requirements Summary Document after NASA concurrence. Baseline planned for NLT (No Later Than) 11/01/2010. RSME will comply with applicable vehicle requirements (structural interfaces only, no propellant, hydraulic, pneumatic or electrical interfaces) and applicable requirements.

“RSME nozzle adapter will be designed using Boeing Dynamic Load Criteria for ferry flight. JSC certification concurrence requested NLT 11/23/2010. RSME will be non-flight type simulator configuration (ferry flight only) hardware.

“RSME Assembly / Kit: Existing thermography adapter proof test fixture and SSME test weights will be utilized. RSME assembly / kitting will be performed at KSC in the SSMEPF (Space Shuttle Main Engine Processing Facility.”

The presentation also notes the first three RSMEs will be available as soon as April of next year, in time for installation ahead of Discovery being effectively put to sleep at the end of her esteemed career.

“Schedule: RSME delivery will support RSME installation prior to final Orbiter Electrical Power Down. 1st three RSMEs support OV103 orbiter retirement schedule NLT 04/15/2011. Final six RSMEs support remaining orbiter retirement schedule NLT 06/30/2011.”

Specific to Discovery herself, another PRCB presentation on Thursday (57 pages – also available on L2) noted Discovery’s retirement plan in depth, via what is known as an End State Flow Review (ESFR) – including a section on the recommended RSME plan.

“OV-103 (Discovery) SSMEs: Down Mission processing (STS-133). SSME removals – 2nd week of January 2011. PWR current baseline plan – remove and transport flight SSMEs from OPF-3 (Orbiter Processing Facility) to SSMEPF for post-flight inspections and nominal turnaround flight processing,” the presentation listed.

“End State processing (for Display Site): Preferred option (U/R): install (3) Replica Shuttle Main Engines (RSME) in OPF-3, NLT 4/15/2011 (based on needing vehicle power and hydraulics). Perform nominal SSME close-outs with Engine Mounted Heat Shields and Dome Heat Shields. Flight SSMEs to remain in SSMEPF.

“RSME Status: CR in process for the design, fabrication, and installation of RSMEs. RSMEs comprised of scrap SSME nozzles and newly-designed nozzle adapters; three (3) per Orbiter. Ten (10) ‘scrap’ nozzles have been identified and located; minor cosmetic repairs required. Establishment of requirements and preliminary design of nozzle adapters, stiff arms, and attach point brackets continues.”

The outstanding work mainly relates to being able to realign funding for the cost of the RSMEs – which is minimal – and their ability to safely ferry with the orbiters once they head out to their exhibitions. Other considerations were also listed.

“Nozzle scrap / simulated parts / skills may not be available to support repairs required to meet the structural and display requirements within the proposed schedule,” added MSFC, with alternative options including the orbiters going on display without any engines at all.

“RSME Impact – Potential delay in RSME delivery to KSC. Mitigation – PWR proceeding to do early identification of parts needed to support nozzle repair. Mitigation – PWR working within CA operations to identify labor needed to support nozzle repair.”

“RSME delivery later than 04/15/2011 impacts overall OV-103 end state flow and RSME installation for the Orbiter to maintain power capability,” KSC added. “Mitigation – KSC working to identify alternatives for installing RSMEs without full vehicle power capability.”

In recommending the go ahead to build nine RSMEs, the presentation closed with the central reason for the request, again listing the SSMEs as hardware that will gain future use by NASA.

A final configuration of the new HLV is yet to be confirmed, as bodies such as the HEFT (Human Exploration Framework Team) continue to work through their evaluations.

However, it remains “highly likely, if not a certainty” – according to sources – that the new vehicle will sport SSMEs, following on from their initial ‘pre-decisional’ studies which favored an inline SD HLV, with SSMEs on the first stage – starting with the current RS-25Ds, before moving to a cheaper expendable RS-25E version.

“Recommendation & Summary: Recommend authorization and Transition funding to design, build, deliver and install nine (9) Replica Shuttle Main Engines (RSMEs) to replace Space Shuttle. Main Engines (SSMEs) on orbiters. Continue to address RSME integrated threats,” the presentation noted in conclusion.

“Preserves the SSME flight engines for future Agency use.”

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