SLS planning focuses on dual phase approach opening with SD HLV

by Chris Bergin

Uncertainty over the configuration of the Space Launch System (SLS) Heavy Lift Launch Vehicle (HLV) may soon come to a close – at least for the interim – with a plan solidifying for using a 70mt Shuttle Derived (SD) HLV to perform a handful of flights, while another “open competition” for the main “Phase 2” HLV decides on the configuration of the launch vehicle for the Beyond Earth Orbit (BEO) missions in the next decade.

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While commercial cargo and crew supply lines to the International Space Station (ISS) continue to press towards being up and running by the middle of this decade, NASA’s next flagship launch vehicle has been bogged down by studies and political brinkmanship, mostly from within the Agency itself.

At an engineering level, the RAC (Requirements Analysis Cycle) studies are coming to a close, with three teams working on potential LV architecture which has a focus on a sustainable path towards the sending humans beyond Low Earth Orbit (LEO) to destination which continue to sway between the Moon and Near Earth Objects (NEOs), with the eventual main goal of manned missions to Mars.

As a baseline instruction to the Agency, the NASA Authorization Act demands the SLS should be up and running by 2016, with a report on how this could be achieved due back in January of this year.

Instead, NASA bosses sent lawmakers a preliminary report, heavily angled to claim 2016 was not possible, both on schedule and cost, whilst adding caveats that the findings on a number of get-wells on the cost of the SLS – including the discovery of “greater efficiencies” and even a potential change of design to the SD HLV – were still being evaluated.

Since the preliminary report, mixed messages have continued, not least at the Administration level, although the basis of a plan is now being widely touted at several of the key NASA centers.

This plan (L2), subject to tweaking, involves the leading RAC-1 vehicle, a 70mt SD HLV (Block 0), which it is claimed can be delivered on cost and schedule. The SD HLV Block 0 would become known as the Phase I SLS, flying four missions from 2016, ahead of the Phase II SLS debuting early in the next decade.

The Block 0 SD HLV SLS is driven by three Space Shuttle Main Engines (SSMEs) – utilizing the existing 12 flight engines left over by the Shuttle Program – a stock length ET (External Tank) based core, with two Solid Rocket Boosters (SRBs). The Block 0 vehicle is without an Upper Stage.

The boosters would be four segments boosters, although there are notes claiming the SRBs would be based on the RSRMV-1, which is the Ares I/V five segment booster, with the middle segment removed.

The RSRMV-1 is understood to have better performance than the current four segment Reusable Solid Rocket Motor (RSRM) used by the Shuttle, whilst retaining a number of get-wells, such as avoiding the restart of the Shuttle four segment production, and the ability to use Ares SRB hardware.

The four flights of the Phase I SLS would be classed as test flights, with missions yet to be determined, although Orion – or the MPCV (Multi-Purpose Crew Vehicle – as NASA managers now insist on calling it) – will be flown, allowing for missions of crew and/or cargo to the ISS.

The Phase I SLS would fly from Pad 39A, via a modified Fixed Service Structure (FSS) and Mobile Launch Platform (MLP).

The configuration of the Phase II SLS would placed on backburner until the 2013-2016 timeframe, when an “open competition” would be held between several configurations, such as a 130mt SD HLV from RAC-1, the RP-1 vehicle which has been leading the RAC-2 studies, or even a super-heavy EELV or SpaceX Super Heavy.

The Phase II SLS would launch from Pad 39B, which is currently being demolished to make way for a “clean pad”.

No actual “leading candidates” for the Phase II SLS have been listed on documentation, or cited by sources, at this time – although it is likely to be a battle between an evolved SD HLV and the RP-1 powered options, due to their favor at the RAC studies.

This vehicle’s role is focused only on BEO missions, in other words to a NEO (asteroid) or what is now becoming more likely – a return to the moon. While the lunar destination was wiped out via the death of the Constellation Program (CxP), a reignited political will is not going unnoticed within the SLS planning groups.

As far as further changes to the plan of a dual phased approach to the SLS, time is running out, with documentation and sources citing the much-awaited final report is expected in June, some schedules showing a specific date of June 20.

It is highly expected the Block 0 SD HLV will be represented as the winning option for the interim requirements of the NASA Authorization Act.

Meetings to emphasize the direction are expected to be conducted between NASA and lawmakers from early May.

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SLS Decision Required:

The need for definitive decisions to be taken, and taken soon, can also be seen in a mid-April Program Requirements Control Board (PRCB) presentation by the Shuttle Propulsion Assets Assessment Team (SPAAT), who note the “scope and level of intensity/urgency is highly dependent on the SLS Architecture Selection.”

SPAAT have established an “Integrated” team to fill a void that presently exists between the close out of the Shuttle and Constellation Programs and the start up of the new SLS program, ensuring assets relating to – for instance – the SSMEs and SRBs remain in place, per the current leading forward-plan.

“To provide a plan and a process to ensure that propulsion assets/capabilities from Shuttle and Ares are retained for the new program(s). To develop a team approach that will include all SSP, CxP, SLS, and Center Institutional “Stakeholders”. To provide a clearing house to work issues and provide recommendations to management for the resolution of these issues,” outlined the presentation (L2).

“Issues Include: Contract responsibilities between MSFC, KSC & JSC. Equipment disposition between SSP, CxP and SLS. Work requirements for building assets (MP labs, Engine shop). Work coordination of documentations between all parties. Created a single entry point for all new request for SSP propulsion and CxP assets needed by SLS.”

Preparing for an expected positive decision on a SD HLV configuration is cited as an example in the presentation.

“The team will work with the different organization to ensure that, what ever architecture is selected by SLS, the capabilities and assets specific to that system can be identified for transfer,” the SPAAT added.

“An example as follows: If a shuttle derived system is selected then we will work with projects like SSME, J2X, RSRB, KSC Launch and Landing, Orbiter, & ET. All other systems that would be needed to support SLS propulsion needs such as orbiter feed lines would be coordinated with appropriate Shuttle and CxP elements.”

However, given the current uncertainty into the approved design of the SLS – something which will continue until the final report is approved by all relevant parties – the SPAAT members are utilizing a “Triage Approach” for support and gap Coverage.

“SLS requirements currently not well defined (What transfers vs. disposal). No SLS contracts in-place to transfer the ownership. Seek approval to utilize existing contracts to assure assets and capabilities are maintained until new contracts are in place.

“Examples: Shuttle Assets/Capabilities Matrix in-work, SSME Storage location in work (PWR support to maintain SSME). Shuttle Orbiter MPS Hardware needed for SLS in work. Maintain selected Vendor support. Will utilize SPOC where needed through closeout effort for short periods of time to accomplish work at KSC. Coordination with JSC on this approach. If approved will need to close loop at HQ.”

(The progress on the SLS evaluations will be followed up over the coming weeks. L2 members, follow our exclusive RAC coverage via the HLV tag. Images used:  Via L2 content and photos).

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