SLS positioning for ARRM and Europa missions

by Chris Bergin

Space Launch System (SLS) managers are conducting a feasibility study into the use of a 5.4 meter payload fairing, with a view to enabling the use of the HLV for the Asteroid Redirect Robotic Mission (ARRM) spacecraft – set to launch in 2019 – and even a robotic mission to Europa. The effort is part of a multifaceted drive to find missions for the Heavy Lift Launch Vehicle (HLV).

SLS Missions:

NASA’s new flagship launch vehicle is currently progressing towards its Critical Design Review (CDR) milestone.

Its development path has so far managed to avoid the serious schedule and design issues suffered during the Constellation Program (CxP).

However, SLS has yet to win over some of its critics who point to the lack of missions for the HLV.

SLS will debut in late 2017 on Exploration Mission -1 (EM-1), a test flight that tasks the HLV to loft the Orion spacecraft on a mission that will send the spacecraft 70,000 km past the Moon on a 25 day flight.

Four years will pass before SLS launches again on Exploration Mission -2 (EM-2), this time with a crewed Orion, sent to rendezvous with a captured asteroid near the Moon.

Z8No specific missions have been allocated to the HLV past EM-2 at this time, as NASA managers work through Design Reference Mission (DRM) options, ahead of negotiations with international partners – who will have to join forces with NASA in order to share the strain of the huge costs associated with deep space exploration.

This “capability” approach builds on available hardware, projected funding and international involvement as the foundation for creating missions for the HLV in the 2020s, during which the vehicle will have to launch a minimum of once per year.

Z53While that roadmap continues to be evaluated, SLS managers have always cited the HLV’s multi-mission capability, envisioning numerous missions to fill in the gaps in an exploration manifest that only requires SLS to launch a handful of times during the next decade.

Without naming specific payloads, NASA managers have previously intimated they expect SLS’ superior upmass capability will attract willing payloads from areas ranging from the Department of Defense (DOD), international partners to the science community.

In an effort to advertise and further evaluate SLS’ versatility, documentation (acquired by L2) portrayed one of the payload fairing options that could be installed on to the HLV, specific to robotic spacecraft.

Z7Titled as “Objective: Determine the Technical Feasibility of Utilizing a RUAG 5.4m PLF on SLS Vehicles & Define a Potential Partnership Approach to Develop the System,” the overview is based on using an Ariane 5 style fairing atop of the SLS.

The Swiss-based RUAG Space has been responsible for the development and production of all Ariane launcher payload fairings.

Currently, fairings are produced for the European Ariane 5 and for the United Launch Alliance Atlas V-500 launch vehicles as well as for the new small European Launcher Vega.

Z9The company note their fairings are built with composite technology based on aluminum honeycomb cores with carbon fiber reinforced plastic face sheets. This construction method allows the combination of low mass with high stiffness.

The SLS team are employing a “Two Way Feasibility Study of the Applicability of a RUAG 5.4m PLF to SLS, via “RUAG assessment using NASA Evaluation Criteria (GR&A), and a “NASA assessment using RUAG PLF definition and NASA Generated Data.”

The intent, as noted by the presentation, is to reconcile the differences between the assessments by the end of study process.

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SLS engineers began working on the study in the middle of 2013 via Technical Interchange Meetings (TIMs), prior to creating the March, 2014 overview. Its current status is at the management review level ahead of a partnership decision.

Z22In providing examples of the fairings usage, two DRMs were provided. The first relates to using SLS for launching the ARRM spacecraft that will head out and capture an asteroid.

Although NASA is still evaluating the type of spacecraft that will conduct this role, scheduled for at least two years ahead of EM-2, current baselines point to an EELV-class rocket as providing the spacecraft’s launch.

Switching that role to the SLS would be a hard sell, not least based on cost, unless NASA creates a path to promote the benefits of providing SLS with a 2019 cargo mission – something that has been previously suggested – as a potential avenue to hand the SLS workforce a mission in-between the large EM-1 to EM-2 gap, whilst also providing SLS with a second test launch ahead of launching with humans.

Z23The second DRM provided – a mission with a spacecraft bound for Jovian moon Europa – would be an even larger challenge to enable, mainly from a funding standpoint.

SLS managers have already made attempts to attract science missions to their manifest, with previous L2 notes showing they have been working alongside the Jet Propulsion Laboratory (JPL) on a notional science mission to the Europa. However, this was an exercise, as opposed to the opening plans for an action mission.

With this new presentation once again citing a mission to Europa in its DRM examples, the SLS team continue to promote the HLV for flagship science missions. However, other – far cheaper – launch vehicle options already exist.

Z27The main problem for enabling such a mission is the funding – or lack thereof – for a robotic mission to Europa, with NASA’s budget strained to the point such a mission only exists at the “pre-formulation” stage.

At present, this mission would likely favor the Atlas V, which is certified to launch spacecraft that require Radioisotope Thermoelectric Generators (RTGs) – developed for deep space missions – to provide long duration power support to the payload.

SLS would require certification for such a payload, which would likely come only after a salvo of missions have proved the HLV’s reliability.

Such an effort – should a Europa mission target early into SLS’ lifetime – would add cost to the mission, which could result in the payload customer/responsible Agency department having to pick up the tab.

Z99SLS also lacks payload access at the pad, which is normally a safety requirement for the installation of RTGs.

The benefit of such a mission being lofted via the superior performance of SLS would result in the mission transit time vastly reduced, when compared to the eight or so years it would take via a current launch vehicle. However, that is not yet a viable consideration when such a mission is a long way from becoming a reality.

The payload fairing study also notes the ongoing work towards an expedited switch to a more capable upper stage known as the Exploration Upper Stage (EUS)formerly known as the Dual-Use Upper Stage (DUUS – pronounced “Duce”) before the name was dropped due to it sounding like a profanity in Japanese.

An article updating the status of that work via L2 documentation will be published in the coming days.

(Images: Via L2 content from L2′s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Other images via NASA)

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