SLS launch rate requires repetitive cadence – Gerstenmaier

by Chris Bergin

NASA’s Space Launch System (SLS) will launch at least once per year, as a “necessary” requirement, according to Bill Gerstenmaier. NASA’s Associate Administrator for Human Exploration and Operations recently addressed concerns over the near term schedule for the monster rocket, which will not launch humans until the next decade.


The new Heavy Lift Launch Vehicle (HLV) is enjoying a surprisingly smooth ride through its development cycle, ultimately remaining on track for a 2017 debut.

Z9A delay of six months to the first mission – known as Exploration Mission -1 (EM-1) – was feared ahead of the latest milestone review, known as Key Decision Point C (KDP-C), related to problems with the European contribution to the Orion Service Module.

However, the milestone was passed, with the launch date unaffected.

EM-1 will involve SLS debuting with the second Orion to venture into space, conducting an uncrewed mission 70,000 km past the Moon on a 25 day flight.

This mission was changed from an Apollo 8 style mission around the Moon, in order to gain experience ahead of the Exploration Mission -2 (EM-2) mission.

Z89EM-2, launching in the 2021 time frame, will be the first crewed mission for Orion, tasked with rendezvousing with a captured asteroid in order to conduct EVAs and return samples back to Earth.

This initial leg of the exploration roadmap is aimed at fulfilling President Obama’s goal of an asteroid mission before the middle of the next decade.

This plan has received criticism, ranging from a lack of public inspiration to concerns over the large gap in flight operations between EM-1 in 2017 and EM-2 – the latter of which has no guarantee of launching in 2021.

Recently published minutes from the latest NASA Advisory Council (NAC) Human Exploration and Operations Committee (HEOC) once again portrayed negativity towards the plan.

Mr. Ken Bowersox – HEOC chair and Mr. Bohdan Bejmuk – co chair – both grilled Mr. Gerstenmaier at the meeting, citing concerns about the lengthy path towards crewed flights on Orion.

Questions included why the first flight – EM-1 – was uncrewed, through to the overall flight rate of the multi-billion dollar SLS.

Z3Following Mr. Gerstenmaier confirmation that the pacing item for the first crewed mission was the development of the Environmental Control and Life Support System (ECLSS) and related budget constraints for Orion, Mr. Bowersox claimed it “will not excite people” to launch an uncrewed EM-1 mission in order to save funds in the short term human rating drive.

Notably, the 2017 launch date for SLS is heavily associated with the 2010 Authorization Act, which requested SLS and Orion to be ready to launch in that time frame as a back up to the Commercial Crew Program (CCP).

This back up plan was to be implemented in the event the CCP suffered a major issue, an issue that negated the future possibility of removing the burden of having to pay top dollar on Soyuz seats, a current post-Shuttle requirement to allow US astronauts to continue a permanent presence on the International Space Station (ISS).

This plan has been blighted with irony, given the CCP has been delayed by over two years, largely due to shortfalls in funding, arguably in protection of SLS and Orion budget lines, in turn resulting in hundreds of millions of additional NASA dollars being sent to Russia for extra Soyuz seats, all while SLS and Orion have never been in a position to launch a crew on the 2017 flight.

Z6Design Reference Mission (DRM) documentation showed the SLS Block 1 launching an Orion to the ISS.

However, because the HLV was designed for Beyond Earth Orbit (BEO) missions, it would be so overpowered, its payload would have include a large amount of ballast.

This DRM is called “LEO_Util_1A_C11A1 – ISS Back Up Crew Delivery Per Congressional Mandate – NASA is to provide backup capability to the commercial ISS crew delivery and return option,” per the latest Exploration Systems Development (ESD) Concept of Operations (ConOps) document, available in L2.

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Although the ISS back up mission has effectively been removed from the overall plan, the fallout on the schedule has effectively tasked SLS with launching much ahead of its optimum launch date.

A potential SLS cargo mission in 2019 has been mentioned a number of times in internal conversations.

However, that is classed as doubtful, based on documentation that points to the availability of the specific Interim Cryogenic Propulsion Stage (ICPS) units, with only two on order – one for EM-1 and another for EM-2, both in the time frames of the two missions.

Once SLS has completed its political role with EM-1 and EM-2, a mix of cargo and crewed missions are expected, launching at least once a year. SLS is currently projected to have the capability of launching once every six months.

Although payloads are yet to be announced, Mr. Gerstenmaier confirmed the flight rate has to be once a year as a minimum requirement, in response to a question from Bejmuk – who had assumed SLS would only launch once every two or three years.

Z53Mr. Gerstenmaier noted that “repetitive cadence is necessary” as the reason SLS will launch every year.

Although no payloads past the EM-2 flight have been revealed, managers have been quick to both promote SLS’ unique capability to potential military and commercial customers, and to the science community.

A cargo version of the Block 1A/B SLS – with its 105mT capability – is often mentioned as the workhorse that will be available for hire throughout the 2020s.

International cooperation is also a major factor, with Mr. Gerstenmaier adding Design Reference Missions (DRMs) remain under evaluation, with a focus on discussing potential missions with international partners. The NASA AA added the Agency will discuss the roadmap with partners when they meet in Japan in 2015.

Given NASA’s budget simply does not allow for it to go on a payload spending spree, international interest in utilizing SLS is likely to be key to the health of its manifest in the 2020s.

(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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