NASA’s Space Launch System (SLS) is continuing to make relatively good progress during its development path, according to the Agency’s key Aerospace Safety Advisory Panel (ASAP). The latest status update on the top issues – ranging from crew safety items of interest to overall schedule – overviewed the main challenges known as “Red Risks”. The ASAP note these risks appear to be “going down, although they have not yet been eliminated”.
The development path for the Space Launch System (SLS) is continuing to avoid the massive issues suffered by its predecessor program, Constellation (CxP).
Had Constellation remained on schedule, the program would have been coming up on the Orion 10 mission atop of the Ares I rocket, its seventh crewed mission to the ISS and four years away from returning humans to the surface Moon via the combination of Ares I, Orion, Ares V and the Altair lunar lander.
Of course, the Vision For Space Exploration (VSE) “Moon, Mars and Beyond” related manifest – produced in 2006 (available in L2) – was soon to suffer from major schedule slips via technical and funding challenges, ahead of the program’s eventual demise at the end of the decade.
The new program, finally confirmed after a number of lengthy technical and costing studies, removed the Moon from the exploration plans – at least from a surface crewed landing standpoint – with a more specific focus on the eventual goal of sending humans to Mars.
That end goal is still without any real specifics, with only vague references of “sometime in the mid-2030s”, partly due to the political funding uncertainty surrounding missions that won’t be close to becoming a reality under the current or the future President.
This hasn’t stopped NASA’s PR drive using the #journeytomars hashtag on nearly every piece of information that has any relation to SLS, while the rocket itself continues to be incorrectly portrayed in official renderings as “painted white”, so as – according to some SLS team members – “to avoid it looking too much like the cancelled Ares V“.
In reality, the media folk shouldn’t be too concerned about any aesthetic association between SLS and its cancelled predecessor, given Ares V was still tucked away out of sight and out of mind on the drawing board during the period Constellation workers battled to find solutions to Ares I’s technical and schedule woes.
Meanwhile, SLS has progressed past the point the Constellation Program was cancelled, as the rocket enjoys much calmer waters during its path into the Critical Design Review (CDR) milestone.
Although the rocket still has the major issue of finding interested payloads, other than Orion, to utilize its superior capability – in turn creating enough missions that will provide it with a viable launch rate – its development path to becoming operational has yet to suffer from a major red flag.
In summarizing what was described as an extremely comprehensive overview by Bill Hill, Associate Administrator for NASA’s Exploration Systems Development (EDS), the ASAP was provided with updated information on the three main arms of NASA’s deep space system – namely SLS, Orion and the associated ground systems (GSDO).
How those three programs interact with each other has been an item of interest to the ASAP, to which they were informed a Cross-program System Integration (CSI) team handles the interactions between the three bodies.
“They range from relatively simple interface control document (ICD) agreements to more complex items in terms of risk assessments and opportunities to improve performance,” noted the ASAP minutes. “Products are on schedule and the cross-program interdependences (those elevated to ‘watch’ level) have dropped dramatically.
“This means that the programs are getting better at talking with each other and working out the interactions at a lower level to preclude elevation for resolution at the leadership level.”
The ASAP members were told the interfaces are becoming stable and well-defined, which is “very good news”.
The panel was also told that items of interest from the last overview are all being mitigated, while the only new issues were relatively minor, per their primary interest and responsibility, i.e. crew safety.
“There is a concern with gaseous hydrogen buildup just prior to RS-25 start and how that will be handled,” added the minutes as an example. “If there is a problem, there is the potential of using a burn-off. That research is ongoing.”
That reference may relate to ongoing work by SLS engineers on the improvements to the all-important hydrogen burn-off system, or Radial Outward Firing Initiators (ROFIs), as recently overviewed in an article in June.
Another reference to the ASAP refers back to the early days of the Constellation Program, specific to recovering the crew from Orion post-splashdown.
Early concerns focused on the recovery of the crew from the sea during an off-nominal landing – as referenced in 2008. The details were refined once again in 2012, including the unthinkable scenario of a crew having to survive on their own for 24 hours until rescue.
However, the ASAP heard of evaluations relating to high sea states and the recovery of the crew within just a few hours, a delayed process due to high sea states in the splashdown zone.
“There is the question regarding the goal of crew recovery within two hours of splashdown. Under certain sea states, that is a difficult task,” added the minutes, classing it as a new concern. However, the ASAP appears to be satisfied this won’t become a crew safety issue.
“It may mean getting the crew out within two hours and allowing recovery of the capsule to take longer under certain sea states. This seems to be a reasonable safety mitigation.”
The ASAP also heard about ongoing work relating to Orion’s heat shield that may result in a design change from monolithic heat shield to a block heatshield – although no decision has yet been made at the Agency level.
There is also ongoing interest into the larger-than-expected amount of MMOD damage suffered by the EFT-1 Orion during its test mission last year.
Another issue concerned “pendulum risk” – relating to an event where one of the three Orion parachutes fails, resulting in a pendulum effect where there is oscillation of the suspended Orion spacecraft under the parachutes.
The Orion program is continuing to test the parachute system – including failure scenarios – with the next drop test scheduled to take place on August 26.
However, the ASAP members were told that the biggest concern is the launch date for SLS’ maiden flight, Exploration Mission (EM-1), which is currently expected to take place in the middle of 2018.
The launch target remains on track, but the ASAP want to ensure that technical problems do not arise via a scenario where tradeoffs may be inserted to protect that schedule.
“Probably the largest risk area is in risk to the currently configured EM-1 launch date,” added the minutes. “Schedule is a continuing issue as budgets drive schedule and technical problems arise. That is a programmatic risk and is a concern, and it is being closely monitored by the Program.
“Currently, it is not a direct safety risk unless someone starts to make safety tradeoffs in order to gain schedule. That is something that the ASAP looks for continuously.”
However, the ASAP’s overall view on the status on the SLS program appears to be mainly positive, per the Technical Program Metrics (TPM) summary report – which noted the ‘red’ risks “appear to be going down, although they have not yet been eliminated.”
(Images: Via NASA and L2 content from L2’s SLS specific section. SLS renders by L2 artist Nathan Koga)
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