ASAP Report Targets Concerns Over SpaceX Propellant Loading

Credit: USLaunchReport.com
Credit: USLaunchReport.com

A new NASA reports says that while Boeing and SpaceX are making progress on their commercial crew spacecraft, but a number of key technical challenges remain and there is “a very real possibility” of “a substantial slip in the schedule” in the already delayed programs.

In its 2016 Annual Report, NASA Aerospace Safety Advisory Panel (ASAP) said it was concerned about SpaceX’s “load and go” approach of placing the load aboard the Crew Dragon spacecraft prior to loading the Falcon 9 booster with propellants, particularly in the wake of the loss of a booster in September while it was being fueled.

“A number of systems have not yet finalized design or completed testing. Challenges remain in several key systems, such as abort and parachute-related systems, in anchoring the analysis required to certify those systems for human flight,” the report states. “Additionally, there are issues and concerns surrounding the launch systems of both providers, such as the Centaur fault tolerance for Boeing and the ‘load and go’ approach for SpaceX.”

Boeing will be flying its Starliner spacecraft on a modified United Launch Alliance Atlas V, which uses the Centaur upper stage. The Centaur is being upgraded with dual engine capability from the single-engine configuration that ULA uses to launch satellites.

SpaceX’s “load and go” approach is a reversal of procedures that have been used in human spaceflight since the first missions in 1961. The standard practice is to load the launch vehicle first with no personnel at the launch pad, let the rocket settle and its fuel settle, and then place the crew on board with a minimum number of support staff.

SpaceX is using densified (super cold) liquid oxygen (LOX) in the Falcon 9 booster that will launch the Crew Dragon spacecraft. The densified LOX gives the rocket extra payload capacity, but it must be loaded just prior to launch to keep it from warming up. As a result, the company wants to load the crew first.

SpaceX began flying with densified propellant in late 2015 as part of an effort to recover the Falcon 9 first stage for later reuse.  The densified propellant helped offset the performance hit from adding landing legs and other systems to the booster.

NASA’s International Space Station Advisory Committee raised concerns over load and go in 2015. Those concerns were heightened on Sept. 1 when a Falcon 9 caught fire and exploded while it was being fueled on the launch pad for a pre-flight first-stage engine test. The accident destroyed the booster and a $195 million communications satellite.

“One complicating factor for the ‘load and go’ issue is the potential uncertainty in hazard identification and control,”the ASAP report states. “Identification of the hazards is dependent on many factors, which include understanding the environment in which the system will operate.

“In this regard, the Panel is concerned that the dynamic thermal effects on the system associated with loading densified propellants may not be adequately understood, which results in a higher level of uncertainty that must be factored into the risk determination,” the report adds.

SpaceX has said its investigation pointed to a breach of a helium tank located inside of the second stage liquid oxygen (LOX) tank. Investigators concluded that oxygen pooled and froze inside buckle (gap) between the helium tank’s aluminum tank and a layer of carbon composite material that surrounded it. This caused friction or the fibers to break, igniting the composite material.

SpaceX plans to return to flight on Saturday using warmer helium, which it believes will prevent a recurrence of the explosion. The company also plans to change how it manufactures its helium tanks to eliminate buckles between the aluminum and carbon composite shell.

Whether those changes will be enough to satisfy NASA is unclear. Losing a communications satellite or space station resupply ship is one thing; crew safety standards are a lot stricter.

The ASAP report was completed before the investigation into the accident was completed, so it does not comment on SpaceX’s proposed fixes. The panel did have advice for NASA about how to evaluate the risks involved in the load and go approach with regards to Crew Dragon flights.  (Emphasis mine)

We believe that the focus of the investigation must not be solely to identify and fix the specific cause of this mishap. It must focus also on improving the understanding of how the system functions in the dynamic thermal environment associated with “load and go” so that other previously unidentified hazards can be discovered.

This is not a trivial effort. Despite testing at the component and subassembly level, systems often display “emergent” behavior once they are used in the actual operational environment. We are concerned that any determination of risk associated with “load and go” would have significant uncertainty.

For these reasons, we strongly encourage NASA top management to scrutinize this issue and ensure that any decision to accept additional risk or novel risk controls with large uncertainties is justified by the value that will be gained. The decision should not be unduly influenced by other secondary factors such as schedule and budget concerns.

In short, the panel is saying that NASA need to make sure the benefits of using densified propellants are really worth the risk. The rewards are basically an increase in payload to the International Space Station.  ASAP is also telling NASA not to let schedule and budget concerns override safety.

As for schedule, ASAP has some serious concerns about that for both SpaceX and Boeing.

“Although progress is being made, there is still much left to do from a technical perspective,” the report states. “Whether the needed work can be accomplished without a substantial slip in the schedule remains to be seen.”

Each company must conduct two demonstration flights to the International Space Station and then have their systems certified to carry astronauts on a commercial basis. The current flight test schedule is:

  • SpaceX Demonstration Mission 1 (No Crew): November 2017
  • Boeing Orbital Flight Test (No Crew): June 2018
  • SpaceX Demonstration Mission 2 (Crew): May 2018
  • Boeing Crew Flight Test (Crew): August 2018

Whether the schedule will hold is uncertain. The ASAP report notes that “the designs of proposed spacecraft systems are not fully mature and are still in a state of flux.”

Boeing is running 16 months behind schedule on the flight test without a crew and 15 months behind on the crew flight compared with the schedule laid out in the  Commercial Crew Transportation Capability (CCtCap) contact it was awarded in 2014. SpaceX is running 20 months and 19 months behind schedule on its two flights.

A report issued by the NASA Office of Inspector General (IG) in September indicated that neither company was likely to fly astronauts to ISS on a commercial basis before the end of 2018. This is key for NASA because its contract to fly U.S. astronauts on Russian Soyuz spacecraft expires at the end of that year.

The NASA IG report attributed the CCtCap delays to technical challenges faced by Boeing and SpaceX and bureaucratic delays at NASA in reviewing documentation submitted by the two companies.

There are two main review processes under way. One involves standards for systems and equipment proposed by the companies that they feel are comparable to requirements laid down by NASA. The other involves hazard reports on how the companies plan to address specific dangers to the vehicles and their crews.

The ASAP report said NASA and the companies have been making progress in dealing within both areas, but it added that the amount of work remaining to be completed could cause additional delays.

“Virtually all requests for alternate standards have been received, and some 95 percent have been adjudicated and approved by NASA,” the report states. “The approval of these standards is basic to allowing the designs to proceed to completion. In addition to alternate standards, between 65 and 75 percent of all requested variances and Phase II Hazard Reports (HRs) have been reviewed by NASA and dispositioned.”

Another area of concern for ASAP are the calculations for loss of crew (LOC), which appears unlikely to meet NASA’s original goal.

“The ASAP was informed that the LOC goal of 1 in 270 may not be able to be met without additional spacecraft mitigations due to Micrometeoroid and Orbital Debris (MMOD)-associated risks, which are a dominant factor in the LOC calculation,” the report states. “Since the designs of proposed spacecraft systems are not fully mature and are still in a state of flux, it is impossible to determine what the final configurations will yield with respect to LOC.”

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

  • Vladislaw

    “and bureaucratic delays at NASA in reviewing documentation submitted by the two companies.”

    Did the report what kind of delays these were? Funding? Lack of personal? Congressional tinkering?

  • Carlton Stephenson

    I read somewhere that it had to do with the turn-around on requests for alternate standards. Both contractors want to use things and processes not done 50 years ago which leaves no ‘mature’ anything for reviewers to recognize and feel at ease.

    You have to wonder, though, how Dreamchaser would have looked in this context had the Commercial Crew award gone three ways. It’s a long way out, but if the primary two keeps slipping… And isn’t that exactly how they got in on COTS-2 (Vehicle failures of both Orbital and SpaceX)?

    Bet NASA is wondering the same thing.

  • Mr Snarky Answer

    Probably not. The effort to fly an un-faired lifting body is way more difficult than aerodynamic modeling a capsule, and Boeing managed to screw that up the first time around. DC also planned originally to use hybrid engines similar to those they developed for VG….how did that work out? All doable, and have a soft spot for DC, but don’t think there is any easy button over there.

  • Paul_Scutts

    NASA concerns re. “load & go” will hopefully end up being a Y2K type issue. By the time a crewed Dragon lifts off, SpaceX will have had, in all likelihood, scores of successful launches with the new He bottles/loading procedures.

  • Richard Malcolm

    Indeed – if Dragon and Starliner have had such hiccups, one can only imagine how far behind the ball Dreamchaser (a vehicle I also have a soft spot for) would be by now.

    What SpaceX and Boeing are attempting now is extraordinarily difficult, something only attempted to date by the greatest spacefaring powers; and NASA and Congress haven’t helped.

  • Lee

    Minor nit:
    “scores” is defined as multiples of 20. One “score” = 20. If SpaceX flies crew by the end of 2018, it is pretty doubtful they will have “scores” (which I would argue is at least 60, but I’m doubtful they’ll even have 40 more launches by then, which is the minimum definition of “scores”) of launches between now and then.

  • Vladislaw

    True but SpaceX and Boeing are NOT trying replicate 50 year old capsule tech or what the Russians are flying. They are both trying to incorporate cutting edge into the designs, both materials and electronic/computing.

    There is good talk by David Gump, ex CEO of Deep Space Industries talking about innovation by gov.

    https://www.youtube.com/watch?v=OoNjSADM9H4

  • getitdoneinspace

    We are at an interesting point in history. I am an older gentleman and often think of the significant advancements made by my father’s generation. I know during my generation (the take no risk generation) significant advancements like landing on the moon and building the interstate highway system likely would never have occurred. I am hoping society is at an inflection point in terms of risk tolerance and my children’s generation will be able to do great things again. A society intolerant of risk will slowly deteriorate. A society tolerant of measured risk has limitless potential. This specific decision making process will shed some light on if we are at this inflection point or if we will continue on the slow path we have been on since the 70’s.

  • Richard Malcolm

    True but SpaceX and Boeing are NOT trying replicate 50 year old capsule tech or what the Russians are flying. They are both trying to incorporate cutting edge into the designs, both materials and electronic/computing.

    An excellent point -and helps underline just how great is the challenge they’re undertaking.

    These two crew capsules will be the most advanced and, in many respects, most capable ever operated.

  • Paul_Scutts

    You’ve made a very valid point, Lee, thanks for the correction. Regards, Paul.

  • windbourne

    thank you.

  • Bernardo_de_la_Paz

    Yet which are both rather archaic and underwhelming compare to the 1970’s vintage technology shuttles. Not that the shuttle came anywhere close to its expected cost savings, but before they are even operating, Dragon and CST-100 are already even more expensive to operate on a cost per capability basis. We’re stuck with them now, but in hindsight we would have saved money if we had just kept flying shuttle instead. Note that I am not claiming that says good things about shuttle.

  • Richard Malcolm

    I don’t know what you mean by “archaic and underwhelming.” Is it because they’re capsules rather than gliders? Or is it because the Shuttle had a large indigenous cargo capability that the Commercial Crew vehicles do not? Because in either case, it’s become apparent that capsule architecture is more advantageous – and safer – than a glider or lifting body (especially so with Dragon, which has a pinpoint landing capability via its Super Draco thrusters, which will be used on later CRS flights) – and that at present it makes more sense to deliver crew and cargo separately to orbit. A Shuttle is kind of overkill for just delivering 2-3 astronauts and a few thousand pounds of supplies, isn’t it?

    In fact, it’s not at all clear that STS was more cost effective than the Commercial Crew vehicles. A Shuttle flight cost about $450 million at the end of program in 2011 (exclusive of cargo costs). SpaceX (to take one example) gets $133 million for each CRS flight in a capsule which has the same crew capability (7) as Shuttle – though it will rarely need to use it. But even at that, this does not factor in the cost of the Launch On Need (LON) Shuttles that were required to be ready on standby post-Columbia disaster, nor the ongoing cost of maintaining the large ground support staff of the Shuttle program.

    In any event, none of this even takes into account the safety concerns. Unlike Starliner and Dragon, the STS orbiter had no LES of any kind, leaving the crew without any effective escape option during most of its launch profile. Nor was there any truly effective resolution for the problem of foam strikes on the TPS of the ventral side of the orbiters. And safety concerns were, after all, a key reason why STS was retired.

    I think there’s an argument to be made about having tried a limited extension of STS on a reduced schedule basis to narrow the gap in flight between the end of its service and the arrival of Commercial Crew, so as to at least reduce dependence on Soyuz for crew transportation – assuming that decision had been made early enough to preserve the necessary production lines and tooling. But that’s a different discussion than actually keeping Shuttle over Commercial Crew. And even such an extension would have incurred heavy costs that would have to have come from another budget ledger – probably SLS and Orion.