Thursday, March 19, 2015

Let's light this candle! Part 2

I need one of these. For reasons.
Welcome to 'Part 2' of my experience at the incredible NASA Social for the QM-1 Solid Rocket Booster (SRB) test. If you've not yet read 'Part 1', I would like to invite you to do so before reading this entry. As before, I'd like to thank NASA, the NASA Social team, and Orbital ATK (OATK) for organizing this event, and extending the invitation to so many of us space enthusiasts to witness such an incredible experience as we lay the groundwork for humanity's steps to become a multi-planet species.

As a reminder, security guidelines prohibited recording/photographing anything once inside the security perimeter, so there is a lack of pictures from many of the interesting places we visited...and because I didn't think ahead, neither pen nor paper was in my repertoire...so I'm digging through the recesses of my less-than-perfect memory for much of the information from 'Day 1'. If I happen to miss a detail or two, feel free to mercilessly mock me...or politely correct me - I'm simply pleased you're reading this.

After passing through the gate, we only had a short journey to our first stop. We had to break into two smaller groups to make the tour through the areas more manageable. At our first stop, an OATK engineer gave a brief, but informative, description of one of the omniaxial gimbal bearings being developed for a future SRB (though the one on SLS is very similar). The bearing consists of multiple, alternating layers of a rubber compound and aluminum (I think), which allows hydraulic actuators to move (gimbal) the SRB's nozzle +/- 8 degrees to maintain a proper thrust angle. If your eyes glazed over after reading that, the short of it is this allows the rocket to steer a bit to make sure it's heading in the correct direction.


"Ares I-X launch 08" by NASA
Sandra Joseph and Kevin O'Connell
The group was then ushered into the area where the liner/insulation is applied to the interior of the casing and nozzle. The insulation was the primary culprit in delaying qualification of the new five-segment booster. Though the new SRB was essentially the same as the Space Shuttle's four-segment booster, and practically identical to the five-segment booster used in the Ares I-X test flight several years earlier, NASA was no longer given special allowance to use an asbestos-based insulation as they had been for Shuttle. This meant that booster engineers needed to find a solution that didn't add undue weight while still maintaining the thermal protection characteristics as the now-banned insulation. Unfortunately, there was a reaction between early iterations of the insulation, and the fuel in its liquid-ish state, which created voids/pockets as it cured. These voids were a serious issue and could have promoted a casing/joint burn-through, greatly increasing the likelihood of loss-of-vehicle. It is believed that the insulation problem has been resolved, which has allowed NASA and OATK to proceed with qualification testing.


Our group in front of one of the mixers.
Credit: Orbital ATK
We were also allowed the opportunity to enter one of the propellant mixing facilities. In these hardened buildings, the ingredients are placed into a temperature-regulated 600 gallon "bucket" and mixed until proper consistency is reached. Truly, the machine looks like a super-industrial version of a restaurant floor mixer...albeit with a much more dangerous batch of "cookie dough" to blend. The mixer blades are quite large, and tolerances are tight - while blades scraping on the inside of a metal mixing bowl might be OK when making cookies, stray sparks and unnecessary heat and friction are things to be avoided when blending solid propellant. Due to the high degree of safety required when mixing the propellant, the building is unoccupied during operations and everything is controlled from a remote location. The remote operations center keeps a watchful eye on everything via cameras and sensors. This level of precaution is not unwarranted - in June of 1985, one of these hardened buildings was destroyed while mixing propellant, resulting in the loss of the $3 million facility.

Unlike liquid-fueled engines which have their fuel pumped to them when needed, SRBs need to have the fuel 'cast' into a casing. This casting occurs in a VERY large building, with deep pits designed to hold the huge motor segments while the putty-like fuel is poured/dropped/fed into casings. Since SRBs cannot be actively throttled, varying levels of thrust can be passively achieved by casting the fuel in a particular shape. Since the fuel burns from the inside of the casing outward, the fuel's surface area will change over the duration of the burn...and a change in surface area will directly impact the amount of thrust being generated. This casting is achieved by placing a mold into the segment casing while the fuel is being poured, which creates the desired shape. The three middle segments use the same mold, but the forward and aft segments require molds specifically designed for them.


Other than the actual booster test, I sorely
wanted a picture of the X-Ray facility.
One of the more interesting things, other than the huge X-Ray building we could not enter, was the tour of the SRB stress test area. In this facility, we were shown the results of what happened to the forward and aft sections of the SRB as they were stressed beyond their operational limits. At first glance, the damage didn't look too bad...but closer inspection clearly showed what would've been catastrophic failure in an actual flight. However, this damage only resulted from applying significantly more force to the attachment point than would be experienced during a real launch. It's important to test items not only to their design specification, but to see how far beyond that they can go before failure. In so doing, NASA is helping to design and build the safest human-rated heavy launcher yet.

We ended our day by taking part in a NASA-televised conference featuring many of the key people involved in developing not only the new boosters, but the SLS program as a whole. I've seen Todd May (NASA SLS Program Manager) speak at a couple different events, and I quite like him. It's obvious he's very intelligent, but has an easy manner to his speech that renders him immediately likeable. I've also had the pleasure of hearing Bill Gerstenmaier (NASA Associate Administrator Human Exploration and Operations) speak once before. Though there was not a lot of new information gleaned from the assembled team, it was still an excellent experience and helped set the stage for the next day's static firing.

And on that note, I'll end 'Part 2'. If you're interested in watching a short video about much of what our group saw, please take a look at the NASA Marshall-produced video below. Thank you again for reading, and I hope to have 'Part 3' up soon.