A Burning Need... (Part 2)

As the testing of the F1 evolved, it became clear that harmonic instabilities were causing failures. Of course, these instabilities had always been present in rocket engines. They are caused by acoustic pressures building up unevenly and zinging around inside the engine. In the smaller combustion chambers of engines past, they were not so destructive. But inside the massive F1 combustion chambers, these instabilities could become crippling.

Tired of watching their rocket motors exploding, Rocketdyne engineers decided to take control of the process in a unique way. Rather than allowing the acoustic instabilities to initiate and build on their own, they took a "sour grapes" approach, designing an explosive device that could be inserted into the engine upon firing on the test stand. Then, rather than waiting for the instability to build up unpredicted, they could set off their bomb (which was of a known power and yield) and watch a similar acoustic instability build... but with increasingly predictable results.

Eventually, between tests such as the above and many, many redesigns of the injector plate among other components, most of the problems were resolved and the F1 engine was tested in flight and declared flightworthy and man-safe.

However, this is not quite the end of the tale... for as the Apollo program sped on to it's triumphant arrival on the moon in 1969, the Saturn V and the F1 engine continued to have teething pains... the Pogo effect.

A Burning Need... (Part 1)

The development of the Saturn V rocket entailed incredible challenges, but perhaps none so daunting as the creation of the F1 rocket engine, the first-stage powerplant for the mighty booster. Approved for development in the 1950's by the US Army (because, if for no other reason, the Soviets were developing big rockets), the F1 project migrated to NASA when the agency was created. The contract went to Rocketdyne in Canoga Park, California, a division of North American Aviation. This was a huge leap in rocket engine design, and while some of the notions involved were in effect a scaling-up of existing designs, much of the work was well beyond anyone's experience. At this time, large rocket engines were producing on the order of 100,000 or (later) 200,000 pounds of thrust... the F1 would create 1,500,000 pounds! And while cryogenic engines were the trend of the future (supercool mixtures of liquid hydrogen and liquid oxygen), the F1 would produce this power from a mix of liquid oxygen and plain old kerosene.

But early on, the project exhibited growing pains. One major area of concern was combustion instability. When a combustion chamber is scaled up to these dimensions, and the mixed fuels are ignited inside, acoustic waves begin slamming around the chamber and can cause big problems. And in those days, before CAD programs and when computers, such as they were, used that modern innovation- the punch card- engine designs were tested by building and firing. As often as not, they exploded, and the fragments were gathered for a failure analysis. The F1 exploded a lot. And the reason, in most cases, was the gremlin of combustion instability. But the Rocketdyne engineers had a solution in mind, straight out of their collective WWII experience with that simplest of argument solvers, high explosives...

[TO BE CONTINUED]

Beauty in the Infrared

OK, this week's post is a cheat... but only because it is so incredibly cool. Space.com just posted images form NASA's WISE orbiting telescope, launched in 2009 and shut down in February 2011. The reason for the short lifespan? For one thing, the liquid hydrogen coolant that allowed the 'scope to function at infrared wavelengths ran out, and for another, NASA's funding ran out, so an extended mission was not approved. A pity that, for as JPL has so ably proved over the years, an asset in place (i.e., one that has left Earth's gravity well) is always more valuable than another on the drawing board. But what a haul WISE made! Check out these images, all in the infrared and enhanced for human viewing.

Welcome to Mission Control

I've been presenting leadership lectures at Johnson's Apollo Mission Control for a few months now, and every trip there is like a trip to the Church of Apollo. If you ever have a chance to visit, make sure you sign up for the Space Center Houston tour which includes this stop. number of years ago, someone at JSC realized that the old MCC was something special, and should not be repurposed for shuttle control (as the other one was). So with an ultimate partnership with the National Parks Service, the Apollo control room was, so to speak, "mothballed in place" and looks much the same as it did when the last lunar landing flights departed Earth orbit.

Our program gave us the chance to view the fine movie Apollo 13 from the very seats featured in that film. Nothing like sitting at Gene Kranz's console as you watch him (well, Ed Harris) make life-or-death decisions... fantastic.

Of course, there are changes over time. The consoles no longer light up, due to safety considerations. The carpet is very worn, but at this point cannot be replaced due to asbestos abatement expenses. And so many more issues. But the basic structure is there, with the consoles, the chairs, the pneumatic messaging tubes, and all the rest. Just fantastic.

If in Houston, make sure to put this at the top of your list!

Take Care, Endeavor

The current shuttle in orbit, the penultimate flight of the STS program, has tile damage. Seven areas of concern have been indentified by observation from the space station. At this point, they are not considered to be a danger to the return of the orbiter, but more investigation is needed. See details here.

The damaged areas range in size, but a few are larger than a deck of cards. Of course, the depth of the gouges and shape of them will play a role in the decision to fix or not fix. Also, location on the orbiter matters a lot- the temperature buildup in that particular area plays heavily into the equation.

The worst case scenario? A docking with the space station, crew transfer to safe haven, and return to Earth via Atlantis or a Soyuz. Then there would need to be a decision whether or not to attempt an unmanned, computer driven landing with Endeavor. In theory it could be done, and the Soviet Union long ago flew (and landed) their own Buran shuttle unmanned, but for the US shuttles, it is an option previously tested only with a human crew onboard.

As is most common, the damage was from pieces of foam insulation from the external tank (ET). The tank in question was older, having previously survived a hurricane that ripped through the assembly facility, with foam insulation that was over 10 years old.