Thursday, June 23, 2011

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.

Monday, June 6, 2011

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...


Thursday, June 2, 2011

Beauty in the Infrared

OK, this week's post is a cheat... but only because it is so incredibly cool. 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 the Missions to the Moon book blog. This is a place to re-live the heady days of the Apollo and Soyuz lunar programs- perhaps the crowning achievements of the 20th Century. Many blog entries will include a new downloadable image or artifact from the space age- items rarely seen and not available in print. It's all in the spirit of my newest book, Missions to the Moon- to remember the great adventure of the Golden Age of space exploration, and ponder what wonders await us in space.

For more info on the author, go to