Saturday, October 27, 2012

A Fistful of Redstones

Fifty-one years ago today, on October 27th, 1961, the largest flying machine ever built by Wernher von Braun's rocket scientists to date smashed into a million pieces two hundred and fourteen miles southeast of Cape Canaveral. This event marked a veritable victory lap for von Braun's team, and also signaled the end of a technological battle between two branches of the United States military.

Don't you love stories that start out this way? I know I do. Let's back up a bit and go over the details.

Military Missiles

After the end of World War II, the three major branches of the military were crazy for establishing missile superiority - - not with other countries, but between the other branches of the US military. The Army led the development race, building Inter-Regional Ballistic Missiles (IRBMs) such as the Redstone and Corporal rockets under the guidance of von Braun's Peenemuende team. The Air Force, denied the benefits of Operation Paperclip, built their own Goddard-derived rockets in the Atlas and Titan series. The Navy, having no budget for a big missile development program, concentrated on their tiny Vanguard missile program.
Picking the next generation of missiles was a matter of using what worked already.
 The success of von Braun's Jupiter rocket after the failure of the Vanguard rocket as a response to the launch of Sputnik put the Army's Redstone / von Braun team in the prime position to build future heavy-lift launch vehicles. The main restraint was that there was still a branch limitation on long-distance rocketry. The Army could still build interregional rockets, but the Air Force's Ballistic Missile Division was the only organization allowed to negotiate for boosters capable of intercontinental or orbital reach. Even after the Redstone group was assigned to the civilian NASA organization, the Air Force restrictions stood in place.

Wernher von Braun's team knew that the next generation of heavy lift vehicles would require multiple stages - - but the upper stages would have to be designed with the mandates of the Air Force in mind. Since upper stages would probably need to be designed around the Air Force's Titan booster, the next generation of the Army's first stage would need to be able to accommodate the Titan's 120-inch wide frame.

What von Braun's team didn't know was that the Air Force was working on a secretly-designed second stage named Centaur. Centaur would be fueled with liquid hydrogen (LH2), the most efficient fuel known to rocket scientists. The problem with LH2 is that although it's efficient, it's not very dense, so the requirements for fuel tank sizes would be significantly larger than the original planned Titan upper stages. In order to accommodate the Centaur upper stage, the von Braun team's new first stage would need to support a 160" diameter frame.

The USAF Centaur was also supposed to power the X-20 Dyna-Soar space glider.
The Huntsville team managed to rework the design of their heavy lift booster to meet the new requirement by wrapping eight Redstone tanks around a central Jupiter tank assembly. The new vehicle, first named Juno V and then Saturn I, would launch with eight Rocketdyne H-1 engines capable of delivering a total thrust of 1.5 million pounds of force. The eight Redstone tanks, plus the Jupiter core were known technologies, so redesigns of new tanks and feed mechanisms weren't necessary. The slight weight disadvantage of multiple tanks had a tremendous offset in multi-year development costs that were avoided.
Wrap a Jupiter rocket with eight Redstones? That's a Saturn I.

 Barging In

 The Huntsville rocket scientist slapped together a Saturn I booster in no time, and ready for launch in early 1961. A static test at the Redstone Arsenal broke windows eight miles away from the test stand. The booster was too large to be transported by rail, so the Saturn would travel by barge to Cape Canaveral. In a pre-GPS world, the barge ran into some literal snags, as nautical maps were not accurate enough to note sand bars and shallows along the Gulf Coast route. After un-beaching the barge on several occasions, the Saturn I arrived at Pad 34 in August of 1961.
Heading for Cape Canaveral aboard the barge Compromise. Managed to beach itself four times.

One downside of the Huntsville crew's speed in construction was that the Air Force's upper stage (now called the S-IV) was nowhere near launch-ready in its development process. NASA decided to build a dummy upper stage, filling the large empty tank with water ballast equal to the proposed weight of the S-IV.
A working S-IV upper stage wouldn't be available for launch until 1964.
 On the morning of October 26th, 1961, the launch operations crew filled the nine tank assemblies with RP-1 kerosene and liquid oxygen. The only delay in the entire process was a brief hold for clouds and winds that would affect photography. After a one-hour delay, all holds were cleared, and the folks in the blockhouse ignited the eight solid propellent gas generator (SPGG) motors, that fired the liquid fuel pumps and started the H-1 engines. Saturn SA-1 lifted off the Pad 34 "milk stool" and headed out over the Atlantic, reaching an altitude of 84.6 miles only four minutes and nine seconds later. The water ballast accelerated to 3,611 mph before falling back to the ocean in an arc that stretched two hundred miles from Cape Canaveral.
We have liftoff, 27 October 1961, 12:30pm ET

Except for an early engine cutoff due to an underfilling of the tanks, the flight was flawless. The von Braun team displayed a mastery of heavy lift launch systems that would not be superseded by the Air Force ballistic missile group in building the way to the Moon landings.
After the success of SA-1, Saturn was the only way to the Moon for JFK.
 Pad 34 would become the initial platform for Apollo-Saturn development flights, and would provide key data for the follow-on Saturn V Moon ships. And all that work began fifty-one years ago today.
You can visit Pad 34 today on the Kennedy Space Center tour. The milk stool still stands.

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