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SpaceX is maybe, almost, someday, hopefully going to launch the Falcon Heavy rocket that SpaceX circus master Elon Musk expects to blow up shortly after launch. His concern is legitimate as SpaceX’s 27 engine-utilization is reminiscent of the Soviet’s disastrous failure of heavy-lift rockets of the early 1970’s that used 30 engines.

I hope it makes it far enough away from the pad that it does not cause pad damage. I would consider even that a win, to be honest.

Elon Musk

Three 1st Stage Heavy Rocket Engine Configurations: top – SpaceX Falcon Heavy, lower left – Soviet N1, lower right – NASA’s Saturn V

Soviet Heavy-Lift Plan: Lots of Engines

To get to the Moon the Soviet rocket engineers decided to use thirty engines on the first stage of their N1 rocket design. Smaller engines are easier to build and operate, but more engines mean more potential for failure.

A rocket engine is an effort to contain and control a continuous stream of explosive force. The power, heat, and stress of a rocket engine is unlike almost any other human-created machine. It is a complex network of plumbing, pumps, valves, and structure that must operate perfectly in synch. If they don’t it usually ends badly.

The Soviet’s N1 rocket design avoided the need of designing massive engines, like their counterparts in the United States, however, they didn’t anticipate the complexities of all engines operating in concert. The result was four failures in four launch attempts and the cancellation of the Soviet Moon program. One failure happened at the launch pad with the power of a small nuclear bomb. 

Killer Vibrations

Even if every engine works to perfection, the vibrations caused by each engine can literally shake a rocket to pieces. NASA engineers learned early in the space program that vibrations between the engines and the aerodynamic stresses on the rocket created a ‘pogo‘ vibration running up and down the length of the rocket.

They thought they understood the issue until Apollo Six partially failed because of pogo vibration issue. During the ascent phase of the launch, vibrations damaged fuel lines on the second and third stages. The damage caused the rocket’s second stage to shut down two of the five engines prematurely, and the third stage engine failed to ignite.

Saturn V’s Five Heavy-Lift Engines

Despite the issues with pogo oscillations, NASA’s five Rocketdyne F-1 engines on the Saturn V Moon rocket resulted in 13 out of 13 successful first stage launches. The only partial failure came on Apollo 6 after the first stage had completed its boost of the second and third stages.

It is unclear why the successful Apollo program engine configuration has been rejected as an option for contemporary heavy-lift rockets. It is probable that private ventures into space operations, like SpaceX, want to save money by designing only one rocket engine for all uses.

SpaceX 2017 Great, 2018?

SpaceX is coming off a spectacular year. Of 18 launch attempts, SpaceX had 18 successful launches. SpaceX also had a perfect relanding record in 2017 for every attempt.

2018 is not starting out as well. SpaceX has only had one launch so far this year and it is rumored that the payload did not make it into orbit. No public information has been made about the success of the launch because it was a highly valued, super-secret satellite. It is so secret that the public has not even been told who the satellite was built for, or its general purpose.

SpaceX has proclaimed that its launch vehicle did everything it was designed to do, but the launch narration indicates that there might have been an issue when the fairing or cover around the satellite was supposed to deploy. The launch narrator paused for ninety seconds after he said the fairing would deploy “any second now.” When he began talking again he changed the subject. A few seconds later he finally confirmed the fairing had deployed but did not explain the delay in deployment.

SpaceX Falcon Heavy Engine Roulette

So far, the Falcon Heavy rocket is not a bright spot in the SpaceX story. Its first launch was planned for 2013, and for multiple reasons, it has been delayed for five years. It had been rescheduled for launch in late Fall of last year but was then delayed again. On 1 December Musk tweeted:

Falcon Heavy to launch next month from Apollo 11 pad at the Cape.

Elon Musk

To date (21 January 2018) the Falcon Heavy has still not had a test fire of its first stage engines. This means there are less than ten days to launch test the engines and then prepare the rocket for launch. Any issues during the test firing and the launch schedule will likely slip again into February.

If SpaceX has a successful launch it will still have to prove the reliability of the 27 engine design. The mass-numbers-of-engines design ultimately killed the Soviet program with four consecutive failures. SpaceX is reliant on business customers who have faith in their ability to deliver their payload into orbit. Continued delays and any failure will reduce confidence in the Falcon Heavy, risking it to have the fate of the Soviet N1.

(Story Update:  SpaceX had a successful test firing of the Falcon Heavy first stage booster today – 24 January 2018.)