Since the V-2 rockets of World War II, it’s been axiomatic in large rocketry that a flame deflector is necessary below booster engines to reduce the risk of damage to the launch pad and the booster.
The first launch of the SpaceX Starship used no deflector, and post-launch pad damage was extensive. Several booster engines failed shortly after launch, possibly as a result of debris, thermal and acoustic effects.
Future launches will likely feature a flame deflector, water deluge system, or both.
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Episode Transcript:
The launch - the first for the full Starship stack - represented the largest rocket assembly ever created on Earth, larger even than NASA’s Saturn V moon rocket. Investigations are still ongoing about the cause of the loss, which initially appears to coincide with vehicle staging, but it’s noteworthy that multiple booster engine failures were noted from lift off.
Significant damage to the reinforced concrete pad structure was observed, leading some to speculate that debris may have damaged the engines shortly after ignition while the vehicle was still on the pad.
Traditionally, large rockets have used a flame deflector below the engine exhaust to prevent flying debris and to address thermal and acoustic damage from main stage booster engines. Small flame deflectors were a component of even the relatively tiny V-2 missiles of World War II, and engine damage on the pad at ignition was a notable problem in early ICBM programs such as the General Dynamics Atlas.
A flame deflector bucket or trench, usually combined with a water deluge system, is a proven technology for eliminating this risk, and SpaceX is believed to have been designing a deflector at the time of the Starship launch.
In October of 2020, Elon Musk stated that his goal was to launch in Texas with no flame deflector, and commented that, “this could turn out to be a mistake.” While results of the test flight would seem to confirm that it was a mistake, there is a rationale behind an attempt to simplify launchpad operations. With a long-term SpaceX goal of making heavy lift launch almost as routine as airline operations, elimination of complex deflectors and water deluge systems would reduce costs, and if a long-range vision includes lift-off from places like the Moon or Mars, a simple pad or no pad at all is preferred.
Will Starship launch next time with a traditional flame deflector under the first stage? Barring a very expensive and lengthy redesign of the entire launchpad, it’s almost a certainty.