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Could the Sea Dragon light it's main engines once it is airborne, or is it too big?

Modern submarine launched missiles use compressed gas and the buoyancy of the missile to propel the missile out of the water. The missile's main engine then ignites once it is airborne.

While the Sea Dragon is not launched from a tube, the ballast unit could pull the rocket down, and high pressure gas could be released into the engine bell to help propel the rocket out of the water.

The advantage of an airborne ignition is that it would be far less deadly to sea life. Shock waves travel very efficiently underwater, but most of the energy from an airborne explosion is lost at the air water interface.

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    $\begingroup$ How would it get airborne without lighting its main engines? Sea Dragon wasn't planned to launch from a tube. $\endgroup$ – Organic Marble Dec 14 '20 at 21:06
  • $\begingroup$ Once we make edits in response to a specific helpful comment, it's usually good practice to reply to the comment with a short message like "thanks, edited." or "I've made an edit, how does it look?" Sometimes a user will then delete their comment in response, and sometimes this will prevent close votes from being cast. Don't forget to use the @ so that the user receives a notification that you've responded. Thanks! $\endgroup$ – uhoh Dec 15 '20 at 0:30
  • $\begingroup$ Another thing to consider is the expansion ratio of the engine- its already over-expanded at sea level, but the ambient pressure deep in the ocean, I would imagine, would severley over-expand the exhaust and create immense accaustic instabilities. This could have been what the outboard engines were designed for though, to act as an intermediate stage inbetween the rise in buoyancy, and the main engine. $\endgroup$ – Reuben Farley-Hall Dec 15 '20 at 1:16
  • $\begingroup$ @OrganicMarble I've clarified the question. $\endgroup$ – UEFI Dec 15 '20 at 9:01
  • $\begingroup$ Releasing enough 'high pressure gas into the nozzle' to lift that monster out of the waters sounds impractical at best, or like it would have similar effects to lighting the engine. Do you have any calculations as to what it would take to do that? $\endgroup$ – Organic Marble Dec 15 '20 at 13:59

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