How can SpaceX receive data from Starship during re-entry communications blackout

Question

Surviving re-entry will be one of the initial critical aspects of the Starship development program.

If there are locations on the vessel where the heat-shield fails, leading to its destruction how would SpaceX be able to receive any data during this phase of flight to diagnose the failure? I understand that radio communications are not possible when the ship is surrounded by plasma.

Do you want to exclude other ways of receiving data, like a "black box recorder"? If you'd like to allow for answers that mention methods other than telemetry, you can change "telemetry" to "information". Different but related: Will Red Dragon experience a “Communications Blackout” during SRP? and How long did the plasma blackouts of Perseverance's signals to MRO and direct-to-Earth last during its seven minutes of terror? which discusses that different frequencies may have different blackout time — uhoh, Aug 09 '21 at 02:12
@uhoh Any way of getting the data is OK. I wasn't aware that Flight Data Recorders (Black boxes) are used in rocketry, but I guess there is no reason why not. — Mike H, Aug 09 '21 at 02:25
Since readers don't always check the comments, it might be a good idea for you to edit and modify your question to allow for non-telemetry answers. As it reads right now it asks only for telemetry during blackout, which as-written may not allow for much of an answer since blackout means no radio communications and telemetry via optical communications is not yet a thing. Would plasma sheathes from reentry heating block optical/UV communications as well as radio? — uhoh, Aug 09 '21 at 02:36

score 4 · Accepted Answer · answered Aug 09 '21 at 11:53

Surviving re-entry will be one of the initial critical aspects of the Starship development program.

According to a statement by Elon Musk during his recent interview with Tim Dodd (Everyday Astronaut), they are not worried about re-entry yet. Elon Musk said they don't really know whether they will even get to space, let alone orbit. It is entirely possible that the vehicle breaks up on ascent. In fact, he said, he would consider anything that does not destroy the pad a success.

If there are locations on the vessel where the heat-shield fails, leading to its destruction how would SpaceX be able to receive any data during this phase of flight to diagnose the failure?

It is not necessary to receive data during this phase of flight to diagnose the failure. There's no deadline, they can just as well receive the data a bit later, e.g. from a flight recorder.

Also, a lot can be reconstructed by inspecting the wreckage, if they really wanted to go to the trouble of doing that.

I understand that radio communications are not possible when the ship is surrounded by plasma.

It is not necessarily surrounded by plasma. The shockwave will be in front of the vehicle (where "in front" means "roughly along the velocity vector"), and that's where the highest concentration of plasma will be.

So, there is a good chance that they will still be able to send data "up", just not "down". As it so happens, there are about 1200 SpaceX-owned communication satellites in a low earth orbit, plus they have access to NASA assets.

That's what the Space Shuttle Orbiter did in the later years, for example. Instead of communicating through the plasma to the ground, it threaded the needle through a "hole" in the plasma created by the airflow around its body upwards to the TDRSS network.

Do you know if flight data recorder have been proposed? The recovery effort to retrieve black boxes from aircraft crashed in the ocean is usually a substantial and expensive exercise. — Mike H, Aug 09 '21 at 21:05
@MikeH One key problem with regard to recovering aircraft flight data recorders is knowing where the aircraft went down. That will not be a problem with regard to a hypothetical failed Starship reentry. — David Hammen, Aug 10 '21 at 00:51
@MikeH I have worked with multiple reentering spacecraft. All of them have carried flight data recorders. The flight data recorders can record a lot more data (a whole lot more data) than can possibly be downlinked. — David Hammen, Aug 10 '21 at 00:55
"As it so happens, there are about 1200 SpaceX-owned communication satellites in a low earth orbit..." Hmmm... coincidence? ;-) There's also your potentially related answer — uhoh, Aug 10 '21 at 14:58
@David Hammen Thanks for that, I had assumed that the difficulty of recovery of flight data recorders from the sea would have limited their use in rocketry, where unlike aviation, every flight ended in a crash. (excluding SpaceX) — Mike H, Aug 10 '21 at 21:36
@uhoh: You could write a whole essay about coincidences when it comes to SpaceX. What do you need to explore Mars? Electric vehicles. Oops. Tesla. What's the best way to quickly build radiation shielded habitats? Dig underground. Oops. The Boring Company. Also, what does Elon Musk's brother do again? Containerized hydroponic greenhouses. — Jörg W Mittag, Aug 11 '21 at 10:57

score 3 · Answer 2 · answered Aug 09 '21 at 11:27

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The blocking caused by re-entry plasma is not uniform, they can communicate "up" through starlink, that is probably part of the reason why they mounted starlink dish on sn15 flight.

answered Aug 09 '21 at 11:27

Szymon Marciniak

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How can SpaceX receive data from Starship during re-entry communications blackout

2 Answers2