I am new here. How is 'Orbit' defined? None of the filed flight plans have included a full orbit of the Earth. Does it need to complete more than 1 orbit to be resolved Yes?

@LarsOsborne Usually these kinds of questions are discussed at length in the comments. This one is, as well. Look for answers to other comments by the market creator

@LarsOsborne It needs to complete at least one full orbit.

@OlegEterevsky 2025*

@ProjectVictory Fixed, thanks!

I could kinda see them wanting to do it for IFT-5. They did prove raptor relight with the landing burn, after all.

I’m not sure. Engine relight in orbit is substantially different from the landing burn.

It is a bit, though in the EDA tour Elon half-jokingly said that this surely showed that raptor relight was fine even after all that.

In freefall you have different fluid dynamics in the tanks and all of the pipes.

They're using the header tanks in both cases which are full and pressurised with helium so it's not all that different, doesn't need ullage etc

Clearly, that's the idea behind the header tanks, but they haven't tested it. I'm not sure they are going to get a flight license for an orbital flight before they demonstrate the capability to control de-orbit.

They've tested it with Starship sideways in the bellyflop position. That's not gravity-vertical either.

I agree that it will likely work. (Though the test was aborted on IFT-3 for some reason.)

But if I were a regulator, and I was faced with licensing a flight with a new kind of engine on a huge rocket that is able to reach the Earth surface in one piece, I would likely require more definite proof.

I think it makes sense that they'd require more proof yeah, but I'm not 100% confident of that. But I think we mostly agree.

Ift-3 burn was probably canceled due to lack of attitude control.

I believe we have had confirmation that lack of altitude control was the reason (though I could be wrong, it was a little while ago)

Most rockets try to make orbit on their first flight so I think it's not obvious Starship will have to demonstrate a relight capability (although obviously the dynamic of having 'cancelled' such a demonstration is a real thing)

Most rockets also aren't designed to survive re-entry though

Sure, and Starship is much bigger. but at the same time, I don't think any of the first flight tests of capsules or systems that were designed to survive reentry used the near orbit profile outline.

That is a good point, though I'd argue that those spacecraft generally have more reliable deorbit mechanisms (eg lots of redundant thrusters of a relatively simple design whose performance in orbit is well characterised and who've been through tons of rigorous testing on the ground) than relighting a highly experimental rocket engine in conditions that it hasn't really been tested in yet.

I agree that it's not absolutely necessary, but all of the existing space capsules and second stages are an order of magnitude smaller than Starship.

Anyways, the market currently gives only 5% to August, while the probability of a flight before September is 86% from this market: /OlegEterevsky/when-will-starship-flight-5-happen . So I guess it is expected that SpaceX will do another suborbital flight.

IFT-4 Livestream "Starship orbital insertion"

@AlexLf7a4 "completes at least one full orbit" -- description

@OlegEterevsky this should be in the title then

@Berg I think this is a general understanding of "reach orbit". I don't want to make the title too verbose. It's easy enough to read a few lines of description to confirm the exact resolution criteria.

@OlegEterevsky not really. People generally agree that Yuri Gagarin has reached orbit, although he didn't complete a full revolution. Just replace the word "reach" with the word "complete".

@Berg Fair enough, I've changed "reach" to "complete"