SpaceX Starship : First Flight : Starbase, TX : 20 April 2023 - DISCUSSION

[sebk]

There's simply no way to have single burn launch to 235km apogee and do 3/4 of the whole circle with perigee below the sea level. Perigee must be around 50km up.

Not true. You can have perigee points below sea level and achieve a very high apogee.

Yes. High is a keyword here. To get perigee below the sea level and do 3/4 of the circle you have to have your apogee above 280320km. Starship will have apogee of 235km. This makes below SL perigee impossible.

[sferrin]

Doesn’t sound or look great:

Wonderful.  Now OSHA will shut it down for three weeks for an "investigation".

[eriblo]

Discussion about suborbital/orbital or not first need to decide on the definition of orbital as there is not one that is obvious and universally used.

Some candidates:

Specific energy >= -μ/2R (lowest circular orbit above the surface).
Specific energy >= -μ/2r for some r>R.
Perigee above surface.
Perigee above some height h.

r and h could be 50 km, 80 km, 100 km or some spacecraft dependent value guaranteeing more than a full orbit is possible.

[FutureSpaceTourist]

Another view of the tower issue earlier:

https://twitter.com/csi_starbase/status/1647215514186334208

Here is another angle showing what appears to be some kind of electrical short  resulting in an object falling into the base of the tower.

🎥@LabPadre

At least it seems far enough away from Starship to not have damaged it.

[sferrin]

And there it is. Wonder if it was the elevator.  Launch ain't happening this week.   

[Ben Baley]

Doesn’t sound or look great:

 

Any more info on what happened?

This is concerning for a few reasons, even a small object falling that distance could easily damage the systems on the launch tower, and there's the risk to anyone working below, the last thing we want to see is having the flight delayed for an OSHA investigation.

[jimvela]

If that's the elevator, it is hard to believe the tower would be fully usable for a launch attempt with it out of service- even if there wasn't anything else damaged during the event.

It will be interesting to see how much activity there is around the tower in the next couple of days.

[FutureSpaceTourist]

https://twitter.com/spmttracker/status/1647228303542046725

Appears to be the elevator failing, they are using manbaskets to bring people up to the SQD level.

[Slothman]

It did sound like more than an "electric short" but not massive enough for an elevator or counterweight/chopstick sled coming down (I remember when they were just putting those on, one of them fell down taking parts of scaffolding with it). Maybe like some electric circuit box or battery fell off the wall, no idea what they got up there. Bad enough, but really didn't sound like something 1ton+ in mass.

But perception can be deceiving especially not knowing from which distance the audio was taken. There was certainly a thud at the end

[pedz]

What does the green text say up in the right top corner?

I'll be on Long Island probably or I might go over to the Fisherman Statue.

[minusYcore]

Discussion about suborbital/orbital or not first need to decide on the definition of orbital as there is not one that is obvious and universally used.

Some candidates:

Specific energy >= -μ/2R (lowest circular orbit above the surface).
Specific energy >= -μ/2r for some r>R.
Perigee above surface.
Perigee above some height h.

r and h could be 50 km, 80 km, 100 km or some spacecraft dependent value guaranteeing more than a full orbit is possible.

US Federal definition of suborbital is a trajectory whose vacuum instantaneous impact point does not leave the Earth's surface. Mount Everest is under 9km tall, so a rocket with perigee of >9km (worst case) is orbital (or one way to deep space).

https://www.law.cornell.edu/uscode/text/51/50902#24

[sebk]

The orbit here is about 50x235km it's perigee is above surface level, but within the atmosphere. And energetically it's equivalent to 142x142km circular orbit which for a vehicle the size and mass of Starship would decay in significantly more than once around (less streamlined and with lower ballistic coefficient SkyLab started it's last full circle at ~135km)

The whole flight is within the atmosphere, which reaches much higher than 235 km. Therefore the notion of Starship "entering atmosphere" at some  point on this flight does not make sense.

This is a useless semantic game. By that logic International Space Station is not a space station at all. And none of the satellites in LEO is in space. In fact even GEO is doubdful as the traces of Earth's atmosphere stretch above 100000km.

And for practical spaceflight purposes reentering atmosphere is defined as passing entry interface which happens at 120 to 130km up. i.e. at the altitude where effects of the atmosphere like heating are large enough.

And orbital velocity is only horizontal velocity. A hyperbolic suborbital flight that has the same kinetic energy like some circular orbital flight is still a suborbital flight.

Wrong. Doubly so.

1. Elliptic orbits do have significant vertical components except at peri- and apo-apses.

2. Hyperbolic flight is never suborbital. All suborbital flights are elliptic.
 

Can you please quote the source for the 50 km perigee?

Jonathan McDowell estimated it at 50km.

But this actually comes from pretty basic geometric considerations and requirements for rocket burnout to happen above the commonly understood atmosphere. See below.

There's simply no way to have single burn launch to 235km apogee and do 3/4 of the whole circle with perigee below the sea level. Perigee must be around 50km up.

This is totally wrong.

Nope. You are totally wrong.

To have perigee below sea level and be able to do 3/4 of the circle around the Earth after standard rocket launch (Space-guns, X-30 NASP-like spaceplanes or other Sci-Fi solutions notwithstanding)  you must have apogee at ~320km or higher. Otherwise your trajectory would be too shallow.

Rocket's SECO must happen at least 80km up (realistically it'd be 120+, but let's get to the extreme) or it will fall down without even crossing the Atlantic.  If you want your perigee to be the lowest possible and you're flying 3/4 around the globe, at SECO you should insert into an orbit about 1/8 of the circle (45°) past the perigee. And you're 80km up. If the perigee is 0, then from the simple geometry apogee would be more than 4x80 i.e. 320km (it would be 320km if the orbit were exactly circular, but such would be non-physical, as it must be slightly elongated, so it's in fact more than 320km.

Starship published apogee is 235km. To keep perigee at 0 the SECO would have to happen at... 59km. That's totally unworkable.

Realistically even 50km is somewhat low. With 235km apogee it would mean SECO at 96km which would be low but not impossibly (I didn't see SECOs happening below 115km).

[Alvian@IDN]

If that's the elevator, it is hard to believe the tower would be fully usable for a launch attempt with it out of service- even if there wasn't anything else damaged during the event.

It will be interesting to see how much activity there is around the tower in the next couple of days.

Manlifts can still be used for access which they're doing it right now

Once again a classic "let's put the delay speculation as a fact"

[sanman]

The changes to the flight plan may be to eliminate some minor issues that SpaceX feels the FAA is still not satisfied with.

Nope, that's not it. When Gwynne took over some months ago SpaceX did a thorough review of this test flight. Since then a number of test objectives have been moved from this test flight to future ones.

But, why? Flip & landing was already demonstrated by SN15. What was wrong about leaving this maneuver in the flight plan? 

Planning for it requires software validation, flight dynamics and CFD simulations, and who knows how much other testing and preparatory work. That all takes time and resources away from work on earlier, more significant milestones for this first flight test.

Are you sure that's the long and the short of it? What if they did attempt that tailsitter flip landing maneuver without the preparatory work? They'd be no worse off than the current scenario where they don't attempt it at all. After all, the flip maneuver is taking place at the tail end of the descent anyway. So I don't see what they have to lose by attempting that flip maneuver, even without the preparatory work. Just do it the exact same way you did it for SN15, if need be.

[sferrin]

They're going to have to inspect everything along the path of whatever fell.  Propellant and electrical to Starship, structural members, everything around and below the impact site and THEN repair whatever it was that broke.  With no elevator.

[Herb Schaltegger]

The changes to the flight plan may be to eliminate some minor issues that SpaceX feels the FAA is still not satisfied with.

Nope, that's not it. When Gwynne took over some months ago SpaceX did a thorough review of this test flight. Since then a number of test objectives have been moved from this test flight to future ones.

But, why? Flip & landing was already demonstrated by SN15. What was wrong about leaving this maneuver in the flight plan? 

Planning for it requires software validation, flight dynamics and CFD simulations, and who knows how much other testing and preparatory work. That all takes time and resources away from work on earlier, more significant milestones for this first flight test.

Are you sure that's the long and the short of it? What if they did attempt that tailsitter flip landing maneuver without the preparatory work? They'd be no worse off than the current scenario where they don't attempt it at all. After all, the flip maneuver is taking place at the tail end of the descent anyway. So I don't see what they have to lose by attempting that flip maneuver, even without the preparatory work. Just do it the exact same way you did it for SN15, if need be.

Feel free to explain that to Gwynne Shotwell, the flight test operational planning team and the FAA. Because they are pointedly NOT doing that, they are belly-flopping, assuming the vehicle survives its “passive re-entry” as described in the 122 page Written Re-Evaluation document filed by the FAA last night. They are also expending the Ships for flights 2 and 3 by tumbling during entry to ensure breakup prior to attempting a landing.

But I’m sure your reasoning will be compelling enough to make them toss out their well-laid plans and just wing it.

[minusYcore]

The changes to the flight plan may be to eliminate some minor issues that SpaceX feels the FAA is still not satisfied with.

Nope, that's not it. When Gwynne took over some months ago SpaceX did a thorough review of this test flight. Since then a number of test objectives have been moved from this test flight to future ones.

But, why? Flip & landing was already demonstrated by SN15. What was wrong about leaving this maneuver in the flight plan? 

Planning for it requires software validation, flight dynamics and CFD simulations, and who knows how much other testing and preparatory work. That all takes time and resources away from work on earlier, more significant milestones for this first flight test.

Are you sure that's the long and the short of it? What if they did attempt that tailsitter flip landing maneuver without the preparatory work? They'd be no worse off than the current scenario where they don't attempt it at all. After all, the flip maneuver is taking place at the tail end of the descent anyway. So I don't see what they have to lose by attempting that flip maneuver, even without the preparatory work. Just do it the exact same way you did it for SN15, if need be.

If flip and landing worked, they would need to dispose of the ship. Instead, they are keeping 14 metric tons of propellant as ballast and planning for the ship to explode on impact and sink.

[FutureSpaceTourist]

What does the green text say up in the right top corner?

It says: designated viewing zone for mariners

Clearer image attached

[edzieba]

Nope. You are totally wrong.

To have perigee below sea level and be able to do 3/4 of the circle around the Earth after standard rocket launch (Space-guns, X-30 NASP-like spaceplanes or other Sci-Fi solutions notwithstanding)  you must have apogee at ~320km or higher. Otherwise your trajectory would be too shallow.

Wrong. Impossible for a pure impulsive launch (e.g. space gun) but not for any real launch vehicle, which has tens of minutes of burn time, and outside the atmosphere can vector thrust arbitrarily. Whilst eccentricity and plane changes performed within the burn to orbit are expensive in terms of delta V, physics will not stop you. You can - for example - insert directly into an orbit with an apogee above your current altitude and descending, and thus never reach apogee.

[jimvela]

If that's the elevator, it is hard to believe the tower would be fully usable for a launch attempt with it out of service- even if there wasn't anything else damaged during the event.

It will be interesting to see how much activity there is around the tower in the next couple of days.

Manlifts can still be used for access which they're doing it right now

Once again a classic "let's put the delay speculation as a fact"

Manlifts can be used for access, as we are seeing.

They would not be adequate for any day-of-launch tower activities, nor will inspection and repair access for the tower be quick -if- that was the elevator falling and thus man lift or crane access is the best they can do.

I speculated that the tower might not be usable for a launch event in the near term -if- the elevator fell.
That long drop with sparks and the thud at the end at least represents a reasonable possibility as an elevator failure/fall event. 
It is certainly not clear what happened.

I did not speculate further on repair / recovery actions and on what timeline. 
I noted that it will be interesting to observe the response over the next couple of days.

If I were to speculate further, it would be:
+ if the elevator fell, I speculate that the launch attempt will not happen in the coming week.  Multiple practical reasons.  I could be proved very wrong.
+ if it wasn't the elevator that fell, and whatever it was can be easily repaired, then we should know that before end of day Sunday. 
+ if it wasn't the elevator that fell, I'm still very skeptical that a Monday launch attempt is still in the cards for an event where they are clearly unable to access the tower with the elevator.  There's no way a not-functional elevator would be a valid state for the launch support equipment during a launch attempt.
+ I bet this picks up the discussion volume considerably over the weekend.