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

[chopsticks]

Doesn’t sound or look great:

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

Please stop with your conspiracy theories.

[minusYcore]

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.

In terms of Starship though, that isn't happening. It has one ascent acceleration phase and no powered descent acceleration.

Starship: For the first launch, after ascent engine cutoff, Starship would vent residual main tank propellant during the in-space coast phase of the launch at or above 120 kilometers AGL.
Following the in-space coast phase, Starship would begin its passive descent.

[sferrin]

Doesn’t sound or look great:

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

Please stop with your conspiracy theories.

Sorry if reality triggered you.  No way anybody is just going to crack a beer and give a thumbs up for Monday after something like that. 

[kdhilliard]

To have perigee below sea level and be able to do 3/4 of the circle around the Earth after standard rocket launch ... you must have apogee at ~320km or higher. Otherwise your trajectory would be too shallow.

... for example - insert directly into an orbit with an apogee above your current altitude and descending, and thus never reach apogee.

Sure, but your example trajectory would have its perigee <1/2 an orbit away from SECO, right?

[Lee Jay]

Is there some reason to believe whatever fell is the elevator?  It's almost impossible for an elevator to fall.

Something can fall down the shaft and damage the elevator, but having the whole car fall is protected against by like octuple redundancy.

[sferrin]

Is there some reason to believe whatever fell is the elevator?  It's almost impossible for an elevator to fall.

Something can fall down the shaft and damage the elevator, but having the whole car fall is protected against by line octuple redundancy.

Somebody else suggested elevator counterweights. (Which makes more sense given how solid the final impact sounded.)  In either case though it's because of the location of what was visible.  What else goes that high up the center of the tower and is that heavy?

[minusYcore]

To have perigee below sea level and be able to do 3/4 of the circle around the Earth after standard rocket launch ... you must have apogee at ~320km or higher. Otherwise your trajectory would be too shallow.

... for example - insert directly into an orbit with an apogee above your current altitude and descending, and thus never reach apogee.

Sure, but your example trajectory would have its perigee <1/2 an orbit away from SECO, right?

I believe they are speaking of a non-Hohmann orbit burn. So rather than applying deltaV at perigee/apogee perpendicular to the major axis, they raise both nodes simultaneously by accelerating at, for example, the midpoint with thrust parallel to the major axis.

[launchwatcher]

Is there some reason to believe whatever fell is the elevator?  It's almost impossible for an elevator to fall.

Something can fall down the shaft and damage the elevator, but having the whole car fall is protected against by line octuple redundancy.

Somebody else suggested elevator counterweights. (Which makes more sense given how solid the final impact sounded.)  In either case though it's because of the location of what was visible.  What else goes that high up the center of the tower and is that heavy?

I don't have a good sense of the mass of the object(s) that fell.

Pure speculation: it could be something not intended to be permanently part of the tower, like tools/equipment temporarily positioned in the tower for work.  Rolling tool chest, gas cylinders for welding, etc., that got away from workers clearing the tower ahead of Monday's launch window.

[eriblo]

To have perigee below sea level and be able to do 3/4 of the circle around the Earth after standard rocket launch ... you must have apogee at ~320km or higher. Otherwise your trajectory would be too shallow.

... for example - insert directly into an orbit with an apogee above your current altitude and descending, and thus never reach apogee.

Sure, but your example trajectory would have its perigee <1/2 an orbit away from SECO, right?

I believe they are speaking of a non-Hohmann orbit burn. So rather than applying deltaV at perigee/apogee perpendicular to the major axis, they raise both nodes simultaneously by accelerating at, for example, the midpoint with thrust parallel to the major axis.

The discussion is about the orbit that Starship follows after the insertion burn ends until it reenters the atmosphere (assuming no further burns).

By comparing to a circle it should be fairly obvious even without doing any math that for a majority of the orbit to be above a certain altitude the highest point must be much higher above this altitude than the lowest point is below it.

Example: Take a LEO at 120 km altitude. Shift it to one side by 120 km. It is now a reasonable approximation for an orbit with a 0 km perigee and a 240 km apogee and only half of it is going to be above 120 km.

[Jim]

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

Doesnt have be OSHA.   SpaceX could do it themselves

[alastairmayer]

[...] Just do it the exact same way you did it for SN15, if need be.

They can't. S24 hardware is different from SN15 hardware, so they'd have to re-write the control software. There's no point in doing that for this test, since later ships have different hardware from S24.

[Jim]

orbital flight with making less than one orbit

[alastairmayer]

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

Please stop with your conspiracy theories.

So, where was the ULA sniper positioned? 

[ThatOldJanxSpirit]

orbital flight with making less than one orbit

Jim, you are well aware how small the delta is.

[llanitedave]

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

Please stop with your conspiracy theories.

So, where was the ULA sniper positioned? 

Shocking reveal:  It was Tim Dodd all along.

[Lee Jay]

Is there some reason to believe whatever fell is the elevator?  It's almost impossible for an elevator to fall.

Something can fall down the shaft and damage the elevator, but having the whole car fall is protected against by line octuple redundancy.

Somebody else suggested elevator counterweights. (Which makes more sense given how solid the final impact sounded.)  In either case though it's because of the location of what was visible.  What else goes that high up the center of the tower and is that heavy?

A counter weight was my first thought.  It's generating so many sparks that it's hard to believe it's a box or something falling and hitting things.  More like sliding.  And a counter weight doesn't have all the protections a car does.

I had to commission a custom elevator once.  One of the last things we had to do was put 133% of the car's rated load in the car, and "cut the cables" (we didn't actually cut them, we just released them).  The car fell about an inch or two before the brakes caught it.  And oh boy, was getting them to release after re-attaching the cables a fun time.  Take all the load off and start the wrestling match.

[jon.amos]

Pure speculation but those sparks look electrical to me.  Could someone have lost control of or otherwise caused a running genset used for weldinng to fall?  We know they are welding at height and local generator makes more sense than permanently installed power to support.

[plank]

I wonder if SpaceX Will attempt to catch Starship upper stage in the future?  The reason I say this is because of the way they word it on the website.  Only mentioning catching Super heavy and not Starship.

[Lee Jay]

Pure speculation but those sparks look electrical to me.  Could someone have lost control of or otherwise caused a running genset used for weldinng to fall?  We know they are welding at height and local generator makes more sense than permanently installed power to support.

It does?  On a tower that size with that many already-existing high-power devices (winches, hydraulics, and so on), it makes more sense to me to put outlets everywhere for this sort of thing (i.e. 480V three-phase 100A Hubbells or similar).  Where I work, we have them all over the place, including on towers way smaller than this one.

[edzieba]

Gentlemen, please: the OLIT has stairs. Even if whatever falling doodad prevents use of the elevator, do you really think there are no SpaceXers willing to risk thigh chafing to perform any tasks out of manlift reach in order to avoid a delay?