SpaceX FH : Falcon Heavy Demo : Feb 6, 2018 : Discussion Thread 2

[ArbitraryConstant]

Did it look to anyone else like the center core cut some/all of its engines around the time of booster separation, and re-lit them after?

my mistake, it's looking at the side booster

[spacetraveler]

Could this be due to the late in the window launch? That they had to trim the orbit and the coast time?

I'm not an expert, but I can't imagine there are that many constraints on when to raise a nonfunctional payload to an arbitrary orbit.

The burn was likely always going to take place at the same point in the orbit, so the orbit time might be a factor.

[Kabloona]

So Elon Musk reports a good second burn, but he said that the apogee was 7,000 km, which I believe is much different that we were expecting/guessing.  Now there will be, Elon says, a 5-hour coast before restart.  Interesting.  I'm not sure yet what that all means.

 - Ed Kyle

That puts the earth escape burn at perigee, where it is most efficient due to the Oberth effect, but at the end of a coast that's equal to the LEO to Geo coast of a GTO launch.  This demonstrates the extended coast time the Air Force needs to see for direct injection into Geo without putting the escape burn beyond the capabilities of the stage.

This was surmised by JCM many hours ago on the update thread. (Good luck finding it.  Everything is buried in posts.)

Yes, but JCM (and we) expected a 20,000 km apogee orbit with a period of 6 hrs and one orbit before TMI.

[abaddon]

My wild speculation is the hush hush on the center core is that it took out the ASDS. Wonder what it would take to sink one if a landing goes awry.

More likely they just want a little time between the otherwise successful mission and report of the loss of the center core.  You know, before the usual sources give us SPACEX LOSES CENTER CORE IN FIREY TEST FAILURE; SENATORS INQUIRE AS TO WHY THEY'RE SIGNED UP TO FLY CREW.

[tea monster]

You can hear on the soundtrack that the centre core is gone. I doubt it sunk the barge. They probably just didn't want to end the broadcast on a downer.

[Space Ghost 1962]

My wild speculation is the hush hush on the center core is that it took out the ASDS. Wonder what it would take to sink one if a landing goes awry.

Oh ye of little faith. OCISLY has taken many beatings and kept on ticking.

Think that there wasn't a clean separation on the left booster, which might have damaged a leg on landing, or perhaps something "bent" and the fine guidance couldn't remedy a deviation so it didn't encounter the barge well.

[Jim]

Elon just tweeted that the 2nd burn was to 7000km apogee, a significant raise but much less than GTO.

We didn't expect an actual GTO orbit, rather a 20,000 km apogee that would give a 6-hour orbit, with restart at perigee. But obviously not.

What is the period of a 7000km by 200km orbit?

[Kabloona]

Elon just tweeted that the 2nd burn was to 7000km apogee, a significant raise but much less than GTO.

We didn't expect an actual GTO orbit, rather a 20,000 km apogee that would give a 6-hour orbit, with restart at perigee. But obviously not.

Elon's five-hours of Van Allen Belt radiation might mean two ~200 x 7,000 km orbits, maybe?  I'm trying to figure the period of an elliptical orbit but my mind is buzzing right now. 

 - Ed Kyle

Yes, it must be at least 2 orbits.

[LouScheffer]

So Elon Musk reports a good second burn, but he said that the apogee was 7,000 km, which I believe is much different that we were expecting/guessing.  Now there will be, Elon says, a 5-hour coast before restart.  Interesting.  I'm not sure yet what that all means.

Two obvious possibilities.   250 x 7000 km is a 2.76 hour orbit.   Two of these is 5.5 hours, and this would maximize the Van Allen belt exposure, which Elon was stressing.

Less likely, he meant 250 x 17000.  That's a 5 hour orbit.

In either case, a shorter than 6 hour coast makes sense.  If you assume the 6 hour coast was planned for the center of the window, and they launched 1 hour after the center, then you need a 1 hour shorter orbit to get to the canonical injection spot.  If they had launched at the opening of the window, it would have taken a 1.25 hour longer coast to get to the right spot.

[Comga]

Congratulations to all concerned, except whoever set up the feeds, both of the lower images are pretty clearly the same booster...  But you're forgiven too!!!!

That was awesome. Thank you, SpaceX, for the most important launch of the 21st century, so far...

Did SpaceX get the trifecta? (all three boosters recovered)

The bottom views seems to be from the same booster. But if you look it closely, they are not identical. Looks like stereo camera to me.

It looked like a double display of a single camera. Even the cold gas thruster bursts were synchronized.
But if you looked close enough, the differenced started to show.
Unsynchronized grid fin motions, a delay between cold gas thruster bursts.
Not a stereo camera, but like one between bursts, with slightly different images.
SpaceX did not complete the most amazing launch in decades and make a silly error on the display.

[1]

Elon just tweeted that the 2nd burn was to 7000km apogee, a significant raise but much less than GTO.

We didn't expect an actual GTO orbit, rather a 20,000 km apogee that would give a 6-hour orbit, with restart at perigee. But obviously not.

What is the period of a 7000km by 200km orbit?

Back of the envelope calc puts the orbit at about 1.8 2.7 hours. So about three complete orbits, and TMI burn at perigee. More or less close to what we were expecting.

Edit: Messed up units. Corrected.

[Prettz]

If the center core didnīt make it (as some people are reporting) it actually just underlines that this was HARD! Too bad about the data they could have gotten from it, but... not important in the big picture.

Really too bad, lost all that wear data on the center core. I wonder why it didn't land, I would've thought that after the entry burn its descent is the same as any GTO mission.

Just because the landing was not successful does not mean all data was lost. It was likely returning telemetry for most of the flight.

Right but that's not the lost data I'm talking about. I mean what you get from inspecting an intact, upright stage. If its in pieces on the deck they might still get some useful info inspecting those, but I'm not an engineer.

[freda]

Starman live! 

[spacetraveler]

Good lighting.

[FDekker]

You can actually spot a part of the center core landing leg going into the drink at 38h:34m into the web cast. I'm quite sure.

[archae86]

SpaceX did not complete the most amazing launch in decades and make a silly error on the display.

I was almost willing to believe that until the end stage clearly showed both screens lined up on the same LZ.

Yes, I think there was a silly error.

[envy887]

Elon just tweeted that the 2nd burn was to 7000km apogee, a significant raise but much less than GTO.

We didn't expect an actual GTO orbit, rather a 20,000 km apogee that would give a 6-hour orbit, with restart at perigee. But obviously not.

Elon's five-hours of Van Allen Belt radiation might mean two ~200 x 7,000 km orbits, maybe?  I'm trying to figure the period of an elliptical orbit but my mind is buzzing right now. 

 - Ed Kyle

I'm getting 2 hours, 45 minutes for a 200x7000 km orbit (semi-major axis of 20,000 km). Sound about right?

[oiorionsbelt]

Is that Earth reflected in the helmet?

[meekGee]

There is the off-chance the center core could be floating Remember, it is extra-reenforced after all, so it has an even better chance of surviving the tip-over.

Not the way that camera got flung looking to the right.  That was not a good sign.

[Kabloona]

I'm getting 2 hours, 45 minutes for a 200x7000 km orbit (semi-major axis of 20,000 km). Sound about right?

You and LouScheffer agree on that (he said 2.76 hrs), so I'll take it you're both right.

That means 2 orbits, then burn at/near perigee, assuming Elon's "5 hour" coast quote was a ballpark.