SpaceX Falcon Heavy : Arabsat 6A : LC-39A : April 11, 2019 - DISCUSSION

[crandles57]

John Insprucker just stated apogee of 90,000 km. I guess that means little or no inclination change.

Nope...they are going from 27 to 23 also.

What is the equivalent mass to LEO? Is it over 20,000kg?

I am asking to check if 3 boosters reusable config has proven it is a "Heavy-lift_launch_vehicle"

for
https://en.wikipedia.org/wiki/Heavy-lift_launch_vehicle

[stcks]

Heard over the countdown net "Load limiting shutdown." and a while later "2nd load-limiting shutdown" before BECO, looks like they are shutting down booster engines to limit G-loads prior to BECO-proper.

Yes, I noticed this too. It was quite interesting. I rewatched the SpaceX stream this morning and here are my notes:

T+1:35: net callout <unintelligible> "shutdown". can't tell any change of plume based on webcast
T+1:43: noticeable up and down oscillations on booster cams, JI call out "we've begun dropping power on the side boosters"
T+2:04: large oscillation corresponding with net callout "second load limiting shutdown"
T+2:09: oscillations stop

[Brovane]

Elon tweeted in a reply "Recovered from water, but undamaged", so it looks like they have decided they can reuse them after splashing down, at least in some cases.

https://twitter.com/elonmusk/status/1116514534557016064

I'll bet they feel a little silly for the attempted catches, now that they know they are basically boat hulls.

Fun launch to watch!

"You don't learn anything from success, but you learn a lot from your failures" 
SpaceX President and COO Gwynne Shotwell 

[Alexphysics]

If they indeed shut down the engines before BECO, it would show up on the telemetry data. Now we only need someone to take the time to collect all the data and put into a graphic...

[stcks]

A few fun clips from this mission that I didn't notice watching it live.

T+2:51: side booster boostback startup visible from other booster cam
T+3:10: center core plume clearly visible looking aft on side booster

[Vettedrmr]

Yes, but surely SpX can vary the duration of the re-entry burn to manage the speed; that's my question.  And I expect that this burn would (should?) be longer than normal burns due to the higher velocity at MECO.  Maybe just by a few seconds, but longer.

Or am I just missing the concept?

Have a good one,
Mike

[crandles57]

Yes, but surely SpX can vary the duration of the re-entry burn to manage the speed; that's my question.  And I expect that this burn would (should?) be longer than normal burns due to the higher velocity at MECO.  Maybe just by a few seconds, but longer.

Or am I just missing the concept?

Have a good one,
Mike

If fuel was unlimited, you could slow them down to a certain speed before hitting atmosphere and all booster landings would be same stress/toastiness.

However fuel isn't unlimited. If a challenging mission, you want atmosphere to do as much of the work of slowing down the booster as possible without booster getting too hot in order to conserve the amount of fuel needed, at least on missions that are payload mass challenging and/or on GTO & faster missions. The more challenging the mission the more work is left to atmosphere and booster gets toastier.

[ugordan]

If they indeed shut down the engines before BECO, it would show up on the telemetry data. Now we only need someone to take the time to collect all the data and put into a graphic...

There's an obvious relaxation of the booster attachment points visible at the point when "2nd load-limiting shutdown" was announced so it should be noticeable in telemetry as well as it's likely the side cores were at that point already running at the lowest possible thrust setting so it should show up as a nice step change in accel.

I pointed out a year ago that the inaugural FH also seemed to shut down at least one engine on each booster 3 seconds prior to BECO (check out timestamp 32:24 in the countdown net audio version of the FH webcast "M7 shutdown... side boosters") and there was a distinct visual puff at the edges of the side cores visible from the ground at 2:53 in this great video: .
Engine 7, coincidentally, is one of the outermost two engines on each side core so that matches up. At the time I was told I probably misheard the audio net (which has been shown to happen in retrospect...).

What's more curious is on this launch something about an engine shutdown ("<unintelligible> limiting shutdown"?) was called out as early as around T+1:30 into the flight and the 2nd shutdown was announced at roughly T+2:04.

I'm curious what our resident flight dynamics analysts will show for G loads during various phases of ascent, I imagine they'd be substantial near BECO and would drive the 2nd shutdown to limit the payload max G envelope, but I'm curious why the first one happened so soon.

[rsdavis9]

I thought I heard limiting stresses on center core for the first one.
This would make sense as nearly empty side boosters transmit more force to the center core.
So if this is true then it would seem we could get more out of falcon heavy by further strengthening the center core. Or maybe spacex is not pushing the center core structure and attachments to their design limits yet.

[edkyle99]

Terrific launch for SpaceX, and at a key moment with NSSL and NASA's SLS frustration underway. 

I have only one note about the news coverage.  Repeatedly, it is written that Falcon Heavy is "the world’s most powerful operational launcher", etc., which technically is true in terms of liftoff thrust, but FH-2 only put 6,465 kg into GEO-1500-ish m/s.   That's only 64% or so of what Ariane 5 ECA has boosted to an equivalent orbit.  All of that thrust is neat, but much of it is not being used for the actual payload mission.

 - Ed Kyle

[rpapo]

Terrific launch for SpaceX, and at a key moment with NSSL and NASA's SLS frustration underway. 

I have only one note about the news coverage.  Repeatedly, it is written that Falcon Heavy is "the world’s most powerful operational launcher", etc., which technically is true in terms of liftoff thrust, but FH-2 only put 6,465 kg into GEO-1500-ish m/s.   That's only 64% or so of what Ariane 5 ECA has boosted to an equivalent orbit.  All of that thrust is neat, but much of it is not being used for the actual payload mission.

 - Ed Kyle

Ariane is a throw-away rocket.  If FH were being tossed, it could throw a lot more into orbit too.  Of course, it would probably need a stronger payload adapter too.  And a bigger fairing.

Though I agree with you about how they are spinning this.  It is somewhat overblown.

And then there's the "It's the first time they recovered all three boosters!" stuff.  First time, yes.  But only the second try.

[mn]

Terrific launch for SpaceX, and at a key moment with NSSL and NASA's SLS frustration underway. 

I have only one note about the news coverage.  Repeatedly, it is written that Falcon Heavy is "the world’s most powerful operational launcher", etc., which technically is true in terms of liftoff thrust, but FH-2 only put 6,465 kg into GEO-1500-ish m/s.   That's only 64% or so of what Ariane 5 ECA has boosted to an equivalent orbit.  All of that thrust is neat, but much of it is not being used for the actual payload mission.

 - Ed Kyle

If you expended all 3 cores, (and enlarged the fairing, strengthened the payload adapter) how much can the FH boost to the same orbit? if it's more than Ariane 5 ECA then 'the world's most powerful launcher' is a fair statement.

[Ultrafamicom]

Terrific launch for SpaceX, and at a key moment with NSSL and NASA's SLS frustration underway. 

I have only one note about the news coverage.  Repeatedly, it is written that Falcon Heavy is "the world’s most powerful operational launcher", etc., which technically is true in terms of liftoff thrust, but FH-2 only put 6,465 kg into GEO-1500-ish m/s.   That's only 64% or so of what Ariane 5 ECA has boosted to an equivalent orbit.  All of that thrust is neat, but much of it is not being used for the actual payload mission.

 - Ed Kyle

I think there is no need to pretend ignorant and repeat questions that have been discussed times before, right?

Supersynchronize is less efficient in most cases, and orbit also matters, I think few will doubt that Shuttle is more powerful than F9, even it can launch zero payload to GTO without an upper stage. Plus, may I ask is there any relationship between different launch sites and the power of rocket?

[ugordan]

So if this is true then it would seem we could get more out of falcon heavy by further strengthening the center core.

That's not the only consideration, though. Payloads have a design limit for axial loads and even if your strengthened vehicle can handle higher loads, if it makes the overall stack acceleration higher than that, it's not really useful for your typical payload. For Falcon payloads the max axial load factor must be kept under 6 G for “standard” payload mass (over 4,000 lb). Special payloads could of course be made to accomodate higher loads, but GEO satellites are what I'd call a "typical" payload.

[crandles57]

I thought I heard limiting stresses on center core for the first one.
This would make sense as nearly empty side boosters transmit more force to the center core.
So if this is true then it would seem we could get more out of falcon heavy by further strengthening the center core. Or maybe spacex is not pushing the center core structure and attachments to their design limits yet.

Why not assume it has been strengthened as much as they can without adding a lot of weight? Doubt a redesign is going to happen (all effort on BFR). May not want to go as far as design limits on as early a flight as 2nd. Getting attachments back to check them after challenging flight is good

If centre core is run throttled back for much of the time, was wondering if Falcon Heavy could take off with just 5? engines on the centre core rather than have weight of 9. Now seems possible that it is more likely that the stress through the attachments may be the/a more important limiting factor? Or maybe there is some other even more important limiting factor?

[envy887]

Terrific launch for SpaceX, and at a key moment with NSSL and NASA's SLS frustration underway. 

I have only one note about the news coverage.  Repeatedly, it is written that Falcon Heavy is "the world’s most powerful operational launcher", etc., which technically is true in terms of liftoff thrust, but FH-2 only put 6,465 kg into GEO-1500-ish m/s.   That's only 64% or so of what Ariane 5 ECA has boosted to an equivalent orbit.  All of that thrust is neat, but much of it is not being used for the actual payload mission.

 - Ed Kyle

Power isn't a good metric for measuring payload capacity. But FH can easily beat A5 ECA on either.

[Johnny6000]

A true marvel, what a time to be alive !!!!

Sent from my Pixel 3 XL using Tapatalk

[Llian Rhydderch]

Debates between different rocket engineers about which rocket can do more on this or that metric never really answer the question.

The MARKET answers the question.  Which rocket is being chosen by those entities that have to put skin in the game and purchase an orbital launch.

SpaceX is eating the market.  Look at the ten year graph here.

[edkyle99]

Terrific launch for SpaceX, and at a key moment with NSSL and NASA's SLS frustration underway. 

I have only one note about the news coverage.  Repeatedly, it is written that Falcon Heavy is "the world’s most powerful operational launcher", etc., which technically is true in terms of liftoff thrust, but FH-2 only put 6,465 kg into GEO-1500-ish m/s.   That's only 64% or so of what Ariane 5 ECA has boosted to an equivalent orbit.  All of that thrust is neat, but much of it is not being used for the actual payload mission.

 - Ed Kyle

Power isn't a good metric for measuring payload capacity. But FH can easily beat A5 ECA on either.

It could, in expendable mode, but SpaceX doesn't seem to be planning to use it that way.  I'm not sure it would cost less than an Ariane 5 if flown expendably.

 - Ed Kyle

[Vettedrmr]

If fuel was unlimited, you could slow them down to a certain speed before hitting atmosphere and all booster landings would be same stress/toastiness.

However fuel isn't unlimited. If a challenging mission, you want atmosphere to do as much of the work of slowing down the booster as possible without booster getting too hot in order to conserve the amount of fuel needed, at least on missions that are payload mass challenging and/or on GTO & faster missions. The more challenging the mission the more work is left to atmosphere and booster gets toastier.

Agreed.  BUT, I thought one of the things about this mission was the "light weight" impact of the mission, which implies (at least to me) that there would be a fairly good fuel supply.

But yeah, if the mission is at the upper limits of recoverability, then you've got to balance reentry decel burns vs enough fuel to land.

Have a good one,
Mike