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

[abaddon]

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.

If only SpaceX could have thrown away all three boosters and the payload fairings like so much used kleenex to prove that they can put more mass into space than anyone else.

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.

It must be so difficult for SpaceX to have to choose between vastly cheaper or vastly more capable, and not get both in the same rocket.

[Brovane]

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.

FH, about ~20,000 kg to GTO flying full expendable. 

[Star One]

I am assuming FH launching Europa Clipper would be a fully expendable launch being as to achieve its mission it would need a STAR upper stage as well?

[edkyle99]

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.

A good point.  Fair to note that SpaceX has mostly gained market from Proton and the late Sea Launch, whose losses are as much for political as for economic reasons.  Even Atlas has possibly been limited somewhat by the same geopolitical situation.  We'll have to see how things develop over a few more years.  Clearly SpaceX is going to remain a key player.

 - Ed Kyle

[ZachF]

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

Falcon Heavy with 3 core recovery is probably SpaceX's highest margin product.

They got 2/3rds of the performance of an A5 ECA while only expending one ~$10m upper stage.. A5 has to expend probably $150 million of equipment to match this, about an order of magnitude difference per kg of payload to GTO-1500. Also wouldn't be surprised if you backed out all the subsidies if the margin on an A5 was actually negative.

[su27k]

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.

This is a feature, not a bug. SpaceX's one-size-fits-all/dial-a-reuse strategy means one vehicle can cover a large range of payload capabilities, from your run-of-the-mill 6t GTO to 15t to TLI, all can be done by this one model, with varying degree of recovery/reuse options and different prices. This provides more flexibility than one-trick pony such as Ariane 5 ECA, but this also means you won't see FH's full power be used often, especially since FH is not built by government for a specific program thus will need time to find missions that can use its full capability. Really I don't see how this is different from the fact that the most powerful version of Atlas V flies much less often than less powerful configurations such as 401, except in FH's case the hardware difference between configurations is much smaller.

[NGCHunter]

Full tracking of side cores back to the landing and sonic booms, plus alternate landing view and tracking video.

Close Up Footage of Falcon Heavy Arabsat-6A!


Astronomy Live
Published on Apr 11, 2019

High magnification tracking footage of the launch and booster landing of the first block 5 Falcon Heavy from SpaceX! 

Tracked with an 8" LX200 Classic telescope using my custom UFOTraker software and a Canon T5i.  Special thanks to Reds Rhetoric for his static camera footage.

https://www.youtube.com/watch?v=cEZZkEXAD6Q?t=001

Beat me to it!  Thanks for posting my video.  What a fantastic launch that was, the weather was perfect for tracking yesterday.  The massive parade of boats from that vantage point forced me to stop down the tracking camera quite a bit though so that the program wouldn't confuse bright white boats with the bright white rocket plume.  This eventually caused me to have to shut off the auto tracking and take over manual control a little sooner than I anticipated.  On the whole though, it turned out great.

[rsdavis9]

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.

I was not thinking the overall g load would be higher but rather as experience of load limits of the attachments and core progresses that they can throttle back the center core more during 3 booster flight.

What is the merlin throttle limit? 30%?

So as spacex flies the heavy more we may see more performance unlocked?

[RedLineTrain]

All of that thrust is neat, but much of it is not being used for the actual payload mission.

Rather, it was used for the actual payload mission.  Margin of safety.

[49er]

At several points in the webcast the center core re-entry is described as "toasty".  Looking at the re-entry burn times, it appears that the re-entry burn for the side boosters is about 13 seconds while the center booster runs more than 26 seconds before the video cuts away (presumably to scrub off the excess speed of the downrange and higher altitude velocities).  So, if the booster is entering the upper atmosphere at about the same speed as the RTLS boosters, what makes it qualify as toasty?

[gongora]

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

Their prices are probably in the same ballpark when FH is flown expendable, and SpaceX is willing to fly expendable if the mission requires it.

[gongora]

1 44186U 19021A   19102.12070794 -.00000777  00000-0  00000+0 0  9990
2 44186  22.9554  12.6818 8700664 179.4894  42.9638  0.74112663    03

1 44187U 19021B   19102.12491049 -.00001400  00000-0  00000+0 0  9995
2 44187  22.9281  12.7290 8699691 179.2985  44.4599  0.74745982    01

Second stage is also cataloged now in the same orbit.

[Lar]

Drift warning... FH vs Atlas vs Ariane might not be quite as on topic as direct discussion of this particular mission would be....

[ugordan]

Beat me to it!  Thanks for posting my video.  What a fantastic launch that was, the weather was perfect for tracking yesterday.  The massive parade of boats from that vantage point forced me to stop down the tracking camera quite a bit though so that the program wouldn't confuse bright white boats with the bright white rocket plume.  This eventually caused me to have to shut off the auto tracking and take over manual control a little sooner than I anticipated.  On the whole though, it turned out great.

Allow me to thank you for the great footage you have provided to us for this launch as well as in the past. Your tracking setup is one of the best I've seen when it comes to "amateur" footage of rocket launches and your maiden FH launch footage is, to this day, one of my favorites.

You can see things in your footage that's difficult or impossible to see elsewhere. For example, adding on to my previous post here you can see that in this launch there is also a noticeable "disturbance" in the engine plume 3 seconds before BECO. Evidence of additional side core engines shutting down to limit loads?

Also, this view nicely shows that they're still using the 1-3-1 landing burn for the side boosters (if that wasn't already apparent by their rapid deceleration). I wonder why that is different from the single-stick landings at LZ-1? I thought they deemed the timing/throttle response margins being just too tight for comfort, at least they were for their ASDS landings in the past. Yet all of the FH boosters have employed it so far.

[ThereIWas3]

What came to mind as I watched the unfolding of the perfectly choreographed launch and landing sequence of this mission is that NASA has never done anything so complicated as this in a single launch, and they have no plans to.  Even the shuttle.  My immediate second thought was that NASA should get out of the launch vehicle business and leave it to people who are advancing the state of the art.

[Alexphysics]

At several points in the webcast the center core re-entry is described as "toasty".  Looking at the re-entry burn times, it appears that the re-entry burn for the side boosters is about 13 seconds while the center booster runs more than 26 seconds before the video cuts away (presumably to scrub off the excess speed of the downrange and higher altitude velocities).  So, if the booster is entering the upper atmosphere at about the same speed as the RTLS boosters, what makes it qualify as toasty?

The center core went at more than 10000kph e goin the return back to Earth, the side boosters were going half that speed when they were returning.

[lrk]

If the reason they are shutting down engines is to limit G-loading, wouldn't it make more sense to shut down engines on the center core than on the boosters?  This would allow them to burn more propellant on the side boosters than the center core, and would slightly improve payload.  3 of the center core engines are restartable, any engines that were shut down could be re-lit after staging. 

[Freddedonna]

If the reason they are shutting down engines is to limit G-loading, wouldn't it make more sense to shut down engines on the center core than on the boosters?  This would allow them to burn more propellant on the side boosters than the center core, and would slightly improve payload.  3 of the center core engines are restartable, any engines that were shut down could be re-lit after staging.

They can only relight the engines as long as they still have TEA-TEB in the tanks. The center core on the first FH launch failed to land because it ran out of it during the landing burn startup so I guess the margins are already pretty tight.

[rsdavis9]

If the reason they are shutting down engines is to limit G-loading, wouldn't it make more sense to shut down engines on the center core than on the boosters?  This would allow them to burn more propellant on the side boosters than the center core, and would slightly improve payload.  3 of the center core engines are restartable, any engines that were shut down could be re-lit after staging.

Possible stress limits on sides to center.
Attachments between
Structure of center core

[ugordan]

If the reason they are shutting down engines is to limit G-loading

Well, the big question right now is: is that really the case or is it simply a case of the individual octawebs and core attachments having an upper limit on force/torque exerted onto them.

wouldn't it make more sense to shut down engines on the center core than on the boosters?  This would allow them to burn more propellant on the side boosters than the center core, and would slightly improve payload.  3 of the center core engines are restartable, any engines that were shut down could be re-lit after staging. 

In an ideal world, yes. Crossfeed would be even better. But, alas, we live in the real world where engineering tradeoffs have to be made. Also, if there are really two separate load-limiting shutdown events on an FH block 5, that's *at least* 4 engines shut down in total, and only 3 are restartable on a core. Like I pointed out earlier, relying on relight of 3 engines adds an element of risk, because that's still the primary portion of the mission, the ascent phase. Booster recovery is just gravy.