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

[Lee Jay]

Elon Musk is a human Crazy Eddie.

Not to put down recent acheivements, but Bono and others had ideas for making rockets reuseable back in the 60s. Even the first concepts for Collier's magazine in the 50s had a booster that would be recovered for later use.

Space X has acheived great successes and have revolutionised spaceflight. It's sad that nobody has acted on the possibilities  within the last *FIFTY YEARS*.

A few of us tried. 

Did you work on DC-X? A real shame that couldn't have been followed through. I suppose the demise of MacDac had something to do with it.

Look up "Roton" as well.

[ugordan]

Was the briefcase thing new for this webcast?

Yes, like I said above.

[the_other_Doug]

You're much better off listening to the countdown net audio loop of the original (unedited) webcast than trying to hear anything through all the cheering.

How do you go about listening to that?

Go to

and click on that briefcase-looking thing in the lower right with arrows on it and it'll allow you to switch feeds.

Be aware that this option is available on YouTube through a web browser.  This option isn't available, for example, on many of the YouTube apps available on phones, apps, media devices, etc.

[IntoTheVoid]

My guess on center stage failure:

If musk is right that the outer 2 engines failed ignition and the center was good then how about the heating caused the tea/teb to boil in the lines. Maybe because it is a new design they didn't route the lines the same way as the sides.

I believe he posited that they ran out of TEA/TEB. And I suspect that even for a 3 engine landing burn, they would light the center 1st as that appears to be how they always do it. As to why they ran out of TEA/TEB, I saw other speculation that perhaps it had to do with the higher starting velocity of the earlier burns. Even the GTO launches that are close in MECO velocity don't normally do a boostback, which obviously reduces the TEA/TEB consumption.

[stcks]

Does anyone have a list/table of first stage MECO altitude/velocity data and comparison with recovery outcome for all v1.2/Heavy missions? I have seen such a table updated yesterday (in French IIRC) that indicates that the central core for this launch was the stage with the highest velocity at MECO that have been attempted to be recovered so far - at around 2.65 km/s, comparable with those expended stages for heavy GTO F9 missions. Unfortunately I can't seem to find it back, so if you know where I can find this please post here!

Musk said the hottest recovered booster was BulgariaSat, which staged at ~8500 kph. FH staged over 1000 kph faster.

I maintain one for GTO missions over on the reddit wiki. I'll think about also including the LEO missions but no promises. Check out the following: https://www.reddit.com/r/spacex/wiki/launches/gto_performance

Additionally, while BulgariaSat was the fastest MECO for a recovered stage, Inmarsat 5-F4 was the fastest for any core at 2720.3 m/s, which is a decent amount faster than even this FH mission.  This FH mission staged at nearly the same MECO as Intelsat 35e, which of course was an enormous GEO comsat.

[ugordan]

Posting this for the sake of the commentary.

Dude.

[3Davideo]

Am I correct this is the first working space suit sent to Earth escape - and for that matter the first sent beyond LEO since Apollo? 

[OxCartMark]

This FH mission staged at nearly the same MECO as Intelsat 35e, which of course was an enormous GEO comsat.

  What am I missing here, a single stick pushed a very large payload to the essentially the same speed as three were capable of doing with a light load (light even for a single stick)??  I know its expendable vs. recoverable but recoverability doesn't make that huge of a difference does it?  What am I missing?

------------------

What about the timing of the earth departure burn last night, it was generally projected for Quito but in actuality they did it ~10 minutes earlier near (more or less) L.A.  One factor was that they weren't aiming for a precision target and once the decision to burn to completion was made were even more imprecise in what they ended up with.  But I speculate (or maybe its obvious to all already) that they did it as a visual self indulgence for the employees of SpaceX in L.A..  Thoughts?

edit: would it be possible to plan such a thing on the fly once the launch didn't go off at the beginning of the window?

[envy887]

This FH mission staged at nearly the same MECO as Intelsat 35e, which of course was an enormous GEO comsat.

  What am I missing here, a single stick pushed a very large payload to the essentially the same speed as three were capable of doing with a light load (light even for a single stick)??  I know its expendable vs. recoverable but recoverability doesn't make that huge of a difference does it?  What am I missing?

------------------

What about the timing of the earth departure burn last night, it was generally projected for Quito but in actuality they did it ~10 minutes earlier near (more or less) L.A.  One factor was that they weren't aiming for a precision target and once the decision to burn to completion was made were even more imprecise in what they ended up with.  But I speculate (or maybe its obvious to all already) that they did it as a visual self indulgence for the employees of SpaceX in L.A..  Thoughts?

edit: would it be possible to plan such a thing on the fly once the launch didn't go off at the beginning of the window?

I wouldn't read too much into the performance of this mission. They did a slow LOX load and ran a very conservative throttle profile, and did a major boostback with the center core.

This was just to see if they could get it to work, now they will see how much margin was left over and how much they can safely push the envelope.

[stcks]

This FH mission staged at nearly the same MECO as Intelsat 35e, which of course was an enormous GEO comsat.

  What am I missing here, a single stick pushed a very large payload to the essentially the same speed as three were capable of doing with a light load (light even for a single stick)??  I know its expendable vs. recoverable but recoverability doesn't make that huge of a difference does it?  What am I missing?

You're not missing anything. FH recoverable is not nearly as powerful as FH expendable. Thats just how it is. However, the center core enjoyed a much more docile re-entry than a typical GTO mission would thanks to that long boostback burn. What this mission showed is that the heaviest GTO comsats on the market today quite easily within range of FH with full reflyable-recovery. More than that, such as heavy BEO with recovery, etc, remains to be proven.

[LouScheffer]

Additionally, while BulgariaSat was the fastest MECO for a recovered stage, Inmarsat 5-F4 was the fastest for any core at 2720.3 m/s, which is a decent amount faster than even this FH mission.  This FH mission staged at nearly the same MECO as Intelsat 35e, which of course was an enormous GEO comsat.

The MECO they picked for this mission (I suspect) was another of their test objectives - to show that FH, fully recoverable, can fly any mission the F9 can fly expendable (such as Inmarsat and Intelsat), even with a partial boostback and the ASDS relatively close to shore. 

How much better can SpaceX do?  By eliminating the center core boostback and positioning the ASDS farther out, they can do better yet.   Boostback on this mission appeared to last 48 seconds, with 3 engines.  If you skipped it, that would give 16 more seconds of booster power.   Assuming you can use 12 seconds of this to go faster at MECO (and the other 4 seconds worth to slow down the booster, which is about 1/4 the mass after the second stage separates), and the stage is accelerating about 5G at cutoff, that's 600 m/s more at MECO, while still recovering all boosters.  So I suspect they can stage in the 3300 m/s range, with the droneship far out at sea, and recover all boosters with no hotter entry than today.

[groundbound]

Posting this for the sake of the commentary.

Dude.

The commentators appear to be fueled by different hydrocarbons than RP1.

[stcks]

How much better can SpaceX do?  By eliminating the center core boostback and positioning the ASDS farther out, they can do better yet.   Boostback on this mission appeared to last 48 seconds, with 3 engines.  If you skipped it, that would give 16 more seconds of booster power.   Assuming you can use 12 seconds of this to go faster at MECO (and the other 4 seconds worth to slow down the booster, which is about 1/4 the mass after the second stage separates), and the stage is accelerating about 5G at cutoff, that's 600 m/s more at MECO, while still recovering all boosters.  So I suspect they can stage in the 3300 m/s range, with the droneship far out at sea, and recover all boosters with no hotter entry than today.

Do you think an additional 4 seconds at entry-burn is enough to allow a center core coming in that hot to survive? Thats the real question. What does Block 5 have up its sleeve for Falcon Heavy?

Edit: I guess that would actually be 12 seconds or so on 3 engines... would be super nice to see some math here

[cebri]

Miles O'Brien report 

[envy887]

How much better can SpaceX do?  By eliminating the center core boostback and positioning the ASDS farther out, they can do better yet.   Boostback on this mission appeared to last 48 seconds, with 3 engines.  If you skipped it, that would give 16 more seconds of booster power.   Assuming you can use 12 seconds of this to go faster at MECO (and the other 4 seconds worth to slow down the booster, which is about 1/4 the mass after the second stage separates), and the stage is accelerating about 5G at cutoff, that's 600 m/s more at MECO, while still recovering all boosters.  So I suspect they can stage in the 3300 m/s range, with the droneship far out at sea, and recover all boosters with no hotter entry than today.

Do you think an additional 4 seconds at entry-burn is enough to allow a center core coming in that hot to survive? Thats the real question. What does Block 5 have up its sleeve for Falcon Heavy?

Edit: I guess that would actually be 12 seconds or so on 3 engines... would be super nice to see some math here

BOTE

If entry starts at 3.5 km/s (about Mach 12) the additional burn of 12 seconds at 6.5 gees would slow it by an extra 760 m/s or to about 78% of the initial speed. If peat heating scales with speed cubed that's .78^3 or 48% of the initial entry heating.

The faster you are going, the more a little bit of braking helps.

[LouScheffer]

How much better can SpaceX do?  By eliminating the center core boostback and positioning the ASDS farther out, they can do better yet.   Boostback on this mission appeared to last 48 seconds, with 3 engines.  If you skipped it, that would give 16 more seconds of booster power.   Assuming you can use 12 seconds of this to go faster at MECO (and the other 4 seconds worth to slow down the booster, which is about 1/4 the mass after the second stage separates), and the stage is accelerating about 5G at cutoff, that's 600 m/s more at MECO, while still recovering all boosters.  So I suspect they can stage in the 3300 m/s range, with the droneship far out at sea, and recover all boosters with no hotter entry than today.

Do you think an additional 4 seconds at entry-burn is enough to allow a center core coming in that hot to survive? Thats the real question. What does Block 5 have up its sleeve for Falcon Heavy?

Edit: I guess that would actually be 12 seconds or so on 3 engines... would be super nice to see some math here

Compared to this mission, they spend 12 seconds going faster with 9 engines, then 12 seconds slowing down with 3.  But when speeding up, they are pushing the 125 tonne second stage as well as the core.  When slowing down, it's only the core.  So if the core is less than 62 tonnes, it will slow down more than it sped up, and have a gentler entry than today.   The core masses about 27t empty, folks think.  Each Merlin eats about 270 kg/sec.  So the landing burn takes 30 sec * 1 engine * 270 kg = 8100 kg of fuel (3 engine landing is a little better).  Re-entry burn takes about 20 sec with 3 engines, for about 16.200 kg.  So the normal entry burn starts with about 27 + 8 + 16 = 51t.  Well under the 62 t requirement, so the 12 seconds of extra re-entry burn should be more than sufficient.

[AC in NC]

What am I missing here, a single stick pushed a very large payload to the essentially the same speed as three were capable of doing with a light load (light even for a single stick)??  I know its expendable vs. recoverable but recoverability doesn't make that huge of a difference does it?  What am I missing?

Don't forget it was overall running at 92% of ultimate thrust.  And it had a huge 6.5-7 gap from ignition to release.

Yes recoverability is huge.  See the FH exp vs. recov performance.

[cebri]

See you later Starman 



https://twitter.com/elonmusk/status/961359174230773765

[OxCartMark]

Super bowl on Sunday, FH first launch on Tuesday. FH launch cost to commercial customers $90M.  Super Bowl ads sold for $10M / minute (plus production of the commercial).  Total of all ad revenue for the entire Super Bowl broadcast: $400+M. (that would imply 40+ minutes of ads, seem correct??).  So what we saw yesterday was Tesla's (and SpaceX's) Super Bowl ads combined with a test flight that was going to happen anyway.  Just take a test flight and add a few cameras and a car and a well dressed scarecrow.  There are a lot of ways to look at this and account for the expenses but one way would be to say that the cost of the test flight was already accounted for outside of the advertising budget and all the advertising budget had to pay for was the car (donated actually, I presume), the video equipment and various custom mounts, the payload adaptor, development, testing, ground receive network, what's that, hmm, less than $5M, 30 seconds of TV ad time I'd guess.  Front page of most newspapers I hear.  Will be in peoples' minds for a long time, longer than the Tide detergent commercials (its been 3 days now, do you remember them?).  Tesla stock up $11 today while the Dow is down.  Tesla's market capitalization increased by 1-3/4 billion dollars today though who knows how much of it if any is attributable to seeing a Tesla car going off into the distance while heading away from the horizon.

[Rocket Science]

Posting this for the sake of the commentary.

Dude.

The commentators appear to be fueled by different hydrocarbons than RP1.

They also had an awesome spot picked out to watch. Can anyone ID the location?