SpaceX Falcon Heavy Demo - Discussion and Speculation

[Jim]

Most likely, but down-throttling is more of an optimization than neccessary.

It is necessary because that is what the whole 3 identical core concept is based on.  It is a waste to use 3 cores and burn them equally to boost the same upper stage that is used on a single core.  If using 3 cores and burn them equally, then a larger second stage is needed.  If not, when one uses 3 identical core and same upper stage, then the middle core is throttle down to save propellant, turning it into a second stage.  This is much like the Titan III/IV.

With cross-feed implemented, down-throttling is not neccessary.

Cross feed is not happening

[Roy_H]

..., but down-throttling is more of an optimization than neccessary.

Optimization is the difference between a rocket that makes it to orbit and one that does not. Most of what makes one rocket better than another is because of superior optimization (as opposed to different fuels or type of engine).

[llanitedave]

my $0.02  can throttle the two outside cores higher and keep center core more fueled at staging..  a "triangle" makes that harder..
jb

Most likely, but down-throttling is more of an optimization than neccessary. With cross-feed implemented, down-throttling is not neccessary.

You can't have it both ways.  Crossfeeding would imbalance a triangle arrangement, if you want crossfeed then it necessarily has to be a side-by-side stack.  Same is true with downthrottling one core.  In fact, having a triangle arrangement with the payload one one leg is inherently unstable, and balancing the fuel load and thrust would be far more complicated than a center core and two sides, whether you crossfeed or not.


And crossfeed isn't happening anyway, so no need to fret about it.

[Space Ghost 1962]

Crossfeeding is an enhancement, to keep even more propellant in the core by the time the side boosters stage.

In terms of vehicle strategy, you can:
 a) use the three boosters to loft a larger US for either lower staging/more second stage delta V (C3, payload, in space propulsion, side boosters unchanged)
 b) use the side boosters to loft stack to allow core as "low" second stage and US as third (ditto but US also unchanged)
 c) cross feed to core preserving "high" second stage core US third (most but all boosters changed from F9)

Option c) wrecks reuse economics as Block 5 would have three instead of two variants. You already have excess payload and desire most maximal reuse/commonality to get rapid payoff on reuse investment. Also does not aid in advancing to a fully reusable vehicle, which would be you're best option for a F9/FH family program completion, which might allow a future vehicle program to build upon its successes, designed from the ground up completely differently for that scale.

(Even Dragon doesn't fit the SX aspirations beyond F9/ISS and FH/lunar much. Too much scope creep.)

[wannamoonbase]

Crossfeed simply isn't required to perform they missions they have on the books.

I still day dream about it though, the capability increase would be exciting. 

The side boosters burnout time and velocity would be lower and easy for recovery. 

The core on the other hand would be so far down range for recovery.

A shame we'll never see this, but that is a minor concern, I just want a simple FH to fly at this point.

Edit: Any guesses on how much longer the non-crossfeed center core will burn compared to the sides?  Is 30 seconds too long?

[oldAtlas_Eguy]

Crossfeed simply isn't required to perform they missions they have on the books.

I still day dream about it though, the capability increase would be exciting. 

The side boosters burnout time and velocity would be lower and easy for recovery. 

The core on the other hand would be so far down range for recovery.

A shame we'll never see this, but that is a minor concern, I just want a simple FH to fly at this point.

Edit: Any guesses on how much longer the non-crossfeed center core will burn compared to the sides?  Is 30 seconds too long?

Yes, a 20-30% payload increase would be 76 to 83mt LEO. But costs would make the vehicle only a choice for a SLS replacement.

[Rhyshaelkan]

Will be down at Disney/Universal Studios Nov 2nd-Nov 12th. Did not think of the possibility of seeing this in person. Would be my first and most epic launch.

[cscott]

I'd expect a healthy number of scrubs before it gets off the pad. Lots of new procedures to debug.  Be cautious scheduling travel around this launch.

[georgegassaway]

If I were to plan to see a FH launch, I'd wait for one where they have a light enough payload to allow for a center core RTLS landing. So, to see one launch, and three landings.  But that will be several 6 months down the road, and require a 3rd landing pad to be built first. My other choice would be for the Lunar Joyride launch, if the side boosters will RTLS.

[Zed_Noir]

If I were to plan to see a FH launch, I'd wait for one where they have a light enough payload to allow for a center core RTLS landing. So, to see one launch, and three landings.  But that will be several 6 months down the road, and require a 3rd landing pad to be built first. My other choice would be for the Lunar Joyride launch, if the side boosters will RTLS.

No need for a third pad. Just park the ASDS OCISLY off shore from LZ-1 at Canaveral AFS.

[speedevil]

Crossfeed simply isn't required to perform they missions they have on the books.

I still day dream about it though, the capability increase would be exciting. 

In principle, once FH has flown a few times, they can start carefully looking at sensor data, and throttling down the engines on the centre core more aggressively.
This doesn't get you quite to crossfeed numbers, but may provide an interesting bonus as time goes on.

[tdperk]

I'd expect a healthy number of scrubs before it gets off the pad. Lots of new procedures to debug.  Be cautious scheduling travel around this launch.

I'm more interested in the 2nd launch.

[cscott]

I'd expect a healthy number of scrubs before it gets off the pad. Lots of new procedures to debug.  Be cautious scheduling travel around this launch.

I'm more interested in the 2nd launch.

I've got tickets to observe the lightsail mission. That looks like it will be the third launch at this point.

[meekGee]

If I were to plan to see a FH launch, I'd wait for one where they have a light enough payload to allow for a center core RTLS landing. So, to see one launch, and three landings.  But that will be several 6 months down the road, and require a 3rd landing pad to be built first. My other choice would be for the Lunar Joyride launch, if the side boosters will RTLS.

The innovative side, seductive it is.

Greedy and insatiated, have we become.

[Wolfram66]

If I were to plan to see a FH launch, I'd wait for one where they have a light enough payload to allow for a center core RTLS landing. So, to see one launch, and three landings.  But that will be several 6 months down the road, and require a 3rd landing pad to be built first. My other choice would be for the Lunar Joyride launch, if the side boosters will RTLS.

The innovative side, seductive it is.

Greedy and insatiated, have we become.

Thanks Yoda 🤣

[wannamoonbase]

If I were to plan to see a FH launch, I'd wait for one where they have a light enough payload to allow for a center core RTLS landing. So, to see one launch, and three landings.  But that will be several 6 months down the road, and require a 3rd landing pad to be built first. My other choice would be for the Lunar Joyride launch, if the side boosters will RTLS.

No need for a third pad. Just park the ASDS OCISLY off shore from LZ-1 at Canaveral AFS.

The absence of requesting a third pad hinted to me that they don't see 3 cores RTLS anytime soon.

[AncientU]

If I were to plan to see a FH launch, I'd wait for one where they have a light enough payload to allow for a center core RTLS landing. So, to see one launch, and three landings.  But that will be several 6 months down the road, and require a 3rd landing pad to be built first. My other choice would be for the Lunar Joyride launch, if the side boosters will RTLS.

No need for a third pad. Just park the ASDS OCISLY off shore from LZ-1 at Canaveral AFS.

The absence of requesting a third pad hinted to me that they don't see 3 cores RTLS anytime soon.

Probably means next up is two RTLS cores... when three are expected, the third pad will be built.  Takes a couple months.

[oldAtlas_Eguy]

If I were to plan to see a FH launch, I'd wait for one where they have a light enough payload to allow for a center core RTLS landing. So, to see one launch, and three landings.  But that will be several 6 months down the road, and require a 3rd landing pad to be built first. My other choice would be for the Lunar Joyride launch, if the side boosters will RTLS.

No need for a third pad. Just park the ASDS OCISLY off shore from LZ-1 at Canaveral AFS.

The absence of requesting a third pad hinted to me that they don't see 3 cores RTLS anytime soon.

Probably means next up is two RTLS cores... when three are expected, the third pad will be built.  Takes a couple months.

A year or two for the paperwork and few months to construct.

[IanThePineapple]

If I were to plan to see a FH launch, I'd wait for one where they have a light enough payload to allow for a center core RTLS landing. So, to see one launch, and three landings.  But that will be several 6 months down the road, and require a 3rd landing pad to be built first. My other choice would be for the Lunar Joyride launch, if the side boosters will RTLS.

No need for a third pad. Just park the ASDS OCISLY off shore from LZ-1 at Canaveral AFS.

The absence of requesting a third pad hinted to me that they don't see 3 cores RTLS anytime soon.

Probably means next up is two RTLS cores... when three are expected, the third pad will be built.  Takes a couple months.

A year or two for the paperwork and few months to construct.

They have the paperwork for northern and southern pads, and the northern one is pretty much finished.

[Steve D]

They dont expect any circumstance where the center core will ever be RTLS. Too far downrange to come back.