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

[DaveH62]

Assuming the launch goes perfectly, and the 3 boosters are recovered...
Wouldn't it make any sense to refurb the 3 boosters and do a fully expendable launch ?
Be it a fully commercial launch or the first large StarLink satellite load ?
Or is it actually cheaper to retire them ?
I think recovery makes most sense if you fly them again...

It is my understanding the side boosters are pre-flown block 3, a reusable booster, but not as reusable as block 4. They will be saved for historical purposes. No block 3 rockets are being saved at this point, only block 4 and later this year only block 5. The main center stage 1 booster is a new block 4, but it too will likely be on display somewhere, as a set, assuming all goes well.

[CorvusCorax]

Question about trajectory

Musk said - if I remember right - the orbit should be stable millions of years.

General consensus seems to be that the trajectory will have an apogee as far out as mars but both out of plane and "behind" mars (since its launching too early for this years earth2mars launch window)

so there is no risk to ever hit mars or even have its orbit significantly disturbed by it.

but regardless if the perihelion remains at earth or is placed more sunwards than earth, the orbit would always intersect earths orbit  very closely at least in that one spot corresponding to the injection burn.

This can't be stable for millions of years. Sooner or later earth and the tesla will be in or near the same spots again as they were at time of injection burn, and then the spacecraft will either crash on earth, or will be slung out of its orbit by earths gravity assist to who knows where (if it gets slung all the way to Jupiters orbit, it might even at some point be slung out of the solar system if it doesn't crash into something)

To prevent that, the plane would have to be changed again so it intersects NEITHER mars nor earths orbit. But that would require either

1. A coast phase of days (if not weeks) to get far enough away from earth and then a plane change burn- AFAIK the falcon upper stage is not capable of doing that unless its more frankenstage than we ever thought

2. Use mars gravity to change the plane - but then the roadster would get close enough to mars to affect its orbit, which means it would likely eventually get close enough to mars again at some later time to change the orbit further


So how is this Roadster going to reach a stable million year orbit? Did they strip a solid rocket booster to the car?

Edit: Assuming Perihelion of the orbit is near earths orbit and Apohelion of the orbit is near Mars, that would lead a semi major axis of around 188 million kilometers and an orbital period of around 1.4 years. When originating at earth, such an orbit would likely get close enough to earth to be disturbed significantly after around 7 years (7 orbits of earth, 5 orbits of the roadster)

[quagmire]

I think recovery makes most sense if you fly them again...

Given this is the first launch of the Falcon Heavy, recovering all 3 boosters will be more important for data collecting post-flight then reusing them again. The second launch as well given the second launch of FH will be featuring Block 5 cores and probably built from the ground up as FH boosters vs conversions. Though would be curious on the time, cost, and effort it would take to convert a Block 5 Falcon 9 into a FH side booster and whether it could still be used as a single stick 1st stage given their goal of Block 5's being able to be reused at least 10 times. Given the lower launch cadence of the FH, they could still use the side boosters to increase F9 launch cadence.

[Lar]

Indy clips are surely party thread material.

Edit: All Harrison Ford stuff except the original post moved to the party thread. One post which was arguing with the mods about whether this was on topic or not? Sent to the aether.... That was fun, I like being mean and stuff. But don't make me do it again.

Party thread:  https://forum.nasaspaceflight.com/index.php?topic=42585.0

[cscott]

I think recovery makes most sense if you fly them again...

Given this is the first launch of the Falcon Heavy, recovering all 3 boosters will be more important for data collecting post-flight then reusing them again. The second launch as well given the second launch of FH will be featuring Block 5 cores and probably built from the ground up as FH boosters vs conversions. Though would be curious on the time, cost, and effort it would take to convert a Block 5 Falcon 9 into a FH side booster and whether it could still be used as a single stick 1st stage given their goal of Block 5's being able to be reused at least 10 times. Given the lower launch cadence of the FH, they could still use the side boosters to increase F9 launch cadence.

They'll cut some pieces out of various parts of the engines and tanks in order to do destructive analysis on metal fatigue, etc.  After you start punching holes in your rocket, it's best to retire it.

[hplan]

Anyone want to speculate on some of the missing values in this table?

- F9 recoverable  F9 expendable  FH fully recoverable  FH recoverable side cores  FH expendable  LEO ?? (a) 22.8 mT ?? (b) ?? (c) 63.8 mT GTO 5.5 mT 8.3 mT 8.0 mT ?? (d) 26.7 mT Cost $62m ?? (e) $90m ?? (f) ?? (g)

This assumes that the 5.5 mT and 8.0 mT price levels are for recoverable flights. (Otherwise why put in the weight limits?)

Hmmm, I never noticed before that an F9 expendable can lift more weight into GTO than an FH fully recoverable. Will an F9 expendable cost more than $90 million?

[TripD]

Assuming the launch goes perfectly, and the 3 boosters are recovered...
Wouldn't it make any sense to refurb the 3 boosters and do a fully expendable launch ?
Be it a fully commercial launch or the first large StarLink satellite load ?
Or is it actually cheaper to retire them ?
I think recovery makes most sense if you fly them again...

It is my understanding the side boosters are pre-flown block 3, a reusable booster, but not as reusable as block 4. They will be saved for historical purposes. No block 3 rockets are being saved at this point, only block 4 and later this year only block 5. The main center stage 1 booster is a new block 4, but it too will likely be on display somewhere, as a set, assuming all goes well.

The thought of all 3 boosters being reassembled for a display really makes me smile.

[sanman]

What are the odds on all 3 cores landing intact?

And what's the video coverage going to look like? 4-way splitscreen?

[guckyfan]

What are the odds on all 3 cores landing intact?

Assuming successful separation of the side cores, probably 98% or better. They really have the landing down to operational status even if they still tag them experimental. So it comes down to the odds of successful separation.

[CorvusCorax]

What are the odds on all 3 cores landing intact?

Assuming successful separation of the side cores, probably 98% or better. They really have the landing down to operational status even if they still tag them experimental. So it comes down to the odds of successful separation.

Well there's 3 hairy bits after booster separation to take into account:

1. Center core is going really fast, although they are probably going to take care of that with a lengthy "take it safe" reentry burn given the light payload

2. Center core has additional hardware (struts to side boosters) that affect aerodynamics a bit. Shouldn't be too drastic, but it hasn't ever flown in that configuration so definitely a first

3. Side  boosters have drastically different aerodynamics during atmospheric flights due to tailing nosecones versus interstage. SpaceX is worried about that enough to put giant Titanium gridfins on it, but that configuration, too has never flown before.

Considering these 3 things, even if separation and reentry of all 3 cores is successful, you can't really stop holding your breath until all 3 of them are safely on the ground.

[Johnnyhinbos]

Considering these 3 things, even if separation and reentry of all 3 cores is successful, you can't really stop holding your breath until all 3 of them are safely on the ground.

You’re gonna be holding your breath a long time then, cause that ASDS ain’t fast...! :-)

How far apart are the center core landing location and that of GovSat1? I should remember but my brain is currently in SpaceX overload...

[vanoord]

What are the odds on all 3 cores landing intact?

21/23* landing attempts have been successful for F9 v1.2 (ignoring Govsat-1 because I've no idea whether to consider it a landing attempt or not) - so that's 91% reliability.

In reality, the probability of landing any given core now should be higher due to experience - although that's tempered slightly by these not being Block 4 cores (which have a 5/5 success rate).

Say 95% for any given core - which nominally gives around 83% for getting all three back (under normal circumstances).

Then less a bit because this is experimental and there has to be a consideration about separation, control authority for the side cores and the effect of the hardware that links the cores together.

So perhaps 70% to 75%?



* they lost 2 v1.2 cores on landing - SES9 and Eutelsat 117W

[speedevil]

* they lost 2 v1.2 cores on landing - SES9 and Eutelsat 117W

Weren't both of those missions 'low fuel' ones?

[AncientU]

* they lost 2 v1.2 cores on landing - SES9 and Eutelsat 117W

Weren't both of those missions 'low fuel' ones?

That's a good point.  All RTLS landings, which almost by definition are low energy orbital launches, have been successful.  All low energy ASDS landings also have been successful, as have been nearly 100% of landings after finishing tweaking the software and hardware.

I'd say that the odds are very high -- maybe high 90s percent -- that all healthy cores will land successfully. 

Lets hope that's three.  Might be a lot lower.

[jpo234]

What are the odds on all 3 cores landing intact?

And what's the video coverage going to look like? 4-way splitscreen?

This being a webcast, it could make sense to have multiple parallel streams. one for each core and the second stage.

[meekGee]

What are the odds on all 3 cores landing intact?

21/23* landing attempts have been successful for F9 v1.2 (ignoring Govsat-1 because I've no idea whether to consider it a landing attempt or not) - so that's 91% reliability.

In reality, the probability of landing any given core now should be higher due to experience - although that's tempered slightly by these not being Block 4 cores (which have a 5/5 success rate).

Say 95% for any given core - which nominally gives around 83% for getting all three back (under normal circumstances).

Then less a bit because this is experimental and there has to be a consideration about separation, control authority for the side cores and the effect of the hardware that links the cores together.

So perhaps 70% to 75%?



* they lost 2 v1.2 cores on landing - SES9 and Eutelsat 117W

If the reliability is 91%, then the odds of 21 straight successes are only 15%...

A better explanation is that whatever was wrong with those first two launches got fixed.

When I got my first bike, I fell 10 times. I then got the hang of it and rode 20 times without falling. What are the odds I'll fall on my next attempt?

[octavo]

When I got my first bike, I fell 10 times. I then got the hang of it and rode 20 times without falling. What are the odds I'll fall on my next attempt?

100% if your older brother decides to jam a stick in the spokes as you take off. Painful first hand experience.

[meekGee]

When I got my first bike, I fell 10 times. I then got the hang of it and rode 20 times without falling. What are the odds I'll fall on my next attempt?

100% if your older brother decides to jam a stick in the spokes as you take off. Painful first hand experience.

And that's about the validity of the 21/23 argument.  If it fails now, it'll highly likely be because of something completely unrelated.

[jabe]

What are the odds on all 3 cores landing intact?

And what's the video coverage going to look like? 4-way splitscreen?

This being a webcast, it could make sense to have multiple parallel streams. one for each core and the second stage.

time to go buy a few more big flat screen monitors

[wannamoonbase]

When I got my first bike, I fell 10 times. I then got the hang of it and rode 20 times without falling. What are the odds I'll fall on my next attempt?

100% if your older brother decides to jam a stick in the spokes as you take off. Painful first hand experience.

LOL, yeah, we may have had the same older brother.

I think if they successfully separate the 2 side boosters then I think the mission, including recovery, will be fully successful.