Author Topic: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion Thread 1  (Read 581993 times)

Online russianhalo117

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #140 on: 11/02/2017 06:41 PM »
I remember Elon Musk saying that he's worried about a possible pad explosion, so if Falcon Heavy clears the tower, he's relieved for the time being because then the vehicle has to go through Max-Q, which could potentially rip everything apart if there's one or more defects.

And about the side core separation, well, there's no separation rockets, so we'll hope for the best.
AFAIK, Cold gas thrusters on the top of the side boosters will be fired at separation to impart separation and arcing away from the core boosters velocity vector.
« Last Edit: 11/02/2017 06:42 PM by russianhalo117 »

Online IanThePineapple

I remember Elon Musk saying that he's worried about a possible pad explosion, so if Falcon Heavy clears the tower, he's relieved for the time being because then the vehicle has to go through Max-Q, which could potentially rip everything apart if there's one or more defects.

And about the side core separation, well, there's no separation rockets, so we'll hope for the best.
AFAIK, Cold gas thrusters on the top of the side boosters will be fired at separation to impart separation and arcing away from the core boosters velocity vector.

And the boosters' center engines will fire for a little bit after separation for high control

Online russianhalo117

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #142 on: 11/02/2017 06:48 PM »
The side booster staging event is going to be the money event of this launch.  We haven't seen a staging event like that since shuttle.
Just how different is it from what happens on Delta 4 Heavy launches?

It's different than the Space Shuttle and Delta IV Heavy because the Falcon Heavy side cores are NOT equipped with separation rockets, or in KSP terms "sepratrons."

Cold-gas thrusters are too weak to help with the separation process.
not all Cold gas thrusters are weak. Sort of hot staging the boosters is what i have seen elsewhere.
« Last Edit: 11/02/2017 06:50 PM by russianhalo117 »

Offline Mike Jones

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #143 on: 11/02/2017 06:52 PM »
Any clue about the payload for this Falcon Heavy maiden flight ?

Online spacenut

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #144 on: 11/02/2017 06:53 PM »
I would love to see them launch a Dragon capsule around the moon and back on the first launch. 

Offline envy887

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #145 on: 11/02/2017 06:59 PM »
Any clue about the payload for this Falcon Heavy maiden flight ?

Nothing at all definitive.

Online russianhalo117

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #146 on: 11/02/2017 07:02 PM »
I would love to see them launch a Dragon capsule around the moon and back on the first launch. 
To much internal risk as Dragon v2 still hasn't flown to LEO yet and SpaceX's BEO communications network not yet ready worldwide to handle such a mission.

Offline Lar

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #147 on: 11/02/2017 07:04 PM »
Can grid fins help with separation? Or is the aerodynamic regime too severe, or does using them 'in reverse' just not work? (turning them 180 at speed might not be the best approach.
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Online spacenut

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #148 on: 11/02/2017 07:07 PM »
Since this is a demo, I was thinking about re-using a Dragon I capsule they use to supply ISS.  Just as a Demo, not a lot of money to spend. 

Online gongora

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #149 on: 11/02/2017 07:10 PM »
Payload speculation/wishes don't go here, use the FH Demo Payload Speculation thread.

Offline deruch

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #150 on: 11/02/2017 07:28 PM »
Can grid fins help with separation? Or is the aerodynamic regime too severe, or does using them 'in reverse' just not work? (turning them 180 at speed might not be the best approach.
Given the "floppiness" of gridfin deployments, I wouldn't expect them to work well with deploying against large forces in the opposite direction.  And the middle of a separation event isn't high on my list of times I'd like unpredictable force transients somewhat randomly applied to the nose of my vehicle.  But, I'm not at all sure that booster separation will be taking place low enough in the atmosphere for this to be an issue.  And, if it isn't low enough to be a factor nor will it be low enough to help/interfere with the separation either.
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Offline georgegassaway

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #151 on: 11/03/2017 03:57 AM »
Would not want to have the nose section of the outer boosters to do the main work of separation.  imagine if SpaceX used just explosive bolts and suddenly the three were flying free in parallel, and only forces on the noses pushed the boosters outward, nothing else. The rear of the boosters would pivot (pinch) inwards and hit the center core (due to pivoting about their CGs). 

So for one, they need some rear attachment system on the Octawebs that will either allow the outer boosters to pivot outwards, or for the rear attachments to actively push the rear of the boosters outwards during separation (but at less of an acceleration rate than the noses are pushed outwards, to produce an outwards yaw rotation rate).  While the forward attachments will actively push the noses outwards pneumatically.

Once separated with some outwards velocity vector, and rotating (yawing) outwards a few degrees, whatever small amount of aerodynamic forces  (thin air) should help to push them outwards even more, crude aerodynamic lift despite not having the grid fins deployed yet. With the center core accelerating away, the outer boosters will be left behind quickly, and those boosters will be moving apart from each other, so the RCS (if not already used in the separation process) can work to pivot the boosters around quickly enough to begin the Boostback maneuver.
« Last Edit: 11/03/2017 05:57 AM by georgegassaway »

Offline Comga

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #152 on: 11/03/2017 04:09 AM »
What would happen if the center engines or (engine trios) were left on but kept pointed counter to the axis of the center stage, up to some angular limit? 
Suppose the acceleration of the nearly empty boosters is close to that of the center core.
Given a "modest" push outward, the boosters would "fall" outward. 
There would be some reaction towards the center core at the base, as their CGs would be low, but not at the pivot.
However, this could be counteracted by pivoting the engine(s) to thrust slightly outward.   
When the angular limit was hit, the thrust would push the boosters out.
Perhaps as george suggested this could continue into the boostback maneuver.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Steven Pietrobon

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #153 on: 11/03/2017 07:38 AM »
The Russians solved the booster separation problem years ago with the R-7 (now Soyuz) without the need of solid separation motors. I believe the R-7 vents its LOX tank to help tip over the booster. Perhaps SpaceX is doing the same.
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Offline ugordan

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #154 on: 11/03/2017 08:15 AM »
I believe the R-7 vents its LOX tank to help tip over the booster. Perhaps SpaceX is doing the same.

R-7 strapons arent required to reignite seconds later for RTLS and I'm not sure venting the tank would be such a good idea.
2) F9 LOX vents are actually directed downwards, not sideways so they wouldn't do much.

Also, not that it matters that much, the placement of the vents vs core attachment would make the strapons separate a-la Titan IV SRMs and unlike Delta IV Heavy (sideways).

Offline woods170

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #155 on: 11/03/2017 08:28 AM »
I believe the R-7 vents its LOX tank to help tip over the booster. Perhaps SpaceX is doing the same.

R-7 strapons arent required to reignite seconds later for RTLS and I'm not sure venting the tank would be such a good idea.
2) F9 LOX vents are actually directed downwards, not sideways so they wouldn't do much.

Also, not that it matters that much, the placement of the vents vs core attachment would make the strapons separate a-la Titan IV SRMs and unlike Delta IV Heavy (sideways).

Has anyone here considered a solution to the separation event along the lines of Ariane 3 and Ariane 4?

Offline vanoord

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #156 on: 11/03/2017 08:31 AM »
Since this is a demo, I was thinking about re-using a Dragon I capsule they use to supply ISS.  Just as a Demo, not a lot of money to spend.

99.99% this flight will have a fairing - they need to fly the vehicle with three times (IIRC) to qualify it for government contracts.

What's inside the fairing is the question, but (i) it's not going to be a Dragon; and (ii) in that case it won't be coming back in one piece.

The words 'school' and 'bus' seem to have featured - but from my way of thinking, I doubt their structure is designed for the sort of G-loadings that orbital launch is going to put on them  (  ::) ) and it would be a lot easier just to use a mass simulator. Not to mention that if it's been Elon's idea, then he's busy trying to get the Tesla Model 3 into mass production, so humorous payloads are going to be much less of a priority.

My own thought was that if they were looking for a payload to carry inside a Dragon capsule, then some sort of commemorative metal discs (call them coins, medallions, whatever) which could be used as ballast, then recovered and  sold - I reckon there are plenty of people who would have been happy to pay for a commemorative coin that had been orbitally flown.

To be honest, if it's got a payload fairing on, a mass simulator inside and a modified S2 with heat tiles to see how long it can survive re-entry; and if the whole thing launches without failure, then it'll be a very good outcome.

Offline cuddihy

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #157 on: 11/03/2017 10:10 AM »

Has anyone here considered a solution to the separation event along the lines of Ariane 3 and Ariane 4?

What are you suggesting?

Offline woods170

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #158 on: 11/03/2017 11:20 AM »

Has anyone here considered a solution to the separation event along the lines of Ariane 3 and Ariane 4?

What are you suggesting?
Sorry. I keep forgetting that not everyone here is familiar with the earlier versions of the Ariane launch system.

What I am referring to is spring-assisted separation event.

Offline old_sellsword

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #159 on: 11/03/2017 12:04 PM »
So for one, they need some rear attachment system on the Octawebs that will either allow the outer boosters to pivot outwards, or for the rear attachments to actively push the rear of the boosters outwards during separation (but at less of an acceleration rate than the noses are pushed outwards, to produce an outwards yaw rotation rate).  While the forward attachments will actively push the noses outwards pneumatically.

Both the nosecones and the octawebs have pneumatic pusher mechanisms, and the octawebs also have a beefy connection point at the hold-down lugs. Whether or not that pivots before full separation is to be seen though.

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