Author Topic: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion  (Read 395410 times)

Online Lar

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #480 on: 12/23/2017 01:11 AM »
An ejectable/jettisonable nose cone is another part that has to be replaced each time. More expensive grid fins were likely a clearly better trade.
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Offline zhangmdev

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #481 on: 12/23/2017 01:25 AM »
Will there be camera on the side booster? Consider where the nose cone begins, it is hard for a downward facing camera to observe those gird fins.

Offline old_sellsword

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #482 on: 12/23/2017 01:55 AM »
An ejectable/jettisonable nose cone is another part that has to be replaced each time. More expensive grid fins were likely a clearly better trade.

Not to mention the fact you canít even jettison the nosecone because the grid fins are inside it...

Offline deruch

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #483 on: 12/23/2017 02:10 AM »
An ejectable/jettisonable nose cone is another part that has to be replaced each time. More expensive grid fins were likely a clearly better trade.

Not to mention the fact you canít even jettison the nosecone because the grid fins are inside it...

They could have made a 2-part assembly with a base/barrel section that housed the fins and control systems and a detachable upper/cone section, but clearly they chose a different route.  I'm sure lots of things played into that discussion beyond just reusability.  I was wondering on if it was an easy/clear choice or a more "could have gone either way" one.  Given they're already flying a reusable system, the improved grid fins seem like an easy choice. 
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Online tyrred

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #484 on: 12/23/2017 05:58 AM »
Will there be camera on the side booster? Consider where the nose cone begins, it is hard for a downward facing camera to observe those gird fins.
Looking closely at the inboard nosecones, are those camera pods on each, facing downwards towards the yellow linkage apparatus?  Perhaps I'm wrong, but it seems like a good place to situate a camera (to a layman).

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Offline macpacheco

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #486 on: 12/23/2017 08:28 AM »
The Titanium fins are installed on the side boosters to give them better glide ratio, reducing the duration of the boost back required that still gets the boosters to the LZ.
Since the center core lands on ASDS, they might handle the higher re-entry speed with a longer entry burn.
Just educated guesses, but it actually makes sense.
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Offline zhangmdev

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #487 on: 12/23/2017 10:05 AM »
Looking closely at the inboard nosecones, are those camera pods on each, facing downwards towards the yellow linkage apparatus?

The angle seems wrong. Grid fins and legs are likely outside field of view. But maybe they are more focused on observing how upper part of separation mechanism behaves. If they have side viewing cameras to document lower part of separation and keep recording all the way to touchdown, that would be awesome.


Offline clongton

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #488 on: 12/23/2017 12:35 PM »
Can someone explain why they didn't use the Tangent Ogive shape of the Ariane 5 booster?
« Last Edit: 12/23/2017 12:39 PM by clongton »
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Offline Rocket Science

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #489 on: 12/23/2017 12:42 PM »
Can someone explain why they didn't use the Tangent Ogive shape of the Ariane 5 booster?
My only theory is for boundary layer/flow separation symmetry and controlabilty for landing (as it then becomes a "boatail" during entry and approach) and maintain known flight control algorithms from Falcon 9 S1... However; I have no actual aero data to compare both during descent to back it up... I don't believe they are going to jettison the nose cone AFAIK....
« Last Edit: 12/23/2017 01:29 PM by Rocket Science »
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Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #490 on: 12/23/2017 12:50 PM »
Can someone explain why they didn't use the Tangent Ogive shape of the Ariane 5 booster?

Maybe it's from the experiences with Titan and Shuttle that have conic booster nose cones. With the nose cones on the Ariane V aerodynamic  forces are always going to be pushing the booster into the stage. Maybe the force produced with conic booster nose cones depends on the speed of the booster and can vary more. So harder to deal with.

At least that is what I think.




Offline Rocket Science

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #491 on: 12/23/2017 01:02 PM »
Can someone explain why they didn't use the Tangent Ogive shape of the Ariane 5 booster?

Maybe it's from the experiences with Titan and Shuttle that have conic booster nose cones. With the nose cones on the Ariane V aerodynamic  forces are always going to be pushing the booster into the stage. Maybe the force produced with conic booster nose cones depends on the speed of the booster and can vary more. So harder to deal with.

At least that is what I think.
With that in mind, it is interesting to note the current booster for SLS and the proposed "Dark Knight" configuration...
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Elon just tweeted this... 

https://twitter.com/elonmusk/status/944495421161742336

For those who don't do Twitter:

Quote
If you liked tonightís launch, you will really like Falcon Heavy next month: 3 rocket cores & 3X thrust. 2 cores return to base doing synchronized aerobatics. 3rd lands on droneship.
3:10 AM - 23 Dec 2017

That's a lot more confident-sounding than prior statements.
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Online Lar

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #493 on: 12/23/2017 01:23 PM »
Can someone explain why they didn't use the Tangent Ogive shape of the Ariane 5 booster?
Because Ariane 5 doesn't care about recovering the side boosters? They will have off kilter aerodynamics due to the strong asymmetry.

Also because reducing loads on the core may not be as important to this vehicle as it is to Ariane 5?
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Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #494 on: 12/23/2017 01:25 PM »
Because Ariane 5 doesn't care about recovering the side boosters?

Ariane 5 booster are recoverable, but it's not often done.
http://www.esa.int/esapub/bulletin/bullet85/gigo85.htm

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #495 on: 12/23/2017 01:30 PM »
Can someone explain why they didn't use the Tangent Ogive shape of the Ariane 5 booster?

Maybe it's from the experiences with Titan and Shuttle that have conic booster nose cones. With the nose cones on the Ariane V aerodynamic  forces are always going to be pushing the booster into the stage. Maybe the force produced with conic booster nose cones depends on the speed of the booster and can vary more. So harder to deal with.

At least that is what I think.
With that in mind, it is interesting to note the current booster for SLS and the proposed "Dark Knight" configuration...

Yea I forgot about that. But you're right. The Dark Knight nose cone is essentially the same as the Ariane 5 booster nosecone.
As for pushing the booster toward the core, the Poles had an easy solution to that on their Meteor-2K rocket - simply rotate the cone around 180 degrees, which might even improve the whole concern.
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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #496 on: 12/23/2017 01:34 PM »
Because Ariane 5 doesn't care about recovering the side boosters?


Ariane 5 boosters are recovered.
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Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #497 on: 12/23/2017 01:36 PM »
Also because reducing loads on the core may not be as important to this vehicle as it is to Ariane 5?

I was wondering this too. In the shuttle the boosters lift from their tops so there is a strong cross beam there able to withstand high loads. Falcon booster lift from the bottom, I don't know about Ariane 5 but looking at cutaways I think the boosters lift from the bottom as there is no crossbeam at the top of the booster as with the shuttle ET. I have even less idea about the Titan IV.

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #498 on: 12/23/2017 02:19 PM »
Because Ariane 5 doesn't care about recovering the side boosters?


Ariane 5 boosters are recovered.

But not reused?

Quote
The possibility of refurbishing and reusing the recovered boosters has, however, been rejected. It is currently considered a non-cost-effective option because of the specific design and reliability complications that this would incur. It is currently planned to recover four boosters per year.
(from http://www.esa.int/esapub/bulletin/bullet85/gigo85.htm cited above by nacnud.)

Why bother? Seriously. There might be some minor learnings but if you're not even going to TRY to reuse them, it's just a big boondoggle.  Some contracts must have been let and then found to be too expensive to cancel, or something.
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Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #499 on: 12/23/2017 02:31 PM »
Why bother? Seriously. There might be some minor learnings but if you're not even going to TRY to reuse them, it's just a big boondoggle.  Some contracts must have been let and then found to be too expensive to cancel, or something.

You could have said the same about reusing the shuttle boosters, IIRC the refurbishment cost was quite close to the cost of just building new each time. The reason for getting them back on occation is engineering data, validating the design.

While it's obvious now the way to get to reuse is liquid boosters as the refurbishment cost is lower having the Ariane booster solid kept the knowledge of how to build large solid alive in Europe. And solids are great when it comes to sitting inert in silos for extended periods of time...  :-\
« Last Edit: 12/23/2017 02:34 PM by nacnud »

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