Author Topic: Fairing reuse  (Read 562630 times)

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 28475
  • Minnesota
  • Liked: 8347
  • Likes Given: 5482
Re: Fairing reuse
« Reply #720 on: 03/28/2017 12:14 PM »
Two halves connected by a huge hinge? 😂
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Confusador

  • Full Member
  • **
  • Posts: 200
  • Liked: 41
  • Likes Given: 186
Re: Fairing reuse
« Reply #721 on: 03/28/2017 12:16 PM »
Two halves connected by a huge hinge? 😂

That was the idea, yes, from the very first page of this thread.  I think it's been done to death at this point.

Edit for clarity: I suspect Robotbeat remembers that, and is joking. But I don't want that to accidentally encourage anyone...
« Last Edit: 03/28/2017 12:18 PM by Confusador »

Offline rsdavis9

Re: Fairing reuse
« Reply #722 on: 03/28/2017 12:44 PM »
Zero evidence for this, but splitting the fairing into four would simplify things a fair bit.
What's your reasoning?

It seems to me it would just multiply the complexity: four avionics packages, four parafoils, four joints, four ASDSes, four helicopters, four airbags, etc.

In fact, some folks spent a lot of time upthread trying to figure out how to reattach the fairing halves after separation to create *one* flyback item.  That also adds a lot of complexity.

Seems like two halves is the sweet spot.  But I'm interested to hear why you think four is better.

Each piece is lighter and easier to "catch"?

I personally like barge with "fall bag" or basically large inflatable dome material.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Online Welsh Dragon

  • Full Member
  • **
  • Posts: 265
  • Liked: 261
  • Likes Given: 39
Re: Fairing reuse
« Reply #723 on: 03/28/2017 01:01 PM »
Zero evidence for this, but splitting the fairing into four would simplify things a fair bit.

The washering, flanging, and hardware for the joint adds a lot of weight.

Fair point. I can't t think of any LVs that use anything other than a two part clamshell.
Pretty sure some Titans used three part fairings.

Offline MP99

Re: Fairing reuse
« Reply #724 on: 03/28/2017 06:53 PM »
Two halves connected by a huge hinge? 😂

Make them flap, and you'd have an ornithopter!!  BFG.

Cheers, Martin


Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32426
  • Cape Canaveral Spaceport
  • Liked: 11164
  • Likes Given: 331
Re: Fairing reuse
« Reply #725 on: 03/28/2017 08:23 PM »
Zero evidence for this, but splitting the fairing into four would simplify things a fair bit.

The washering, flanging, and hardware for the joint adds a lot of weight.

Fair point. I can't t think of any LVs that use anything other than a two part clamshell.

Titan IV, Titan III, Delta II 10 metal, Skylab

Offline cscott

  • Senior Member
  • *****
  • Posts: 2949
  • Liked: 2054
  • Likes Given: 664
Re: Fairing reuse
« Reply #726 on: 03/28/2017 08:42 PM »
Didn't Apollo also have a four-part fairing around the LEM?

Online nacnud

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2334
  • Liked: 508
  • Likes Given: 226
Re: Fairing reuse
« Reply #727 on: 03/28/2017 08:46 PM »
Yep

Offline iamlucky13

  • Full Member
  • ****
  • Posts: 1660
  • Liked: 102
  • Likes Given: 93
Re: Fairing reuse
« Reply #728 on: 03/28/2017 11:28 PM »
Referring to fate seems to indicate something experimental.

Relaunch of a first stage is experimental.
It's almost like you and iamlucky13 have no idea of who Musk is. When Musk is given an opportunity to double down, he does. No way he's just a referring to reflying a stage.

When has he doubled down as you suggest?

Maybe I'm confused about who Musk is, but I'm fairly certain he's proud of his businesses and can't resist talking about them. When he's got something up his sleeve, he's generally dropped clear hints he's got something up his sleeve. He wants you paying attention for the punchline, not turning off the stream once the rocket touches down, so you miss the fairing landing.

Two make two more specific comments: using a fancy peace of ground support equipment to assist with recovery after the hard part is over is not fateful.

Successfully recovering a fairing is arguably fateful, but not nearly to the same degree as proving he really can refly rocket stages. Reflying a rocket stage is significant enough there's no reason to ascribe comments about fate to anything else unless Musk acts like Musk usually does and gives you a clear reason.

I have other reasons for expecting they will probably not be recovering a fairing this launch, but I'm not able to discuss them at this time.

Offline cscott

  • Senior Member
  • *****
  • Posts: 2949
  • Liked: 2054
  • Likes Given: 664
Re: Fairing reuse
« Reply #729 on: 03/29/2017 01:12 AM »
This will be a very hot landing, but if it comes back, SES gets "bits" for their boardroom.

The hot landing probably explains Elon's "fate" tweet from last week, then.  Maybe a three-engine landing burn again, and they've never yet only once been successful with that.

EDIT: from the launch log, only 4 attempts at multi-engine burns:
SES-9: 3-engine burn, unsuccessful.
JCSAT-14: 3-engine burn, successful.
Thaicom-8: 1-3-1 burn, successful. (Not a 3-engine *landing* burn AIUI.)
Eutelsat 117W: 3-engine burn, unsuccessful.

This landing is apparently "hot".  SES-9 was a 3-engine landing burn that took out OCISLY from space.  "Fate" could be simply referring to the narrow-margin landing attempt on this launch.

I hope OCISLY's clover is working!
« Last Edit: 03/29/2017 01:16 AM by cscott »

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 28475
  • Minnesota
  • Liked: 8347
  • Likes Given: 5482
Re: Fairing reuse
« Reply #730 on: 03/29/2017 01:12 AM »
It's not fairing recovery I think he'll be talking about, but our roomba friend. My main point has always been that the thing he's referring to in the tweet is not just reuse of the first stage.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online Semmel

  • Full Member
  • ****
  • Posts: 1456
  • Germany
  • Liked: 1253
  • Likes Given: 3414
Re: Fairing reuse
« Reply #731 on: 03/29/2017 06:29 AM »
My main point has always been that the thing he's referring to in the tweet is not just reuse of the first stage.

I am pretty sure it is first stage reuse. It's the one thing that is disruptive of the launch industry. It's the one thing the success of SpaceX will hinge on. I mean not this flight particularly but reuse in general. This flight is the first occasion where proving reuse is possible and maybe even economic. Any other technical challenge like fairing reuse will not determine SpaceXs future. But reuse must work or SpaceX has failed. That's why (in my opinion) musk is talking about fate.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7578
  • Everyplaceelse
  • Liked: 1169
  • Likes Given: 7826
Re: Fairing reuse
« Reply #732 on: 03/29/2017 06:38 AM »
I associate a "hot" landing with a stage that has pushed the rest of the stack to higher velocity or altitude than usual missions.

It will therefor be coming in at a faster velocity. OTOH it had to burn harder on launch suggests it will also have tighter restrictions on how much landing propellant it can carry.

So propellant margins are tight and the terminal landing process is shorter than usual. That means this time round engines really need to start at the first attempt and burn at full planned thrust for the full duration. It's unlikely the landing legs can soak up much of the KE left if the engines do their part fully.

All of which will make for very exciting video.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7578
  • Everyplaceelse
  • Liked: 1169
  • Likes Given: 7826
Re: Fairing reuse
« Reply #733 on: 03/29/2017 06:41 AM »
TBH I've never really understood need for the very rigid, heavy fairings that LV's use.

I've often wondered if you could get by with an inflatable design, soft of like those emergency half circular shelters, but with two edge to edge and both on end.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Kaputnik

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2831
  • Liked: 475
  • Likes Given: 444
Re: Fairing reuse
« Reply #734 on: 03/29/2017 11:36 AM »
TBH I've never really understood need for the very rigid, heavy fairings that LV's use.

I've often wondered if you could get by with an inflatable design, soft of like those emergency half circular shelters, but with two edge to edge and both on end.

 Seriously? For max Q, we're talking around mach 1 and airliner cruising altitude. That's a pretty tough gig. I don't see too many inflatable supersonic aircraft going about.
Waiting for joy and raptor

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7578
  • Everyplaceelse
  • Liked: 1169
  • Likes Given: 7826
Re: Fairing reuse
« Reply #735 on: 03/29/2017 01:05 PM »
TBH I've never really understood need for the very rigid, heavy fairings that LV's use.

I've often wondered if you could get by with an inflatable design, soft of like those emergency half circular shelters, but with two edge to edge and both on end.

 Seriously? For max Q, we're talking around mach 1 and airliner cruising altitude. That's a pretty tough gig. I don't see too many inflatable supersonic aircraft going about.
The difference between launch and cruise.  During launch dynamic pressure is quoted in pounds per sq foot because the rise in terms of psi (IE 1/144 smaller) is pretty small. I could see the need for a rigid fairing if there is a real fear of impact damage to the outside of the payload or if the fairing has inside ties to the payload to keep in place. 

The former is a real threat but the latter is not done AFAIK, even for payloads that require "vertical launch" due to the fragility of some of their components.

A lot of common practice in this industry seems to have evolved during the development of ICBMs.

I'd also point out that Joseph Kittinger and Felix Baumgarntner have gone supersonic in free fall inside nothing but a flexible sack (or "pressure suit" as I like to call it   :)  ).

Rigid nose cones assured the aerodynamics and their weight was acceptable. But LV's don't sit in silos for decades with staff walking around them periodically for inspection that might damage their payloads by dropping tools on them. The best way to protect a payload is inside a vehicle assembly building, followed by a transfer to the pad and a launch ASAP.

The two issues I can see are the very high noise levels and maintaining a controlled environment, which means making it pressure tight to slightly above atmospheric pressure.

Very little in this industry is original so I'd love to find some NASA report from the 1960's that looked at this and explains why it's unrealistic but so far all I've found is a brief discussion from 2015.

BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Kaputnik

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2831
  • Liked: 475
  • Likes Given: 444
Re: Fairing reuse
« Reply #736 on: 03/29/2017 05:21 PM »
The notion that we only see PLFs because that's what works for an ICBM seems a bit unrealistic. I'm sure the question of payload fairing mass, and how to reduce it, has been given at least *some* consideration by aerospace engineers over the last five decades.

But let's consider an inflatable fairing. It would be a pressure-stabilised structure, which we know works well on tankage. However propellant is incompressible so you can fairly pump up the tank pressure. A payload designed to operate in a vacuum would need to also be rated for the pressure of the inflated fairing (assuming a single skin structure). This pressure would be whatever max-Q is plus whatever is needed to make the PLF completely rigid and aerodynamically stable. That's got to be a fair bit of pressure...
Waiting for joy and raptor

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32426
  • Cape Canaveral Spaceport
  • Liked: 11164
  • Likes Given: 331
Re: Fairing reuse
« Reply #737 on: 03/29/2017 05:37 PM »
A lot of common practice in this industry seems to have evolved during the development of ICBMs.


Wrong, single warhead ICBM's have no need for fairings
« Last Edit: 03/29/2017 05:43 PM by Jim »

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32426
  • Cape Canaveral Spaceport
  • Liked: 11164
  • Likes Given: 331
Re: Fairing reuse
« Reply #738 on: 03/29/2017 05:40 PM »
I could see the need for a rigid fairing if there is a real fear of impact damage to the outside of the payload or if the fairing has inside ties to the payload to keep in place. 


Neither are applicable.

Offline matthewkantar

  • Full Member
  • ****
  • Posts: 847
  • Liked: 547
  • Likes Given: 662
Re: Fairing reuse
« Reply #739 on: 03/29/2017 05:45 PM »
Having to be rated for pressure would seem less consequential than having to be rated for rapid decompression. Fairings let the pressure drop as the rocket climbs. With an inflatable fairing, you would need to maintain the correct pressure differential until the faring is unneeded, then figure out how to get rid of it in a reliable way, not by popping it like a balloon. The valving problem seems doable if problematic. The disposal part less so.

I suppose an inflatable fairing could be an envelope that is inflated, leaving the resulting cavity at ambient pressure. It could have two halves that meet at rigid frames and separate as normal, but any weight savings start to disappear with rigid structure, hardware, and two layers of material.

Matthew

edit, fixed typo, 3.29.17 1:49 edt
« Last Edit: 03/29/2017 05:49 PM by matthewkantar »

Tags: