Author Topic: Fairing reuse  (Read 509795 times)

Offline BeamRider

  • Member
  • Posts: 62
  • Seattle
  • Liked: 24
  • Likes Given: 7
Re: Fairing reuse
« Reply #1140 on: 12/26/2017 11:52 AM »
So you're thinking these are the support arms for a set of "bouncy castle walls" that funnel the faring(s) into the centre?

Yes. A ďnetĒ approach (my first assumption too) has problem that I am trying to work around:
1. You cannot catch both fairings at once without potential interference.
2. You cannot catch both sequentially without potentially damaging contact of one fairing landing and laying on the other.
3. Any scheme for moving one out of the way or somehow protecting it, and then catching the other to avoid 2 will have to be completed very quickly. Itís hard to imagine the degree of control over the timing of the landing via alternate parachute paths, or Angle of Attack, exceeding a minute, but this is just a guess

Offline meekGee

  • Senior Member
  • *****
  • Posts: 8178
  • N. California
  • Liked: 4418
  • Likes Given: 868
Re: Fairing reuse
« Reply #1141 on: 12/26/2017 12:24 PM »
So you're thinking these are the support arms for a set of "bouncy castle walls" that funnel the faring(s) into the centre?

Yes. A ďnetĒ approach (my first assumption too) has problem that I am trying to work around:
1. You cannot catch both fairings at once without potential interference.
2. You cannot catch both sequentially without potentially damaging contact of one fairing landing and laying on the other.
3. Any scheme for moving one out of the way or somehow protecting it, and then catching the other to avoid 2 will have to be completed very quickly. Itís hard to imagine the degree of control over the timing of the landing via alternate parachute paths, or Angle of Attack, exceeding a minute, but this is just a guess
My guess is two boats, but there is the possibility of buying a few minutes by opening the chutes at very different times.

Still though - a fairing is worth so much more than the amortized cost of the boat, so two boats makes more sense to me.
ABCD - Always Be Counting Down

Online AncientU

  • Senior Member
  • *****
  • Posts: 6113
  • Liked: 3905
  • Likes Given: 5392
Re: Fairing reuse
« Reply #1142 on: 12/26/2017 12:27 PM »
To me inflatable structures seem quite a bit more hassle to operate and maintain than appropriately tensioned nets. Itís not clear to me how significant the benefit(s) of using inflatables?
Agreed.  The four arm structure, to me, says "non elastic web".

If there's controlled give to it, it's created by controlling the tension in four cables coming down from pulleys at the apexes using brake winches.

Looking closely at the ship rigging, it could be that the port pair and the starboard pair deploy 'bouncy castles' to their respective sides of the ship.  The forward arms look to be articulated in the lower section (shown straight in the image) and the aft arms look like they have a brace on deck for them to rest on when lowered past horizontal outboard.  This would create a pair of landing beds nicely separated by the width of the ship.

https://forum.nasaspaceflight.com/index.php?topic=37727.1020
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline meekGee

  • Senior Member
  • *****
  • Posts: 8178
  • N. California
  • Liked: 4418
  • Likes Given: 868
Re: Fairing reuse
« Reply #1143 on: 12/26/2017 12:30 PM »
To me inflatable structures seem quite a bit more hassle to operate and maintain than appropriately tensioned nets. Itís not clear to me how significant the benefit(s) of using inflatables?
Agreed.  The four arm structure, to me, says "non elastic web".

If there's controlled give to it, it's created by controlling the tension in four cables coming down from pulleys at the apexes using brake winches.

Looking closely at the ship rigging, it could be that the port pair and the starboard pair deploy 'bouncy castles' to their respective sides of the ship.  The forward arms look to be articulated in the lower section (shown straight in the image) and the aft arms look like they have a brace on deck for them to rest on when lowered past horizontal outboard.  This would create a pair of landing beds nicely separated by the width of the ship.

https://forum.nasaspaceflight.com/index.php?topic=37727.1020

That's interesting, hadn't thought of that.

EDIT:  But on further reflection and inspection of the image, I'm sticking with my original theory:

- Fixed arms.
- Inelastic web + pulleys, controlled sag via tension rope and brake pulley.
- Parachute system overtakes the ship, intersects its path, and "misses high".
- Parachute system drops the fairing-half into the net.
- OBPFH.
« Last Edit: 12/26/2017 12:55 PM by meekGee »
ABCD - Always Be Counting Down

Offline JamesH65

  • Full Member
  • ****
  • Posts: 781
  • Liked: 493
  • Likes Given: 8
Re: Fairing reuse
« Reply #1144 on: 12/26/2017 01:11 PM »
I like the bouncing castle/net chute idea. First fairing lands, slides down the chute, grabbed/slides on to dolly at bottom and moved out of the way. Second lands (easily delayed by an earlier parachute opening and/or a different number of parachutes.) and slides down to join the first.

Or how about two chutes on the net, and you just cover the first one once the first fairing has arrived, so the second slides down the second one.

I suspect there are a number of ways of arranging capture of two fairing with one boat.

« Last Edit: 12/26/2017 01:13 PM by JamesH65 »

Offline alang

  • Full Member
  • **
  • Posts: 221
  • Liked: 78
  • Likes Given: 6
Re: Fairing reuse
« Reply #1145 on: 12/26/2017 02:35 PM »
If you were designing a general purpose cradle landing structure that could also be used for dragon capsules as well as fairings then could this be it? I could imagine the attempt being made for the cargo version. I'm assuming that avoiding salt water might be a good thing, even for something designed for it.

Offline octavo

  • Full Member
  • *
  • Posts: 116
  • Liked: 50
  • Likes Given: 102
Re: Fairing reuse
« Reply #1146 on: 12/26/2017 04:24 PM »
If you were designing a general purpose cradle landing structure that could also be used for dragon capsules as well as fairings then could this be it? I could imagine the attempt being made for the cargo version. I'm assuming that avoiding salt water might be a good thing, even for something designed for it.
Not unless they changed the round parachutes currently used, for steerable parafoils.

With round chutes, steering control is very limited, making a precise landing nearly impossible.

ETA: how much do fairings weigh compared to a returning dragon? Probably the bouncy bag would have to be yuuuge to handle dragon too.
« Last Edit: 12/26/2017 04:26 PM by octavo »

Offline IanThePineapple

Re: Fairing reuse
« Reply #1147 on: 12/26/2017 04:26 PM »
If you were designing a general purpose cradle landing structure that could also be used for dragon capsules as well as fairings then could this be it? I could imagine the attempt being made for the cargo version. I'm assuming that avoiding salt water might be a good thing, even for something designed for it.

Landing a Dragon on a dry net would probably be super helpful, the heat shield and the many Dracos would be in much greater condition than they would be in saltwater.

Offline Kansan52

  • Full Member
  • ****
  • Posts: 1067
  • Hutchinson, KS
  • Liked: 325
  • Likes Given: 374
Re: Fairing reuse
« Reply #1148 on: 12/26/2017 04:37 PM »
Wamore was used on the Stig B and nearly landed on the launch site:


Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 10065
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 6886
  • Likes Given: 4678
Re: Fairing reuse
« Reply #1149 on: 12/26/2017 04:44 PM »
Landing a Dragon on a dry net would probably be super helpful, the heat shield and the many Dracos would be in much greater condition than they would be in saltwater.
Would the netting material need to be heat resistant? Does the heat shield have sufficient time (the airflow presumably is good) to cool down? What about the thruster ports? (if not fired, then presumably yes?)
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline octavo

  • Full Member
  • *
  • Posts: 116
  • Liked: 50
  • Likes Given: 102
Re: Fairing reuse
« Reply #1150 on: 12/26/2017 05:08 PM »
Landing a Dragon on a dry net would probably be super helpful, the heat shield and the many Dracos would be in much greater condition than they would be in saltwater.
Would the netting material need to be heat resistant? Does the heat shield have sufficient time (the airflow presumably is good) to cool down? What about the thruster ports? (if not fired, then presumably yes?)
Would several minutes under a parachute be enough? The heat of reentry is intense, but relatively short duration.

Offline rberry

  • Member
  • Posts: 32
  • Houston
  • Liked: 23
  • Likes Given: 39
Re: Fairing reuse
« Reply #1151 on: 12/27/2017 06:08 AM »
Mr. Steven is a relatively fast moving vessel for its size. If you attach any number of large bouncy castles to the rear of the vessel (in the water or suspended in the air), then she won't be able to utilize her speed due to the increased drag. At that point it would be cheaper to use a slower moving vessel of the same size. Whatever is suspended from the masts will likely not inhibit the vessels speed (its primary asset over other vessels). Something net like.
« Last Edit: 12/27/2017 06:09 AM by rberry »
-Ryan

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7320
  • Everyplaceelse
  • Liked: 1072
  • Likes Given: 7191
Re: Fairing reuse
« Reply #1152 on: 12/27/2017 08:16 AM »
Would several minutes under a parachute be enough? The heat of reentry is intense, but relatively short duration.
IIRC one of the attractions of PICA is it's both quite low density and a poor thermal conductor. This means
a) The reentry heat stays in a layer near the surface and
b) There is (relatively) less of it than with older ablators.

Treat the heat as a fluid and PICA like a sponge. Several minutes falling through fairly dense, cold air below M1 should certainly "evaporate" the heat from the surface layer. The remaining heat (deeper below the surface) will then split. Some diffuses inwards, some back to the surface.

Exactly how long that process lasts, how many Joules need to be shed and what the surface temp of the heatshield will be when it hits the nets/inflated walls are why you run FEA software.
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 So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 10065
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 6886
  • Likes Given: 4678
Re: Fairing reuse
« Reply #1153 on: 12/27/2017 11:55 AM »
This thread asked what the specific heat of PICA-X was, I don't think an answer was ever found.
https://forum.nasaspaceflight.com/index.php?topic=36039.0

I would suspect it was rather high but?

( High specific heat means more heat energy is needed per unit mass to raise the temperature of a material by one degree so it makes a better defense against heat energy. If the thermal conductivity is low that's a good thing too (while defending). This is a place where low density kind of works against you on heating up, but for you on cooling down again. Same with thermal conductivity... low works for you on heating and against you on cooling)
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline speedevil

  • Senior Member
  • *****
  • Posts: 2058
  • Fife
  • Liked: 1008
  • Likes Given: 1125
Re: Fairing reuse
« Reply #1154 on: 12/27/2017 01:37 PM »
Mr. Steven is a relatively fast moving vessel for its size. If you attach any number of large bouncy castles to the rear of the vessel (in the water or suspended in the air), then she won't be able to utilize her speed due to the increased drag

Umm...
From the specs Mr Steven has 10000hp - 7.2MW.
It can cruise at 16m/s.
This implies a drag of around 450000N.
At this airspeed, one square meter has about 150N of drag, worst case.
So, a 17 meter square sail, with its maximum area pointed at the wind will absorb a power equal to one tenth of the water drag.

This is quite a lot - the arms on the ship are ~25m from each other, even a ~5m*25m frontal area bouncy castle on top of the arms, with a hemicylindrical front will impact the speed by under 10%.

Offline JAFO

  • Full Member
  • ****
  • Posts: 587
  • Liked: 214
  • Likes Given: 169
Re: Fairing reuse
« Reply #1155 on: 12/27/2017 05:26 PM »
What about rebound? Even if it's moving slowly, something that big is going to land with a lot of energy, is there enough room to absorb it all or how could they keep the fairing from impacting and not bouncing off?

Anyone can do the job when things are going right. In this business we play for keeps.
ó Ernest K. Gann

Offline speedevil

  • Senior Member
  • *****
  • Posts: 2058
  • Fife
  • Liked: 1008
  • Likes Given: 1125
Re: Fairing reuse
« Reply #1156 on: 12/27/2017 05:35 PM »
What about rebound? Even if it's moving slowly, something that big is going to land with a lot of energy, is there enough room to absorb it all or how could they keep the fairing from impacting and not bouncing off?

This is pretty much a solved problem for people that work with ropes.
You don't have the net supported by elastic ropes, but comparatively rigid ones, and you have either a rope connected to a clutch that allows it to slip in one direction at a high controlled force (so, say if >10 tons, it will slip), but not return. Or a 'rip' mechanism that takes lots of energy to rip and stops the bounce.
is an example of a strap for fall arrest - this has two wide straps that are sewn together - ripping the stitches absorbs lots of energy, but it doesn't cause a bounce like elastic would.
« Last Edit: 12/27/2017 05:40 PM by speedevil »

Offline nacnud

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2214
  • Liked: 369
  • Likes Given: 177
Re: Fairing reuse
« Reply #1157 on: 12/27/2017 06:30 PM »
That is not reusable though, better to use the types of ropes used in climbing. In those the core of the rope is heat treated to make it crinkly. If a force is applied then the crinkles unfold to allow the rope to stretch. The normal ammount of stretch is 10% but it can be 30% or more. There is zero rebound.

In climbing the device described above is referred to as a screamer, it's used in situations where above a fixed amount of force the whole system would fail.

To catch a falling fairing I'd make a net out of dynamic rope (climbing rope) attached to the arms (as on Mr Stephens) with screamers. In normal operation the net alone would provide all the cushioning needed. In extreme situations the screamers would be triggered to protect the arms from failing but still allowing the fairing to be captured.

Offline meekGee

  • Senior Member
  • *****
  • Posts: 8178
  • N. California
  • Liked: 4418
  • Likes Given: 868
Re: Fairing reuse
« Reply #1158 on: 12/27/2017 07:49 PM »
That is not reusable though, better to use the types of ropes used in climbing. In those the core of the rope is heat treated to make it crinkly. If a force is applied then the crinkles unfold to allow the rope to stretch. The normal ammount of stretch is 10% but it can be 30% or more. There is zero rebound.

In climbing the device described above is referred to as a screamer, it's used in situations where above a fixed amount of force the whole system would fail.

To catch a falling fairing I'd make a net out of dynamic rope (climbing rope) attached to the arms (as on Mr Stephens) with screamers. In normal operation the net alone would provide all the cushioning needed. In extreme situations the screamers would be triggered to protect the arms from failing but still allowing the fairing to be captured.


Yup - the equivalent of the crush cores at end-of-travel for the landing legs on F9.

If the braking winch is electric, you actually have a record of how gently the fairing was caught, what was the maximum g on it, etc.  Crossing a certain limit would trigger a more detailed post-catch inspection.  (or actually any form of strain gauge would do)
ABCD - Always Be Counting Down

Offline speedevil

  • Senior Member
  • *****
  • Posts: 2058
  • Fife
  • Liked: 1008
  • Likes Given: 1125
Re: Fairing reuse
« Reply #1159 on: 12/28/2017 11:32 AM »

If the braking winch is electric, you actually have a record of how gently the fairing was caught, what was the maximum g on it, etc.  Crossing a certain limit would trigger a more detailed post-catch inspection.  (or actually any form of strain gauge would do)

Electric also lets you do things like vary the braking force so that per line it is a maximum of 30 tons, but the total is capped at 60 tons.
Or more advanced schemes aimed at catching it properly - for example, if it lands too far forward, you may want to slack off the back of the net almost entirely to avoid it being tipped out as the front drops.

Tags: