Author Topic: SpaceX Falcon 9 : PAZ & Microsat 2a/2b : SLC-4E : Feb 22, 2018 : DISCUSSION  (Read 202441 times)

Offline meekGee

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I guess they could try to fly the fairing over at some low (very low) altitude then release the chutes at the right time. The fairing would drop predictably into the net. Maybe.
Very low, yes.  A near miss. 

This way you need to get less things right, since it doesn't matter how fast you're overtaking the boat. In exchange, you need to cut the cord when the ballistic IIP hits the net.

Clearly the ship is helping to catch the fairing.  Ships capable of 32 knots are expensive.

The overtaking speed matters a lot.   In the reference frame of the boat, the angle of the incoming fairing is tan-1(V_sink_fairing /(V_forward_fairing - Vship)).  If the ship can keep up with the fairing, then it appears to descend vertically.  Even if can only half keep up with the fairing, it roughly doubles the angle (from horizontal) and thus doubles the cross sectional area of the net.

I think they will control the fairing all the way into the net.  The tradeoff is the ability to make last minute corrections vs the chance of a last minute gust pushing you off course.   Human parachuters control all the way to the ground without seeming problems, and the air should be even more predictable at sea, and high up like the net.  Plus assuming the ship keeps a course into the wind, the large added constant component reduces the relative size of the gusts.  In addition, with this approach you can stall the parachute for the last second of flight, which reduces impact loads.  This is important for people, and might be a consideration for the fairing.
Air gusts at sea will be worse than air in a stadium on a calm day.

I'm sure the ship cooperates and makes itself an "easy target", as requested by the chute..  But in the end, I think it's a bombing run. 

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Offline LouScheffer

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Air gusts at sea will be worse than air in a stadium on a calm day.

There must be literally millions of hours of data on exactly this, since this is what aircraft carriers have done since they were invented.  32 knots into the wind, and then care a great deal about the air conditions a few tens of meters above the water.  And they do this in all kinds of weather, not just calm days.  They fly the plane right down to the deck.

Offline fthomassy

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Air gusts at sea will be worse than air in a stadium on a calm day.

There must be literally millions of hours of data on exactly this, since this is what aircraft carriers have done since they were invented.  32 knots into the wind, and then care a great deal about the air conditions a few tens of meters above the water.  And they do this in all kinds of weather, not just calm days.  They fly the plane right down to the deck.
And the ship at speed may have a stabilizing effect on final approach. The complication is Mr. Stephen is not very flat.
gyatm . . . Fern

Offline meekGee

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Air gusts at sea will be worse than air in a stadium on a calm day.

There must be literally millions of hours of data on exactly this, since this is what aircraft carriers have done since they were invented.  32 knots into the wind, and then care a great deal about the air conditions a few tens of meters above the water.  And they do this in all kinds of weather, not just calm days.  They fly the plane right down to the deck.
Well you hardly have the option of cutting the fuselage loose from the wings, hitting the deck, and declaring victory, do you...

Plus the airplane is nothing like a parafoil to begin with.

And, they occasionally miss.

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Offline AJW

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One way to get these issues figured out might be lots of practice using air drops rather than just one trial per launch.   A fairing half would be a tight fit for a C-5 or there might be a way to lift an entire fairing with an aircraft like the White Knight Two...  Richard did say he felt a bit jealous after the FH launch. 
We are all interested in the future, for that is where you and I are going to spend the rest of our lives.

Offline Comga

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The discussion of fairing recovery in general is thoroughly covered, and much more appropriate, over in the dedicated “Fairing Recovery “ thread.

I just wore a post about the targeting over there:
https://forum.nasaspaceflight.com/index.php?topic=37727.msg1792783#msg1792783
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline su27k

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So Elon said about 1-2 hours post-launch that the sats will fly over LA about 22 hours after launch and try to send down "Hello world".

Do we know how this went? Radio silence as it usual with Starlink?

From https://www.reddit.com/r/spacex/comments/803ty9/starlink_will_be_simpler_than_ipv6_and_have_tiny/duu8bdk/:

Quote
My SpaceX friends confirmed that the message was successful. Rajeev (VP of satellite development) emailed Elon informing him of its successful transmission, and Elon forwarded the email to the entire company with a congratulatory message to all.
« Last Edit: 02/26/2018 06:12 am by su27k »

Offline Nomadd

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I guess why wouldn't the ship move to where the parachute seems to be guiding the fairing, rather than hold a fixed position? Baseball analogy, the fielder moves to get under the ball as they understand the ball's likely arrival point better and better.
A baseball isn't trying to guide itself to the glove. Both the ship and the fairing trying to guide themselves to the other could be a real mess. That parafoil has to be active control or it wouldn't hit within miles of the target.
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline LouScheffer

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I guess why wouldn't the ship move to where the parachute seems to be guiding the fairing, rather than hold a fixed position? Baseball analogy, the fielder moves to get under the ball as they understand the ball's likely arrival point better and better.
A baseball isn't trying to guide itself to the glove. Both the ship and the fairing trying to guide themselves to the other could be a real mess. That parafoil has to be active control or it wouldn't hit within miles of the target.

I think the parafoil guides itself to roughly the right spot.  Then it and the boat both line up on final.  To see how this might work, check out this video of a parachutist landing on a moving truck.  He gets to roughly the right spot, then lines up on the truck, which drives straight and a little slower than the forward speed of the parachute.

Offline JJB

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Ok, JB is a bit of a showoff, but this video shows the maneuverability and precision that modern paragliders are capable of.
https://www.youtube.com/user/jbintheairintheair

 
There is probably still life clinging to thermal vents, giggling about the absurdity of growing a backbone.-KZ.

Offline JimO

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Here's my draft report on the ground observations of the second stage deorbit burn. I hope everybody here got proper credit for their contributions.

Offline gongora

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Satellites have changed parameters since launch, is this due to propulsion or just normal drift?


Tintin A
Perigee: From 500 to 505.3 km 
Apogee: From 517  to  525.7 km 

Tintin B
Perigee: From 499 to 505.2 km 
Apogee: From 517  to 525.0 km

They are supposed to eventually raise their orbit by about 500km.

Offline wannamoonbase

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Satellites have changed parameters since launch, is this due to propulsion or just normal drift?


Tintin A
Perigee: From 500 to 505.3 km 
Apogee: From 517  to  525.7 km 

Tintin B
Perigee: From 499 to 505.2 km 
Apogee: From 517  to 525.0 km 


They seem to match pretty closely.  Wouldn't drift vary more between the two?
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline vaporcobra

One step further (at least AFAIK), it would require propulsion to "drift" upstream in the case of raising orbits.
« Last Edit: 03/30/2018 06:18 am by vaporcobra »

Offline deruch

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Can't "drift" upwards from LEO, so it was propulsion.  Unless the changes represent a refinement of the tracked orbit by JSpOC, but given the length of time they have already been in orbit this seems unlikely.  Any such refinement should have only taken a relatively small number of orbits, not a month of them.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline AncientU

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Can't "drift" upwards from LEO, so it was propulsion.  Unless the changes represent a refinement of the tracked orbit by JSpOC, but given the length of time they have already been in orbit this seems unlikely.  Any such refinement should have only taken a relatively small number of orbits, not a month of them.

Ion thruster check-out?
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Offline Craig_VG

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Can't "drift" upwards from LEO, so it was propulsion.  Unless the changes represent a refinement of the tracked orbit by JSpOC, but given the length of time they have already been in orbit this seems unlikely.  Any such refinement should have only taken a relatively small number of orbits, not a month of them.

That's what I was wondering, thanks!

Offline Flying Beaver

Not to be one-upped by the fancy new Iridium-5 fairing half, PAZ's recovered fairing has made an appearance at Berth 240, SpaceX's prospective BFR factory and recovery facility. It's visibly being scrapped where it sits - all interior components are being removed and stacked on the ground. ¯\_(ツ)_/¯

Or it's being prepped for helicopter drop tests mention by Elon.

Otherwise that's quite the waste of the perfect test article.

Watched B1019 land in person 21/12/2015.

Offline vaporcobra

Not to be one-upped by the fancy new Iridium-5 fairing half, PAZ's recovered fairing has made an appearance at Berth 240, SpaceX's prospective BFR factory and recovery facility. It's visibly being scrapped where it sits - all interior components are being removed and stacked on the ground. ¯\_(ツ)_/¯

Or it's being prepped for helicopter drop tests mention by Elon.

Otherwise that's quite the waste of the perfect test article.

Can't say more, but it's almost certainly no longer a viable structural test article.

Offline Johnnyhinbos

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Not to be one-upped by the fancy new Iridium-5 fairing half, PAZ's recovered fairing has made an appearance at Berth 240, SpaceX's prospective BFR factory and recovery facility. It's visibly being scrapped where it sits - all interior components are being removed and stacked on the ground. ¯\_(ツ)_/¯

Or it's being prepped for helicopter drop tests mention by Elon.

Otherwise that's quite the waste of the perfect test article.

Can't say more, but it's almost certainly no longer a viable structural test article.
Nicely done Vaporcobra. I must say, Teslarati has been doing an excellent SpaceX sleuthing job as of late!

And - to add to that...

I investigated the photo with the guy in the SpaceX hoodie. Behind him is a new crate with the following painted on the side...

“The leader in precisi...” and what looks like the logo “MM (superscript) I”.

lol and behold - MMIST!

“The leader in aerial precision delivery”

http://mmist.ca

So look who developed the recovery system!
« Last Edit: 04/01/2018 09:59 pm by Johnnyhinbos »
John Hanzl. Author, action / adventure www.johnhanzl.com

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