Author Topic: SpaceX Falcon 9 : Iridium NEXT Flight 4 : December 22/23, 2017 : Discussion  (Read 103480 times)

Offline cppetrie

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I was under the impression that all the satellites in the constellation were at the same inclination but in different planes/phases. Why would these require more performance than previous missions. Higher orbit maybe but they canít get that close to the operating orbit before risking a collision as the orbit are already populated. I also thought I remember that all of these sats in this launch were headed to the same plane except two that were planned as on orbit spares in different planes.

Iím a total amateur with this orbit stuff so it is entirely possible Iíve massively misunderstood something. The hazard areas seem largely consistent from launch to launch, though, which also has me thinking these launches are all very similar in performance requirements.

Offline Steven Pietrobon

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I'm puzzled by SpaceX's decision to expend this booster. We know from previous Iridium flights that the vehicle has enough performance for it to be recovered. If I had an excess of obsolete boosters, I wouldn't expend them on missions where they can be reused, like in this flight. I would save them for those missions where they have to be expended, like in high performance GTO missions.
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Offline pathfinder_01

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I'm puzzled by SpaceX's decision to expend this booster. We know from previous Iridium flights that the vehicle has enough performance for it to be recovered. If I had an excess of obsolete boosters, I wouldn't expend them on missions where they can be reused, like in this flight. I would save them for those missions where they have to be expended, like in high performance GTO missions.

Not really. There are costs associated with supporting an older model of booster and this one likely has maybe one more mission left in it. Given they have to build block V for commercial crew and given the likely limited storage, over supply of boosters and likely greater cost to refurbish getting rid of block III makes sense.

Offline hopalong

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I'm puzzled by SpaceX's decision to expend this booster. We know from previous Iridium flights that the vehicle has enough performance for it to be recovered. If I had an excess of obsolete boosters, I wouldn't expend them on missions where they can be reused, like in this flight. I would save them for those missions where they have to be expended, like in high performance GTO missions.

Not really. There are costs associated with supporting an older model of booster and this one likely has maybe one more mission left in it. Given they have to build block V for commercial crew and given the likely limited storage, over supply of boosters and likely greater cost to refurbish getting rid of block III makes sense.

My initial thoughts where the same as Steven's, that they would look to expend the last block III's and IV's on high energy missions. But this one is on the wrong coast as the high energy missions are launched from the cape. So another factor to include in the calculation is the cost of shipping the core across the States. It can't be cheap to move a core across the country.

IMHO, expending this core shows that SpaceX is a pragmatic company as well as a visionary one.


Offline woods170

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Expend the booster to save money.  Hmmmm. 

 - Ed Kyle
It's disappointing to me but how is expending a booster you plan to never use again confusing to people?  I'd prefer they recover it and analyze/recycle it. But they didn't ask me.

They don't need to analyse it. They have already recovered (and analyzed) boosters 20 times, 3 of them being re-flights. SpaceX right now has a huge database on booster wear-and-tear, and the information in that database has been essential for informing the design of Falcon 9 Block 5. In stead of analyzing yet another old Block 3 it is time to get the first Block 5 off the ground and validate its design.

One of the essentials of working agile (like SpaceX does) is never to get stuck in the past. Always move forward. That's what SpaceX is doing. Block 3 has been analyzed to death and is yesterday's booster. Time to let go of it.
Also, it doesn't help that SpaceX has no storage space for all those old booster. They've already begun dumping some of them in the boneyard section of McGregor.

Online MikeAtkinson

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We know that SpaceX perform minor experiments on most flights, especially after the main mission is complete. Perhaps on these next two flights the experiments mean that recovery is unlikely. I'm thinking things like multiple second stage relights after release of the satellites or high angle of attack reentries.

Offline Ben the Space Brit

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My guess is that, if the reason is performance-based, we need to look for this mission to have a lot higher-energy insertion orbit for some reason. Maybe a combination of launch date (which must have moved a few times) and schedule pressure (I understand that Iridium needs the entire constellation launched by the end of H1-2018) which leads this launch to be at a non-optimal time and requiring more energy to get the satellites to the desired orbit.
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Offline chalz

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A reusable booster is always going to fly as expendable on its last flight, no matter how long or short its flight history. It will keep happening until some financial penalty is applied for dropping this specific type of industrial waste in the ocean. Until then even a tiny cost to return the booster is greater than zero cost of letting it drop.

A reusable booster is always going to fly as expendable on its last flight, no matter how long or short its flight history. It will keep happening until some financial penalty is applied for dropping this specific type of industrial waste in the ocean. Until then even a tiny cost to return the booster is greater than zero cost of letting it drop.

I think the people at SpaceX really want to be better than that.
Once reuse matures and the boosters fly many missions I expect them to properly retire their beaten workhorses.
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Offline Ben the Space Brit

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A reusable booster is always going to fly as expendable on its last flight, no matter how long or short its flight history. It will keep happening until some financial penalty is applied for dropping this specific type of industrial waste in the ocean. Until then even a tiny cost to return the booster is greater than zero cost of letting it drop.

That depends on a lot of factors. It's quite possible that SpaceX will want to take units at the end of their fatigue life and cannibalise them for both scrap parts as well as rare alloys  that can be returned to their suppliers for re-smelting and re-forging.

I maintain my opinion that the expending of this booster on this flight is entirely a performance issue: the customer's target orbit leaves insufficient propellent margins for even a drone ship recovery.
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Offline codav

My guess is that, if the reason is performance-based, we need to look for this mission to have a lot higher-energy insertion orbit for some reason.

This is most probably not the case, Iridium satellites all go into almost the same orbit (polar, ~780km altitude for active satellites, 666km for spares), with a small height difference between each plane to avoid collisions over the poles. All previous launches deployed at around 680km, the satellites then perform the insertion into their respective final orbit, some even change the plane using orbital precession to assist with it, which takes a few months.

Offline JamesH65

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A reusable booster is always going to fly as expendable on its last flight, no matter how long or short its flight history. It will keep happening until some financial penalty is applied for dropping this specific type of industrial waste in the ocean. Until then even a tiny cost to return the booster is greater than zero cost of letting it drop.

That depends on a lot of factors. It's quite possible that SpaceX will want to take units at the end of their fatigue life and cannibalise them for both scrap parts as well as rare alloys  that can be returned to their suppliers for re-smelting and re-forging.

Only if the cost of recovering is less than the gains made by reuse. And we have no idea of the figures involved.

To me, this just seems to be a "We don't need this booster to come back" because a) we'll never use it b) We have no place to store it c) recovery costs exceed scrap value d) We'll have Block 5 soon making all previous models obsolete (see a) e) the longer we keep flying these older boosters, the longer before we start using block 5 which is cheaper

Offline Darga

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I'm puzzled by SpaceX's decision to expend this booster. We know from previous Iridium flights that the vehicle has enough performance for it to be recovered. If I had an excess of obsolete boosters, I wouldn't expend them on missions where they can be reused, like in this flight. I would save them for those missions where they have to be expended, like in high performance GTO missions.

Maybe they are expending it because JRTI is down for some reason and they cant RTLS yet.

Offline sevenperforce

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Expend the booster to save money.  Hmmmm. 

 - Ed Kyle
You so want to be right about the folly of reusable boosters... but you're not.
I've never called it "folly".  They may well be on a path to making partial reuse pay, eventually, but what I have been saying is that they are not there yet.  Throwing away a first stage on purpose during only its second flight (both lower energy LEO missions, BTW) is proof. 

 - Ed Kyle
This will be its third flight. Also, this is a polar orbit, on the higher end of LEO energies.

Online Johnnyhinbos

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Expend the booster to save money.  Hmmmm. 

 - Ed Kyle
You so want to be right about the folly of reusable boosters... but you're not.
I've never called it "folly".  They may well be on a path to making partial reuse pay, eventually, but what I have been saying is that they are not there yet.  Throwing away a first stage on purpose during only its second flight (both lower energy LEO missions, BTW) is proof. 

 - Ed Kyle
This will be its third flight. Also, this is a polar orbit, on the higher end of LEO energies.
Third?
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Offline sevenperforce

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This will be its third flight. Also, this is a polar orbit, on the higher end of LEO energies.
Third?
Whoops, my mistake. I read something wrong, earlier in the thread.

Offline Cheapchips

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Maybe they're using the extra margin for 2nd stage experiments?

(I'm not proposing anything exotic)
« Last Edit: 12/20/2017 02:33 PM by Cheapchips »

Offline hektor

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Maybe they could find a museum ready to provide it a new home ?

Online jpo234

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So why not give Iridium the most boost possible.

That's not a GEO launch. The satellites go to their initial orbit and don't need any additional boost beyond that.
You want to be inspired by things. You want to wake up in the morning and think the future is going to be great. That's what being a spacefaring civilization is all about. It's about believing in the future and believing the future will be better than the past. And I can't think of anything more exciting than being out there among the stars.

Offline gongora

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I guess the launch log entry for this will be "the one where Elon murdered the booster"  ::)

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