SpaceX F9 - 5th Reuse - Iridium Next 31-40 - SLC-4E

[Grendal]

5th Reuse Launch - Booster is Block 3 originally used for Iridium 2 on June 25th
Launch Date: December 22, Friday (Dec 23, Saturday GMT)
Launch time: 0126 GMT on 23rd (8:26 p.m. EST; 5:26 p.m. PST on 22nd)
Launch site: SLC-4E, Vandenberg Air Force Base, California
Booster Recovery: ASDS

This is the fourth set of 10 Iridium satellites to be launched this year. Iridium will bookend this years launch schedule, being the first and the last of the year.

This will be the 18th launch of the year, with the 15th booster recovered, and the 5th booster to be reused.

Overall, this will be the 45th Falcon 9 launched and the 21st booster recovered.

 

[Kipernicus]

At first I read the title to mean that this particular booster had gone up 4 times already and this is the 5th time.
Sounds more like this is just the 5th launch to feature a reused booster.
Still pretty cool.

 

[Cosmacelf]

Yeah, so far they’ve only (only!) used flight proven boosters once extra, so two flights per booster. They must have quite a nice stockpile of boosters by now!

When I toured SpaceX a few years ago, I was impressed by how much they were making the construction of rockets a rapid assembly line kind of thing (well, more of an assembly line than how you normally build rockets).

With all these flight proven cores, I wonder at what point they will slow down falcon 9 and dragon manufacturing? I wonder if the design of the BFR is far enough along that they can start building pieces of that soon?

 

[macpacheco]

We had a "stealthy" static fire...

SpaceX‏Verified account @SpaceX

Static fire test of Falcon 9 complete—targeting December 22 launch of Iridium-4 from Vandenberg AFB in California.

9:49 PM - 17 Dec 2017

 

[Grendal]

This just in. There will be no booster recovery happening for this launch. The reason they aren't trying to recover the booster is a secret. The information comes from Matt Desch:

Matt Desch on Twitter

It's not weight and not a special maneuver for satellite deployment.

 

[ecarfan]

Yes, I saw that earlier today. Interesting. I think perhaps Desch simply doesn’t know the reason or doesn’t feel like it is his place to say, it’s up to SpaceX.

It may simply be that SpaceX sees no logical reason to recover this Block 3 booster since it will have been flown multiple times.

 

[macpacheco]

Yes, I saw that earlier today. Interesting. I think perhaps Desch simply doesn’t know the reason or doesn’t feel like it is his place to say, it’s up to SpaceX.

It may simply be that SpaceX sees no logical reason to recover this Block 3 booster since it will have been flown multiple times.

Agreed. SpaceX might try for a 3rd flight on Block IVs, but probably not Block IIIs.
SpaceX has as many boosters as it wishes to have on storage. It needs to make room for the likely next 2 or 3 new Block IVs it should recover and then the Block Vs.
It would however make a lot more sense to expend Block IIIs on GTO missions where the maximum performance can make a big difference in saved fuel by shifting raising/circularization fuel to stationkeeping (often adding 5-10 years in useful life).

 

[ggr]

Disposal at sea is cheap...

 

[Grendal]

Yes, I saw that earlier today. Interesting. I think perhaps Desch simply doesn’t know the reason or doesn’t feel like it is his place to say, it’s up to SpaceX.

It may simply be that SpaceX sees no logical reason to recover this Block 3 booster since it will have been flown multiple times.

There was a lengthy discussion about this on Facebook SpaceX. The consensus is that recovery is not necessary because it is a Block 3 doesn't make sense. At the very least you'd want to recover the boosters nine Merlin engines. There are probably lots of other parts that are worth scavenging or recycling off the booster as well.

So I don't see SpaceX tossing away even an obsolete booster without a very good reason.

We know the reason is not because of an extra long burn for a special orbit. We also know it isn't because something is extra heavy with the primary payload. Both of those reasons came from Mr. Desch. The implication from the various tweets was that the reason came from SpaceX. I think he knows but isn't willing to say because it is something SpaceX let him know in confidence as you surmised.

My guess is that SpaceX is focusing on fairing recovery for this launch. Recovering the booster might somehow interfere with recovering the fairing in this instance. I think we will probably find out the reason during the webcast.

 

[ecarfan]

Recovering the booster might somehow interfere with recovering the fairing in this instance.

If that is the case, then the reasoning is beyond me. Booster separation and fairing separation are independent events that occur at different times. The ship that recovers the booster is not the same ship that will attempt to recover the fairing halves, and the two ships will surely be far apart.

I hope we find out the reason during the webcast, but I’m not counting on it.

 

[mongo]

There was a lengthy discussion about this on Facebook SpaceX. The consensus is that recovery is not necessary because it is a Block 3 doesn't make sense. At the very least you'd want to recover the boosters nine Merlin engines. There are probably lots of other parts that are worth scavenging or recycling off the booster as well.

So I don't see SpaceX tossing away even an obsolete booster without a very good reason.

We know the reason is not because of an extra long burn for a special orbit. We also know it isn't because something is extra heavy with the primary payload. Both of those reasons came from Mr. Desch. The implication from the various tweets was that the reason came from SpaceX. I think he knows but isn't willing to say because it is something SpaceX let him know in confidence as you surmised.

My guess is that SpaceX is focusing on fairing recovery for this launch. Recovering the booster might somehow interfere with recovering the fairing in this instance. I think we will probably find out the reason during the webcast.

Does the maritime exclusion zone for a RTLS preclude a fairing catching ship?
If the block 4/5 mods are engine related, then the block 3 usefulness is less.

Other thought: could the sacrifice of the 1st stage be done to give the 2nd stage more fuel after primary mission for new capability tests? For instance, leave the 2nd stage up there for a long time and test engine/ system functions (would need extra battery capacity since there are no panels). Could the 2nd stage itself be a useful satellite?

 

[Grendal]

Does the maritime exclusion zone for a RTLS preclude a fairing catching ship?
If the block 4/5 mods are engine related, then the block 3 usefulness is less.

Other thought: could the sacrifice of the 1st stage be done to give the 2nd stage more fuel after primary mission for new capability tests? For instance, leave the 2nd stage up there for a long time and test engine/ system functions (would need extra battery capacity since there are no panels). Could the 2nd stage itself be a useful satellite?

Does maritime exclusion prevent a ship from attempting a recovery? Probably not. There is a ship in the vicinity of the ASDS for powered landings. So I don't see why another ship for fairing recovery wouldn't be allowed for either RTLS or ASDS landings. I can't say for certain but it makes sense.

Block 3/4/5. Agreed. The usefulness for Block 3 is less but I would be very surprised if the cost of recovery isn't easily covered by the value of what is recovered even if it is obsolete. Each Merlin engine is supposed to be worth about $1 million each. It's a major reason the booster stage is a significant part of the rocket cost. Also, it would degrade SpaceX's recovery argument if you don't try to recover everything possible unless you have a very good reason behind it. So I expect there is a very good reason to let this booster be expended.

An experiment with second stage recovery or second stage advancement is also a good reason to lose a booster stage. I like that possibility too.

Second stage satellite? No clue. Interesting idea. Even if you generalize it to doing something useful with a used second stage is intriguing. Most ideas like this want to combine second stages together into a space station. The problem with that is getting pieces to come together. That takes fuel that those second stages no longer have. Using it as an object in orbit for some other activity is much more interesting. Very cool.

Like ecarfan, I'm hoping we find out the reason in the webcast.

 

[Grendal]

Webcasts -
Everyday Astronaut for interactive commentary on the launch:

 

[Grendal]

It looks like SpaceX will be doing an experiment on second stage recovery. That is probably why they aren't trying to recover the booster this time. Here is a picture of the rocket at Vandenberg on the pad. You can see the little mini grid fins.

 

[mongo]

It looks like SpaceX will be doing an experiment on second stage recovery. That is probably why they aren't trying to recover the booster this time. Here is a picture of the rocket at Vandenberg on the pad. You can see the little mini grid fins.
View attachment 268116

Unless I'm not seeing the fins you are talking about, that looks like the normal fin position to me.

Edit: unless they put them on a detachable interstage and will recombine the fairing around the interstage in space for reentry? (which covers the issue of catching two fairing halves in one net on Mr Steve)

 

[scaesare]

I'm not sure I see the mini-fins being spoken of either.

I see the normal booster fin. I also see many small squares around the base of the fairing (not sure what those are). But I'm not seeing anything on the second stage body that looks like grid fins to me.

Mind posting an annotated crop of what you mean?

 

[Grendal]

Webcast:

I'm not sure I see the mini-fins being spoken of either.

I see the normal booster fin. I also see many small squares around the base of the fairing (not sure what those are). But I'm not seeing anything on the second stage body that looks like grid fins to me.

Mind posting an annotated crop of what you mean?

The fins just looked smaller to me. I suppose I'm wrong about that....

If they are the regular size then it's very interesting that this booster has grid fins but no landing legs. SpaceX is definitely doing some sort of experiment here.

 

[Electroman]

They put the fins initially for a landing, and then when they decided not to land, they just didn't bother to remove the fins, but only removed the legs to save some weight.

Sometimes the most simple explanation is the correct one !

[I just made it up]

 

[mongo]

They put the fins initially for a landing, and then when they decided not to land, they just didn't bother to remove the fins, but only removed the legs to save some weight.

Sometimes the most simple explanation is the correct one !

[I just made it up]

I read that the legs get removed after every flight. Removing fins would leave a hole, and take extra effort.

 

[scaesare]

Webcast:

The fins just looked smaller to me. I suppose I'm wrong about that....

If they are the regular size then it's very interesting that this booster has grid fins but no landing legs. SpaceX is definitely doing some sort of experiment here.

Ah... I misinterpreted your comments to mean fins on the second stage for a recovery experiment there. Thanks.