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2 minutes ago, cubinator said:

Does the booster really need cooling after landing? Sure, the engine bells are hot and the rocket just spent some time in supersonic wind, but right after that it spends a bunch of time in regular wind which tends to be cooling.

Also, water deluge systems are normally for dampening sound and vibration, and the booster isn't vibrating all that much sitting on the pad with its engines off.

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51 minutes ago, nasa legolas said:

I think they should use water deluge systems on the landing pad. you know, for cooling down the booster after landing. if they ever do it it would be a good water show.

Why, in god’s name? If they’ve survived heating up, trying to make them cool down rapidly would just cause undue thermal stress on the material.

You know, undermining reusability.

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Aside from being, admittantly, spectacular if they did that, what reason would they have to cool the booster that fast? They don't seem to have had issues with temperature recently, and thermal stress would be a very significant concern, as has been noted. 

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2 hours ago, Xd the great said:

Why is this such a waste?

Cuz they're throwing away a perfectly good booster. :huh:

 

Tho, according to Reddit via some random guy on twitter, this will actually be the first "long loiter" mission, the upper stage will fire again at apogee to partially circularize the orbit of the GPS sat, not just send it on a transfer orbit.

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4 hours ago, Xd the great said:

Why is this such a waste?

The air force have requested a newly built booster, and demended that it is not recovered... because reasons. 

Let's hope that they were charged far beyond what is reasonable for this, it's so idiotic. 

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3 hours ago, CatastrophicFailure said:

Tho, according to Reddit via some random guy on twitter, this will actually be the first "long loiter" mission, the upper stage will fire again at apogee to partially circularize the orbit of the GPS sat, not just send it on a transfer orbit.

If that's the case, then maybe there IS a good reason for it after all. They'll probably need all the energy they can get.

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8 hours ago, CatastrophicFailure said:

Sigh. Such a waste. ;.;

 

 

7 hours ago, Xd the great said:

Why is this such a waste?

 

5 hours ago, CatastrophicFailure said:

Cuz they're throwing away a perfectly good booster. :huh:

 

Y'all had me panicking for a second, I thought something had gone wrong with the static fire! I kept reading the tweet for double meaning before scrolling down.

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31 minutes ago, Ultimate Steve said:

Y'all had me panicking for a second, I thought something had gone wrong with the static fire! I kept reading the tweet for double meaning before scrolling down.

Same here.

2 hours ago, Lukaszenko said:

If that's the case, then maybe there IS a good reason for it after all. They'll probably need all the energy they can get.

I’m not sure. F9 can get 5.3 tonnes to GTO with landing, and the mass of the GPSIIIA1 is 3880 kg. So I don’t see why the booster had to be thrown away. Of course, the satellite is being taken to MEO, which has higher dv requirements that just GTO, but if you still have a tonne and a half of payload left, can you not get the satellite to the target orbit? The part about using a new booster might make some sense, but unless I underestimate the dv needed to transfer from GTO to MEO, than I don’t see why the booster is being discarded. 

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18 minutes ago, Ozymandias_the_Goat said:

 I’m not sure. F9 can get 5.3 tonnes to GTO with landing, and the mass of the GPSIIIA1 is 3880 kg. So I don’t see why the booster had to be thrown away. Of course, the satellite is being taken to MEO, which has higher dv requirements that just GTO, but if you still have a tonne and a half of payload left, can you not get the satellite to the target orbit? The part about using a new booster might make some sense, but unless I underestimate the dv needed to transfer from GTO to MEO, than I don’t see why the booster is being discarded. 

Assuming a dry mass of 4.5 tons on S2 and an insertion Delta-V of about 1-1.5km/s... For a total of 8.4t dry mass (sat+stage) and a specific impulse of 348s, the second stage would need 4.5 tons of propellant left over to have 1500m/s of Delta-V remaining. That's probably a high estimate as GTO insertion is 1600m/s, but S2 will experience significant boiloff.

4.5t of prop and 3.9 tons of sat is 8.4 tons of MTO payload. F9 can do 5.3t to GTO, and that's a pretty hefty increase if you ask me. Because MEO is lower than GEO it might be able to make it, but I'm guessing it would be really close.

And if it's  *that close* then the mass of S1 recovery hardware would start pushing against the payload capacity. There also may not be enough margin for S2 deorbit. And if an engine fails on ascent that could add to gravity losses.

So if it *can* do it but is really close, I would agree with the decision to go expendable, especially with such an important payload.

 

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1 hour ago, Ultimate Steve said:

So if it *can* do it but is really close, I would agree with the decision to go expendable, especially with such an important payload.

This is what I heard. Even flying expendable, S2 still won’t have enough fuel left over to fully circularize the orbit, but can get it a good chunk of the way there.

If true, this is the kind of flight I would ordinarily expect to go up on a Falcon Heavy (with full recovery), but IIRC it’s not yet fully certified for gummint use, and they’re in a hurry, so... sacrifices... must be made... <_<

 

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Quote

On April 27, 2016, Space Exploration Technologies Corp. (SpaceX), in Hawthorne, California was awarded an $82,700,000 firm-fixed-price contract for launch services to deliver a GPS III satellite to its intended orbit. This launch service contract will include launch vehicle production, mission integration, and launch operations for a GPS III mission. The locations of performance are Hawthorne, California; Cape Canaveral Air Force Station, Florida and McGregor, Texas. The work is expected to be completed by July 31, 2018.

So we know how much SpaceX is being paid for this launch (and the associated mission integration work).

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13 minutes ago, RealKerbal3x said:

So SpaceX has been contracted by the military to launch a satellite so heavy that they won't have the margin to land the booster?

Wouldn't a Falcon Heavy be a better choice for this?

There may or may not be a gap in terms of costs (in time and money) between an expendable single stack, and three brand-new stacks (DoD insists on unused) that would hopefully amortize themselves over subsequent flights.

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2 hours ago, RealKerbal3x said:

So SpaceX has been contracted by the military to launch a satellite so heavy that they won't have the margin to land the booster?

Wouldn't a Falcon Heavy be a better choice for this?

Plus, you know, you don't usually launch high profile payloads on the second flight of a rocket. When at the time of the contract the rocket has not flown at all. And the next FH will be the first Block 5 FH.

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2 hours ago, RealKerbal3x said:

So SpaceX has been contracted by the military to launch a satellite so heavy that they won't have the margin to land the booster?

Wouldn't a Falcon Heavy be a better choice for this?

It’s not that it’s heavy, it’s less than 4000kgs, but they’re going to partially circularize the orbit with the upper stage, and that needs a lot more fuel. Falcon Heavy (still) is not yet certified for gov’t launches and won’t be until at least the STP-2 flight later next year. 

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3 hours ago, CatastrophicFailure said:

It’s not that it’s heavy, it’s less than 4000kgs, but they’re going to partially circularize the orbit with the upper stage, and that needs a lot more fuel. Falcon Heavy (still) is not yet certified for gov’t launches and won’t be until at least the STP-2 flight later next year. 

One weakness with falcon 9 in this mission profile is that its only two stages with an large and heavy upper stage, most rockets are 2.5 stages with an smaller upper stage. This has little impact then sending something heavy to LEO but it hurt falcon 9 then needing to do lots of dV on something light as the upper stage dry mass might out mass the payload. Look at LEO versus GTO stats for falcon 9 and 2.5 stage rockets. 
An small kick stage for falcon 9 makes some sense 

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11 hours ago, magnemoe said:

One weakness with falcon 9 in this mission profile is that its only two stages with an large and heavy upper stage, most rockets are 2.5 stages with an smaller upper stage. This has little impact then sending something heavy to LEO but it hurt falcon 9 then needing to do lots of dV on something light as the upper stage dry mass might out mass the payload. Look at LEO versus GTO stats for falcon 9 and 2.5 stage rockets. 
An small kick stage for falcon 9 makes some sense 

Isn’t that rather typical for US launchers thanks to the Centaur? As opposed to current Soviet :wink: launchers, all of which are effectively four-stage?

And what’s the problem with slapping one of those Star solid-fuel kick stages onto the sat?

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