Author Topic: General Falcon and Dragon discussion (Thread 14)  (Read 469633 times)

Offline edkyle99

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #240 on: 03/20/2017 01:30 pm »
Quick question.  On their webpage SX states F9 can carry 22,800 kg to LEO, however in their user guide they also state that the heavy PAF can only support up to 10,886 kg. My question would be: Can the F9 really carry 22mT into orbit? Or there would be some structural limitation that prevents it?
The payload to LEO is mostly a yardstick to compare performance of different rockets. Its a mostly notional number
I think that's a 200Km LEO orbit.
Typical launches to LEO (except for ISS) are to 500Km and higher orbits, that would eat a few tons off that figure.
Add margins for ASDS recovery (which doubles as a safety margin for engine off), and the realistic figure would be 17 tons or less.
If a customer approached SX with the requirement for even 20 tons to 200Km LEO orbit , they would be offered a FH launch instead.
200Km orbits are unstable with just enough atmospheric drag to re-enter within a few years.
Another way to look at capability is to see what Falcon 9 has actually lifted.  So far, max payload to LEO x 51.6 deg has been somewhere around 9.3 tonnes, maybe (SpaceX doesn't announce Dragon liftoff mass so this is based on cargo plus dated Dragon information from SpaceX).  This was with first stage recovery downrange.  In addition, we've just seen an expendable Falcon 9 boost 5,600 kg (or so) to GTO.

 - Ed Kyle
« Last Edit: 03/20/2017 01:33 pm by edkyle99 »

Online envy887

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #241 on: 03/20/2017 03:37 pm »
Quick question.  On their webpage SX states F9 can carry 22,800 kg to LEO, however in their user guide they also state that the heavy PAF can only support up to 10,886 kg. My question would be: Can the F9 really carry 22mT into orbit? Or there would be some structural limitation that prevents it?
The payload to LEO is mostly a yardstick to compare performance of different rockets. Its a mostly notional number
I think that's a 200Km LEO orbit.
Typical launches to LEO (except for ISS) are to 500Km and higher orbits, that would eat a few tons off that figure.
Add margins for ASDS recovery (which doubles as a safety margin for engine off), and the realistic figure would be 17 tons or less.
If a customer approached SX with the requirement for even 20 tons to 200Km LEO orbit , they would be offered a FH launch instead.
200Km orbits are unstable with just enough atmospheric drag to re-enter within a few years.
Another way to look at capability is to see what Falcon 9 has actually lifted.  So far, max payload to LEO x 51.6 deg has been somewhere around 9.3 tonnes, maybe (SpaceX doesn't announce Dragon liftoff mass so this is based on cargo plus dated Dragon information from SpaceX).  This was with first stage recovery downrange.  In addition, we've just seen an expendable Falcon 9 boost 5,600 kg (or so) to GTO.

 - Ed Kyle

Iridium was 9,600 kg to 625 km polar LEO with downrange landing. Much higher performance than Dragon to ISS.

Offline Roy_H

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #242 on: 03/20/2017 04:02 pm »
Another way to look at capability is to see what Falcon 9 has actually lifted.  So far, max payload to LEO x 51.6 deg has been somewhere around 9.3 tonnes, maybe (SpaceX doesn't announce Dragon liftoff mass so this is based on cargo plus dated Dragon information from SpaceX).  This was with first stage recovery downrange.  In addition, we've just seen an expendable Falcon 9 boost 5,600 kg (or so) to GTO.

 - Ed Kyle
5,600kg to GTO is a lot lower than their advertised 8,300kg.  And I was under the (false) impression that the advertised payloads were with recovered booster. something is definitely amiss here. If they could truly put 8,300kg into GTO expendable then I really doubt they would have had to remove the legs etc for 5.600kg. Am I correct in that they are not chilling the LOX as much as originally planned, and could there be THAT much difference for just colder LOX?
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Offline whitelancer64

Re: General Falcon and Dragon discussion (Thread 14)
« Reply #243 on: 03/20/2017 04:08 pm »
Another way to look at capability is to see what Falcon 9 has actually lifted.  So far, max payload to LEO x 51.6 deg has been somewhere around 9.3 tonnes, maybe (SpaceX doesn't announce Dragon liftoff mass so this is based on cargo plus dated Dragon information from SpaceX).  This was with first stage recovery downrange.  In addition, we've just seen an expendable Falcon 9 boost 5,600 kg (or so) to GTO.

 - Ed Kyle
5,600kg to GTO is a lot lower than their advertised 8,300kg.  And I was under the (false) impression that the advertised payloads were with recovered booster. something is definitely amiss here. If they could truly put 8,300kg into GTO expendable then I really doubt they would have had to remove the legs etc for 5.600kg. Am I correct in that they are not chilling the LOX as much as originally planned, and could there be THAT much difference for just colder LOX?

The numbers on the SpaceX website are for expendable flights.

The payload penalty for reuse is something like 33-40%

*edit* Citation: Elon Musk on Twitter, 30 April 2016

"Max performance numbers are for expendable launches. Subtract 30% to 40% for reusable booster payload."

https://twitter.com/elonmusk/status/726559990480150528
« Last Edit: 03/20/2017 04:14 pm by whitelancer64 »
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Offline old_sellsword

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #244 on: 03/20/2017 04:11 pm »
Another way to look at capability is to see what Falcon 9 has actually lifted.  So far, max payload to LEO x 51.6 deg has been somewhere around 9.3 tonnes, maybe (SpaceX doesn't announce Dragon liftoff mass so this is based on cargo plus dated Dragon information from SpaceX).  This was with first stage recovery downrange.  In addition, we've just seen an expendable Falcon 9 boost 5,600 kg (or so) to GTO.

 - Ed Kyle
5,600kg to GTO is a lot lower than their advertised 8,300kg.  And I was under the (false) impression that the advertised payloads were with recovered booster. something is definitely amiss here. If they could truly put 8,300kg into GTO expendable then I really doubt they would have had to remove the legs etc for 5.600kg. Am I correct in that they are not chilling the LOX as much as originally planned, and could there be THAT much difference for just colder LOX?

They probably didn't have to remove the legs and fins for EchoStar 23, but did anyways because it's a waste to throw them away and they had the time to remove them.

Online envy887

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #245 on: 03/20/2017 04:16 pm »
Another way to look at capability is to see what Falcon 9 has actually lifted.  So far, max payload to LEO x 51.6 deg has been somewhere around 9.3 tonnes, maybe (SpaceX doesn't announce Dragon liftoff mass so this is based on cargo plus dated Dragon information from SpaceX).  This was with first stage recovery downrange.  In addition, we've just seen an expendable Falcon 9 boost 5,600 kg (or so) to GTO.

 - Ed Kyle
5,600kg to GTO is a lot lower than their advertised 8,300kg.  And I was under the (false) impression that the advertised payloads were with recovered booster. something is definitely amiss here. If they could truly put 8,300kg into GTO expendable then I really doubt they would have had to remove the legs etc for 5.600kg. Am I correct in that they are not chilling the LOX as much as originally planned, and could there be THAT much difference for just colder LOX?

8,300 kg to GTO is fully expendable, and presumably with Block 5 performance upgrades which are not yet flying.

SpaceX's listed price is $62M for 5,500 kg to GTO which presumably give a chance to recover the booster. The heaviest payload flown with a booster recovery attempt was ~5,300 kg to GTO.

If you're wondering why they take the legs off, go price out 2,000 kg of aerospace grade carbon fiber composites sometime...

Offline baldusi

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #246 on: 03/20/2017 04:49 pm »
Please remember that not all GTO are equal. The rest of the world uses 1,500m/s deficit GTO. The Americans usually quote 1,804m/s GTO, which is not plane change from the Cape. The EchoStar 23 did something in the middle. And again, an Ariane 5 or Zenit-3SLB leave the payload at the correct apogee and with practically no plane change. Proton-M, H-IIA and Long March 3 leave you with a certain plane change requirement.
SpaceX generally uses a supersynchronous GTO for lower deficit that requires more careful maneuvering. Still cheap for the service, but please consider all those factors when comparing.

Offline abaddon

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #247 on: 03/20/2017 07:21 pm »
That is all true, but it is not strictly a property of the rocket that it happens to be launched from an equitorial launch site, it is a property of the organization and their geographic location.  It is inarguably a property of the service that is performed, of course, and when considering price (not strictly capability) of the service.

The distinction is usually without a difference, but sometimes it is meaningful; for example a Soyuz launched from Kourou suddenly becomes more capable than before.  In this case it seems unlikely Falcon 9 will ever launch from somewhere significantly closer to the equator...
« Last Edit: 03/20/2017 07:48 pm by abaddon »

Offline edkyle99

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #248 on: 03/20/2017 08:29 pm »
Iridium was 9,600 kg to 625 km polar LEO with downrange landing. Much higher performance than Dragon to ISS.
I have that as 8,600 kg (ten 860 kg satellites) to 610 x 620 km x 86.4 deg.

Pardon me if I'm repeating someone else, but the SpaceX web site numbers are for fully expendable Block 5, which hasn't begun flying to date.  The current v1.2 (Block 3) variant presumably has less capability.

 - Ed Kyle
« Last Edit: 03/20/2017 08:32 pm by edkyle99 »

Offline whitelancer64

Re: General Falcon and Dragon discussion (Thread 14)
« Reply #249 on: 03/20/2017 08:35 pm »
Iridium was 9,600 kg to 625 km polar LEO with downrange landing. Much higher performance than Dragon to ISS.
I have that as 8,600 kg (ten 860 kg satellites) to 610 x 620 km x 86.4 deg.

Pardon me if I'm repeating someone else, but the SpaceX web site numbers are for fully expendable Block 5, which hasn't begun flying to date.  The current v1.2 (Block 3) variant presumably has less capability.

 - Ed Kyle

plus the 1,000-kg satellite dispenser.
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Offline edkyle99

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #250 on: 03/21/2017 12:02 am »
Iridium was 9,600 kg to 625 km polar LEO with downrange landing. Much higher performance than Dragon to ISS.
I have that as 8,600 kg (ten 860 kg satellites) to 610 x 620 km x 86.4 deg.

Pardon me if I'm repeating someone else, but the SpaceX web site numbers are for fully expendable Block 5, which hasn't begun flying to date.  The current v1.2 (Block 3) variant presumably has less capability.

 - Ed Kyle

plus the 1,000-kg satellite dispenser.
This, or some of this, might represent potential payload mass on future, single-satellite missions, but it was non-revenue on this flight - like the seats on an airplane that hold the paying customers, little different from the usual payload attach fitting and as far as the rocket equation is concerned the same as upper stage burnout mass.

 - Ed Kyle
« Last Edit: 03/21/2017 12:02 am by edkyle99 »

Offline Comga

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #251 on: 03/21/2017 12:09 am »
http://spacenews.com/china-studying-reusable-rockets-similar-to-spacex/[/size]


"Chinese researchers said they looked into making a powered landing of the first stage, as SpaceX does with the Falcon 9, but concluded it was 'extremely difficult' and inefficient.
A concept being developed would use parachutes to slow down first stages after separation, then deploy an airbag to cushion the stage’s landing on dry land. "

http://www.scmp.com/news/china/policies-politics/article/2079822/china-developing-system-recover-reuse-parts-space

"multiple censors [sic] and a flight control system guide the descent"
English is a tough language but "multiple censors" in China is an amusing mistake.
The animation shows them recovering the ground-lit solid rockets.
Parachutes and airbags....

So what SpaceX has done is judged to be too difficult for the Chinese with their tens of thousands of people working on the problem. 
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Online envy887

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #252 on: 03/21/2017 12:16 am »
Iridium was 9,600 kg to 625 km polar LEO with downrange landing. Much higher performance than Dragon to ISS.
I have that as 8,600 kg (ten 860 kg satellites) to 610 x 620 km x 86.4 deg.

Pardon me if I'm repeating someone else, but the SpaceX web site numbers are for fully expendable Block 5, which hasn't begun flying to date.  The current v1.2 (Block 3) variant presumably has less capability.

 - Ed Kyle

plus the 1,000-kg satellite dispenser.
This, or some of this, might represent potential payload mass on future, single-satellite missions, but it was non-revenue on this flight - like the seats on an airplane that hold the paying customers, little different from the usual payload attach fitting and as far as the rocket equation is concerned the same as upper stage burnout mass.

 - Ed Kyle
Doesn't the dispenser go above the PAF?

Offline Robotbeat

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #253 on: 03/21/2017 12:55 am »
http://spacenews.com/china-studying-reusable-rockets-similar-to-spacex/[/size]


"Chinese researchers said they looked into making a powered landing of the first stage, as SpaceX does with the Falcon 9, but concluded it was 'extremely difficult' and inefficient.
A concept being developed would use parachutes to slow down first stages after separation, then deploy an airbag to cushion the stage’s landing on dry land. "

http://www.scmp.com/news/china/policies-politics/article/2079822/china-developing-system-recover-reuse-parts-space

"multiple censors [sic] and a flight control system guide the descent"
English is a tough language but "multiple censors" in China is an amusing mistake.
The animation shows them recovering the ground-lit solid rockets.
Parachutes and airbags....

So what SpaceX has done is judged to be too difficult for the Chinese with their tens of thousands of people working on the problem.
If China builds their stages similar to Russia (i.e.: like a tank), this makes sense. It takes very good mass fraction to do what SpaceX does.
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Offline CuddlyRocket

Re: General Falcon and Dragon discussion (Thread 14)
« Reply #254 on: 03/21/2017 02:17 am »
http://spacenews.com/china-studying-reusable-rockets-similar-to-spacex/[/size]

"Chinese researchers said they looked into making a powered landing of the first stage, as SpaceX does with the Falcon 9, but concluded it was 'extremely difficult' and inefficient.

But demonstrated to be possible.

Quote
A concept being developed would use parachutes to slow down first stages after separation, then deploy an airbag to cushion the stage’s landing on dry land. "

Which has not been demonstrated to be possible. In fact, didn't SpaceX try something similar with parachutes, but couldn't make it work?

Possibly a bit of not-invented-here syndrome going on!

Offline AncientU

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #255 on: 03/21/2017 09:08 am »
Chutes can't slow it until there's an atmosphere... too late per SpaceX.
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Offline bdub217

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #256 on: 03/21/2017 10:52 am »
Forgive me if this has been discussed before. Why did SpaceX leave their Kwajalein Atoll launch site? I know it's remote (guess they don't make them any more remote) but the advantage of a near equator launch site, no range conflicts, and a lack of traffic and lookey loos would seem to be a clear advantage.

Offline cscott

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #257 on: 03/21/2017 11:12 am »
Logistical challenges. In particular they had to build their own LOX plant on the island, and it had trouble keeping up with long launch campaigns, even for Falcon 1.  The LOX would boil off and they had to wait days to make enough for another attempt.  When they tried to bring the LOX in by boat, most of it boiled off in transit.

Imagine taking all the work they are doing to the pad at LC40 and inserting transportation to to the middle of the Pacific for every worker, nut, and bolt.
« Last Edit: 03/21/2017 11:13 am by cscott »

Offline abaddon

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #258 on: 03/21/2017 12:54 pm »
This, or some of this, might represent potential payload mass on future, single-satellite missions
Exactly.  We're trying to determine capability here, aren't we?

Offline abaddon

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Re: General Falcon and Dragon discussion (Thread 14)
« Reply #259 on: 03/21/2017 01:03 pm »
Forgive me if this has been discussed before. Why did SpaceX leave their Kwajalein Atoll launch site? I know it's remote (guess they don't make them any more remote) but the advantage of a near equator launch site, no range conflicts, and a lack of traffic and lookey loos would seem to be a clear advantage.
As cscott says, way more disadvantages than advantages, although as late as 2010 it was still listed as a launch site option for Falcon 9.

Originally the Falcon 1 was supposed to launch from Vandenberg, but overflight restrictions on their pad were inhibiting their ability to launch, see   https://en.wikipedia.org/wiki/SpaceX_launch_facilities#Two_launch_pads_for_Falcon_1.

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