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SpaceX Discussion Thread

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9 minutes ago, Scotius said:

If only our digestive tract could handle such diet, we could live on milk and potatoes indefinitely.

Are you saying my diet of only cheesy fries isn't good for me?

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1 hour ago, Scotius said:

Got milk?

latest?cb=20150226075447

I'm serious. If only our digestive tract could handle such diet, we could live on milk and potatoes indefinitely.

Not sure that would work on Mars. Might find better success on the Moon.

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6 hours ago, Jaelommiss said:

Not sure that would work on Mars.

It works, don't you see on the photo?
Actually these are goats, but thanks to the low atmospheric pressure, on Mars they've inflated in cows.

 

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7 hours ago, Scotius said:

If only our digestive tract could handle such diet, we could live on milk and potatoes indefinitely.

Why not?
1156f4ec-29c8-4cd9-80db-7d4ee330b1d0.jpg

 

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It's been a long time since there has been any falcon 9 launch and it doesn't look like there is going to be another one soon. Why is that? Because a couple of months ago spacex did so many launches back to back i couldn't keep up.

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7 minutes ago, Flying dutchman said:

It's been a long time since there has been any falcon 9 launch and it doesn't look like there is going to be another one soon. Why is that? Because a couple of months ago spacex did so many launches back to back i couldn't keep up.

They’ve run out of things to launch ATM. 

They’re ready, customers aren’t. And Starlink is targeted late next month. 

Hang on, digging up article...

Ok, boom.

But fret not, next year there could be as many as 24 Starlink launches (maybe 4 this year still) on top of all the other customer launches. :o

Back to that lovely two-week cadence!

hopefully. :unsure:

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2 hours ago, CatastrophicFailure said:

They’ve run out of things to launch ATM

More carry-out boxes than food? That must be frustrating. 

“Come on, guys! Build your satellites faster! We’ve got a schedule to maintain!”

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12 hours ago, Scotius said:

Got milk?

latest?cb=20150226075447

I'm serious. If only our digestive tract could handle such diet, we could live on milk and potatoes indefinitely.

The greatest mystery... and possibly a source of anti entropy and free energy... WHERE DO THE COWS GET THE CALCIUM!!! They are not magic matter producers are they? ;)

 

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1 hour ago, Technical Ben said:

The greatest mystery... and possibly a source of anti entropy and free energy... WHERE DO THE COWS GET THE CALCIUM!!! They are not magic matter producers are they? ;)

They are fusion reactors that produce calcium.

2 hours ago, GearsNSuch said:

More carry-out boxes than food? That must be frustrating. 

“Come on, guys! Build your satellites faster! We’ve got a schedule to maintain!”

Seems like a good time for SpaceX employees to go on holidays.

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6 hours ago, Flying dutchman said:

It's been a long time since there has been any falcon 9 launch and it doesn't look like there is going to be another one soon. Why is that? Because a couple of months ago spacex did so many launches back to back i couldn't keep up.

Supposedly a few Starlink launches might happen starting in October.

In November there's JCSAT 18/Kacific 1(no date)

In December there is CRS19 to the Station, and we're still waiting on the max Q abort test.

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3 hours ago, Xd the great said:

Seems like a good time for SpaceX employees to go on holidays.

Well they have been building 3 huge prototypes...

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ULA chief’s opinion on reusability is surprisingly similar to Rogozin’s explanation of why Roscosmos isn’t very interested in reusable rockets...

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18 minutes ago, sh1pman said:

ULA chief’s opinion on reusability is surprisingly similar to Rogozin’s explanation of why Roscosmos isn’t very interested in reusable rockets...

That's a reasonable take, except that historically ULA has been at the pork trough.

 

11 minutes ago, Barzon Kerman said:

imagine talking sh#t about Tory... :mad:

Well, he wasn't really being rude to Tory (who I really like). I think he answers the question reasonably, too.

This is not directly related, but many talk about waiting to see prices drop, and the recent SpaceX monthly smallsat rideshare program is exactly a huge price reduction. It has every chance of simply wrecking the small rocket companies, frankly, it's much cheaper than dedicated smallsat launch (RocketLab moving to reuse is likely related).

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I would like to see the analysis behind that claim. On the surface, one might think that even a single re-use must save money, but I'm sure it depends a lot on how expensive it is to design parts to be re-used, to do refurbishments, to have a barge and a landing pad, to add landing legs, to reserve fuel for landing (especially including all the fuel needed to lift the landing fuel instead of the payload)....

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35 minutes ago, mikegarrison said:

I would like to see the analysis behind that claim. On the surface, one might think that even a single re-use must save money, but I'm sure it depends a lot on how expensive it is to design parts to be re-used, to do refurbishments, to have a barge and a landing pad, to add landing legs, to reserve fuel for landing (especially including all the fuel needed to lift the landing fuel instead of the payload)....

Propellant costs are not that big a deal, I want to say a couple hundred grand, total. So the reserved props cost effectively nothing.

Barge, legs, etc? Some real cost, as well as any refurb.

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1 hour ago, Barzon Kerman said:

imagine talking sh#t about Tory... :mad:

Were you referring to me or to the person who asked him about reuse?

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8 minutes ago, sh1pman said:

Were you referring to me or to the person who asked him about reuse?

Musta been about the tweet.

7 hours ago, tater said:

In November there's JCSAT 18/Kacific 1(no date)

SpaceX filed paperwork for this one, it's set to NET November 11 as of today.

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2 hours ago, sh1pman said:

Tory's arguing that the total costs of a flyback, refurbishment, and reuse program, over time, offset 90% of the value of a booster.

Even adjusting for opportunity cost, propellant margins, and a dozen other possible elements, I don't see how that's remotely possible.

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I don't know where people get this idea, but propellant costs are not completely negligible. Everything costs money.

Furthermore, as with all flight vehicles, propellant capacity has knock-on costs. More propellant mass means more structural mass which in turn means still more propellant. Likewise, more propellant mass means more thrust is required which means bigger/heavier/more engines which means -- guess what? -- still more propellant mass, etc.

Landing legs, restart capability, re-entry control surfaces -- they all add mass too. And so they all require more propellant, more thrust, more structure, meaning still more propellant, etc.

This vicious weight loop is absolutely fundamental to flight vehicle design.

My guess is that the payload mass fraction of a Falcon 9 is significantly lower than some of the competitor rockets. It would be interesting to see the real data on that.

Edited by mikegarrison

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54 minutes ago, mikegarrison said:

I don't know where people get this idea, but propellant costs are not completely negligible. Everything costs money.

Furthermore, as with all flight vehicles, propellant capacity has knock-on costs. More propellant mass means more structural mass which in turn means still more propellant. Likewise, more propellant mass means more thrust is required which means bigger/heavier/more engines which means -- guess what? -- still more propellant mass, etc.

Landing legs, restart capability, re-entry control surfaces -- they all add mass too. And so they all require more propellant, more thrust, more structure, meaning still more propellant, etc.

Someone priced out the RP-1 and LOX on reddit a while ago and came up with a number under $200,000 for the propellants, that's where I got the number. It might be low, I just checked on nasaspaceflight, and they have RP-1 at around >$5/kg, which makes the props cost several hundred thousand (closer to a million than 200k), not a couple. It's real money, but the reserve props are not huge costs in the scheme of things.

Quote

This vicious weight loop is absolutely fundamental to flight vehicle design.

My guess is that the payload mass fraction of a Falcon 9 is significantly lower than some of the competitor rockets. It would be interesting to see the real data on that.

F9 performance has improved so much that they have loads of margin. Payload mass fraction of F9 is 4.1% (expended).

Musk said that RTLS was a 40% payload hit, so that's a payload mass fraction of 2.5%, and he said that it's an 18% hit for ASDS landing, which would give the payload mass fraction of 3.4% (pretty respectable, that's almost Atlas V).

 

 

Edited by tater

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2 hours ago, mikegarrison said:

This vicious weight loop is absolutely fundamental to flight vehicle design.

My guess is that the payload mass fraction of a Falcon 9 is significantly lower than some of the competitor rockets. It would be interesting to see the real data on that.

The genius of Falcon 9 was the Merlin engine. It has such a tremendously great thrust to weight ratio that they were able to uprate and uprate and uprate it and so kept gaining margin without adding significant dry mass, to the point that they can reserve props and still throw ANYTHING on commercial markets.

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6 minutes ago, sevenperforce said:

The genius of Falcon 9 was the Merlin engine. It has such a tremendously great thrust to weight ratio that they were able to uprate and uprate and uprate it and so kept gaining margin without adding significant dry mass, to the point that they can reserve props and still throw ANYTHING on commercial markets.

And they evolved the engine so much it doubled in thrust. Not to mention that they used super-chill propellants, making the rocket able to hold more fuel and get more thrust.

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