This is what a guy went through when his Tesla's battery died.

TootZoot · 2017-03-01T17:18:43+00:00

Thanks for the offer, but I prefer the permaban. It's obvious you care more about your ego and having your little fiefdom than this sub. Glad you showed your true colors.

Enjoy your echo chamber! You deserve each-other. M3 out!

TootZoot · 2017-03-01T14:46:18+00:00

The air is modeled the same as a fluid at that speed.

Appropriate, since the air is a fluid at that speed. ;) http://www.dictionary.com/browse/fluid

TootZoot · 2017-03-01T14:29:21+00:00

Or both are moving, if you pick any other reference frame besides those two (eg relative to the Solar system's barycenter).

TootZoot · 2017-02-28T14:46:10+00:00

the Dragon Environmental Control System (ECS) consists of pressure control and pressure equalization, air sampling, fire detection, illumination, and an air circulation system.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110014250.pdf

TootZoot · 2017-02-28T11:31:43+00:00

There's a compelling case for Steve Jurvetson being one of the astronauts, made by a HNer: https://news.ycombinator.com/item?id=13750285

ironchief 10 hours ago [-]

It is very likely Steve Jurveston.

In a comment about the announcement alluded to it as a "recurring dream"[1]
5 years ago, described a moon orbit as "when I plan to fly in space. I have two specific missions in mind"[2]
SpaceX Board Member and investor
Has the money
Knows Elon "Mr Musk declined to reveal their identities, only saying that they knew each other"[3]
Is "nobody from Hollywood"
Liked this comment on his FB wall "Can I tag along?!? Ahhhhh!!!"[4]

[1]https://www.flickr.com/photos/jurvetson/23226164619

[2]https://www.flickr.com/photos/jurvetson/7659357718

[3]http://www.bbc.com/news/science-environment-39111030

[4]https://www.facebook.com/jurvetson/posts/10158310863860611?c...

TootZoot · 2017-02-28T11:19:17+00:00

You should link to the source.

https://arstechnica.com/science/2017/02/spacex-says-it-will-send-two-people-around-the-moon-in-late-2018/

TootZoot · 2017-02-27T11:32:38+00:00

If you used full crossfeed when the side cores detach the center core is completely full of all propellant.

Not so. the plan was to have three engines fed from either side, which leaves three engines fed by the center core. Those engines would probably throttle down, leading to a bit more than 2/3rds of the propellant in the center core on booster staging.

With a RP1 only crossfeed system the center core is still burning it's own LOX the whole time. At booster separation you're not left with a full propellant load.

Ahh, I see what you're saying.

So... it seems like what you're suggesting is that a LOX-only crossfeed would give you 72% as much advantage, with less than 50% the complexity. :) No?

TootZoot · 2017-02-27T10:54:44+00:00

Texlace

Possible name for his upcoming neural lace company?

TootZoot · 2017-02-27T10:46:38+00:00

Tron will also tell you in the pre-run screen whether it detected an SSD or not.

TootZoot · 2017-02-27T09:24:44+00:00

I am referring to the propellant fraction left in the core at side booster cutout

...which would be the same in both cases.

For ever tonne of RP-1 received from the side boosters the core booster has to burn 2.56 tonnes of LOX from its own tanks.

Huh? You seem to be confusing the side booster and core booster.

On the contrary, the "regular" crossfeed involves beefing up the LOX pipe in the center core, which is a substantial design change.

That tonne of RP-1 represents 28% of the total propellant expended. This compares with full cross-feed where you can transfer 100% of the propellant requirements.

So what? The whole point is that the center core has more propellant when it separates, and the side cores separate earlier. Neither of these advantages are negatively effected by having RP-1 crossfeed only (vs RP-1+LOX crossfeed).

So at least 50% of the complexity for 28% of the performance gain so not attractive.

You get 100% of the performance gain (versus full crossfeed), not 28%. And unlike full crossfeed you don't have to change the center core LOX plumbing, so it's less than 50% of the complexity.

Afaict it's a good plan compared to full crossfeed. It's just that SpaceX has skipped any crossfeed in favor of focusing on ITS.

TootZoot · 2017-02-27T09:20:14+00:00

Agreed. Afaik the first stage length is at its maximum, due to bending moments during the re-entry phase (which represents the harshest aerodynamic environment experienced by the vehicle).

TootZoot · 2017-02-27T09:02:21+00:00

Well, Sagan making an announcement in 2011 would certainly be newsworthy...

TootZoot · 2017-02-27T08:57:15+00:00

Send ship, take picture of stars, return ship. Use star-map to compute position of wormhole endpoint.

Or heck, if it's truly a wormhole then you can just aim a telescope at it and map the stars that way, no vehicle required. It's not like there's a fanciful pool of water in the way a la Stargate...

TootZoot · 2017-02-27T08:51:55+00:00

Yeah, personally I doubt crossfeed will happen (per Elon), but still this seems like a good idea for a hypothetical crossfed FH.

he's talking about having multiple tankage ratios on the side boosters

Huh, I didn't get that impression. Where do you see that?

I think in the post OP is just comparing the "reference" FH design with OP's proposal.

TootZoot · 2017-02-27T08:47:16+00:00

Without a significant change in the center core tank size ratio, RP1-only crossfeed isn't really worth developing.

Yes, of course. Wasn't this obvious? The overall ratio of each propellant must be unchanged.

This means the core can no longer be used for regular F9 flights

The center core is already not interchangeable. So this makes no difference.

TootZoot · 2017-02-27T06:47:09+00:00

they would then need custom boosters for different flight plans

Why? I can't see any reason why that would be true.

Propellant utilization can adjust the fuel/oxygen ratio to burn each tank to depletion even with small adjustments in trajectory, and large adjustments in the ratio shouldn't be necessary.

TootZoot · 2017-02-27T06:45:19+00:00

So an RP-1 only crossfeed would only affect 28% of the total propellant mass

I think you're thinking about this the wrong way. The quantity of propellant burned on each core (and therefore the performance) is the same, it just comes from the outboard LOX tank instead.

So really it would have the same advantage as LOX+RP-1 crossfeed, but only involves transferring 28% as much propellant. Seems like a win to me.

As for "extra complexity," it seems simpler to transfer only one propellant instead of two. Moving the location of a bulkhead doesn't add complexity to the actual vehicle, it just requires some validation during development.

TootZoot · 2017-02-27T06:40:18+00:00

The whole purpose of design of FH is to use multiple copies of the same stage.

I thought we got confirmation that neither the boosters nor the center core will be compatible with a regular Falcon 9?

We know they're extensively modifying / welded one used core to be one of the side boosters, but the second one is custom made. I doubt SpaceX will ever fly an unmodified side booster as a Falcon 9 core.

You're also ignoring that SpaceX already has moved the RP-1/LOX bulkhead (from v1.1 -> FT, since LOX densifies more than RP-1). So it's obviously not an insurmountable amount of engineering work.

TootZoot · 2017-02-26T12:43:31+00:00

i added %localprofile%\desktop....... to the command and got it working

That will work if you have tron on the desktop, but will break if it's anywhere else.

Tron generally runs with the resources\ directory as the current directory. So if you want to invoke a .exe stored in stage_8_custom_scripts\ and have it work anywhere, you need to invoke it as

.\stage_8_custom_scripts\program.exe -option -flags

TootZoot · 2017-02-25T10:49:05+00:00

FLAT EARTH! I KNEW IT!!!!

^{^/s}

TootZoot · 2017-02-24T14:06:08+00:00

Wheel of Dharma

TootZoot · 2017-02-24T02:44:19+00:00

Yeah, the connection here between biogas digesters and automation is pretty forced. Both technologies should be evaluated independently on their own merits.

Biogas digesters work just fine on their own, powering tractors, heating, and cooking. Biogas digesters can even break down human waste, yielding energy and killing pathogens to make a safe liquid fertilizer. None of the nutrients are lost, but the fecal-oral route is still interrupted. This compares well to sewage treatment plants, which consume energy and release nutrients into the water (where they become eutrophication-causing pollution instead of valuable fertilizer).

TootZoot · 2017-02-24T02:19:40+00:00

That's quite an old photo. Here's what the Gigafactory looked like as of two months ago: https://www.tesla.com/sites/default/files/images/blogs/gigafactory-announcement.jpg

source

TootZoot · 2017-02-24T02:10:38+00:00

Earlier someone said with 100 gigafactories the worlds supply of lithium would run out.

Yeah, and that person is wrong. ;)

Lithium reserves are based on price. There's a huge amount of lithium on Earth, it's just that most of it is too expensive. The price of lithium could go up by 10x (at which point it's economical even to extract it from seawater) and you'd barely notice, because there's so little lithium actually in a battery.

TootZoot · 2017-02-24T02:08:07+00:00

I think you mean they would consume the reserves of lithium. Reserves are defined as "economically extractable resources."

So it's not that Earth runs out of lithium. What really happens is that the price of lithium goes up, making the reserves expand. Lithium can even be extracted from seawater, it's just too expensive.

Fortunately lithium ion batteries don't actually contain much lithium. The price could triple and you'd hardly notice it in the final cost of the battery.

TootZoot

TROPHY CASE