SpaceX News

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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happyjack27
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Re: SpaceX News

Postby happyjack27 » Fri Sep 30, 2016 5:41 pm


happyjack27
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Re: SpaceX News

Postby happyjack27 » Fri Sep 30, 2016 7:08 pm

maybe creating a solar furnace, or multiple, might be a good early step for bootstrapping. since i imagine most of the energy use in materials production would be for heating.

better conversion efficiency if you don't convert it at all.

and much easier to make mirrors (very thin layer of aluminum or silicon-carbide) than photo-voltaics.

and lets be clear - there is no wood on mars.

krenshala
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Re: SpaceX News

Postby krenshala » Fri Sep 30, 2016 8:52 pm


happyjack27
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Re: SpaceX News

Postby happyjack27 » Fri Sep 30, 2016 9:26 pm


happyjack27
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Re: SpaceX News

Postby happyjack27 » Fri Sep 30, 2016 9:54 pm

I goofed that - for moon to GTO refueling, you only have to carry the payload for half the trip.

So presuming the payload is the bulk of the dry mass, it's more like 3x the deliverable mass per trip. So you'd only need 1 trip to refuel a SpaceX interplanetary.

That's assuming you can somehow get a booster stage on there, (which doesn't need nearly as much thrust, and should e optimized vacu rather than sea level.)

happyjack27
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Re: SpaceX News

Postby happyjack27 » Fri Sep 30, 2016 10:23 pm

:oops: Seeing as though you needn't contend with atmosphere, you might as well make your moon-based refueler looked like Armadillo aerospace's "pixel" - four spherical tanks and a rocket. Thus minimizing it's dry mass.

Still could probably benefit from two stages - with the fuel mass and thrust ratios choosen intelligently.

happyjack27
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Re: SpaceX News

Postby happyjack27 » Fri Sep 30, 2016 11:38 pm

And regarding the rocket equation and Elon's claim that multiple launches are more efficient:

Imagine two IPS's, stapled together. Now their fuel cost would be double and their payload delivery would be double.

Now let's say instead of stapling them together you launch them separately. This saves a substantial amount on zinc and iron. But apart from that, it's about the same.

So I wonder how this reasoning fits in with the rocket equation.

Well the rocket equation is really based on the ratio of total mass to dry mass.

You double both, and you keep that ratio the same. And thus you keep the delta-v the same.

Maui
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Re: SpaceX News

Postby Maui » Sat Oct 01, 2016 1:44 am

Paging Delta:

"As part of the investigation, SpaceX officials had come across something suspicious they wanted to check out, according to three industry officials with knowledge of the episode. SpaceX had still images from video that appeared to show an odd shadow, then a white spot on the roof of a nearby building belonging to ULA, a joint venture between Lockheed Martin and Boeing."

Diogenes
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Re: SpaceX News

Postby Diogenes » Sat Oct 01, 2016 1:51 pm

‘What all the wise men promised has not happened, and what all the damned fools said would happen has come to pass.’
— Lord Melbourne —

Aero
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Re: SpaceX News

Postby Aero » Sat Oct 01, 2016 5:59 pm

I see the grid fins but where are the landing legs?
Aero

Giorgio
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Re: SpaceX News

Postby Giorgio » Sat Oct 01, 2016 6:46 pm

A society of dogmas is a dead society.

happyjack27
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Re: SpaceX News

Postby happyjack27 » Sat Oct 01, 2016 7:15 pm

using numbers from wikipedia (right side): https://en.wikipedia.org/wiki/ITS_launc ... ing_launch

i calculated deltav for various configurations: https://docs.google.com/spreadsheets/d/ ... sp=sharing

using 9.4 as the deltav needed to reach LEO, a few discoveries:

* all 3 ships - booster, tanker, and transport (with no cargo), can reach LEO by themselves. (assuming no payload)
* a transport with no payload, launched as a second stage from the booster, will have 340 tons of fuel remaining after reaching leo.
* a tanker with no payload, launched as a second stage from the booster, will have 710 tons of fuel remaining after reaching leo.
* a fully loaded ship - lets say 450 tons of cargo - with the help of a booster, reaches leo with 0.15 dv to spare (this is assuming the booster saves no fuel for reentry)
** from there, after full refueling, it can travel an additional 5.4 deltav
*** now from leo to mars landing without aerobraking or aerocapture is 10.2 deltav. So a fully loaded ship would have to do 10.2-5.4 = 4.8 dv worth of aerobraking/capture to land on mars at 0 m/s.

* the fuel capacity of the transport is 1950 tons, so that means it would take no more than 3 refuelings, if we assume no fuel is needed for reentry.

ltgbrown
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Re: SpaceX News

Postby ltgbrown » Sat Oct 01, 2016 9:09 pm

I wonder how big/how much a Polyell will be? Say, 100 MW.
Famous last words, "Hey, watch this!"

krenshala
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Re: SpaceX News

Postby krenshala » Sat Oct 01, 2016 11:29 pm

Mass is the big issue there, with size/volume only really being an issue while in atmosphere ... depending on configuration.

happyjack27
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Re: SpaceX News

Postby happyjack27 » Sun Oct 02, 2016 12:23 am

...updated my spreadsheet:

a "heavy" configuration (2 additional boosters) would weight about twice as much and deliver a little over twice the fuel in one launch.

(why not 3x? because you still only have 1 tanker)

so half as many launches, and half as many uses of the tanker (though 3/2 as many uses of the boosters)

the middle booster won't reach leo, so won't need to do a de-orbit burn. will be going a little over twice as fast than the side boosters were when it decouples.

presumably the middle booster engine configuration could be optimized (less thrust needed and spends more time in high altitude) to reduce mass and increase isp a little.


the tanker has a better full mass / empty mass ratio than the booster, AND has better isp. (the former presumably on the account of not needing so much thrust, and the latter on account of near vacuum.) consequently, by increasing the booster-to-tanker ratio, you're slightly increasing how much fuel you need to lift each ton of fuel. (from 12 tons per ton to 14 tons per ton)


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