SpaceX News

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

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kunkmiester
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Re: SpaceX News

Post by kunkmiester »

I wonder if they're gonna keep with the barge or try for more land landings to get stages to actually analyze. At this point I'd think they'd be able to get permission for more.
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ladajo
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Re: SpaceX News

Post by ladajo »

All indications are the next couple of flights are targeting barge landings.

I was poking around the NSF barge thread, and they have some good photos and video of ongoing barge repairs from the last lawn dart.
Not only did it perf the deck, but looks like it may have damaged the nearby outer bulkhead as well. The repairs have included a large section of stringers and under-deck support structure IVO the dart hole. I recommend running through the thread to the end.

SpaceX Barge Repairs
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

Giorgio
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Re: SpaceX News

Post by Giorgio »

Nice pics and also nice engineering drawings of the barge in the same thread.
Considering the way it is built I doubt we will ever see it gurgle even if the stage will pierce through it like a dart.
A society of dogmas is a dead society.

KitemanSA
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Re: SpaceX News

Post by KitemanSA »

D Tibbets wrote:I think I know what KitemanSA is getting at. If you can lift the full core to a higher altitude and give it some downrange speed, you have an advantage. This is like the air launched Pegasus or Virgin Galactic Space Ship 2 (or is it 3?). He is separating the effort to get to that point and ignoring associated costs.
Nope. I am comparing the cost of a throw away stage 1 to the cost of a reusable stage 1 with 2 or 4 reusable stage 0 (neutrally boosted fly back auxiliary tanks with crossfeed).

paperburn1
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Re: SpaceX News

Post by paperburn1 »

Goal one is to get as high as you can as fast as you can, Goal two is to get orbital speed for the height your planing to be at.
Neutrally boosted is something you just do not do. If it can push is should push as hard as it can as long as it can without breaking. The longer you stay in the boost zone the more fuel you will use to get to orbit. There is no cost advantage worth the effort.

The only reason they throttle back after launch is to keep in the design limit of the space craft until it passes the highest stress on the craft(MAX-Q).
After MAX-Q the stresses fall off fast and they throttle up to 100 percent as fast as the design limit allows. Astronaut comfort is secondary and if NASA though they could boost at ten G's and have usable workers then they would. But the limits are from as much as 20 g for less than 10 seconds, to 10 g for 1 minute, and 6 g for 10 minutes, and 4 g for 15 minutes for both eyeballs in and out.
This leaves the limit for functional astronauts after boost to be about 4 g so that now becomes your limit of how hard you can boost if you want anybody wake and functional when you get to orbit. The space shuttle rode at 3 to 3.5 g. but the shuttle was designed to carry (fragile) scientists rather than ex-military fighter jocks.
Mercury-Atlas missions were more dramatic; 1.35g off the pad, peaking around 7g just before the booster engines shut down and dropped away, climbing again to almost 8g before the sustainer ran out of fuel.
I am not a nuclear physicist, but play one on the internet.

DeltaV
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Re: SpaceX News

Post by DeltaV »

Atlas was originally an ICBM (based in Turkey during the 1962 Cuban Missile Crisis), adapted into a manned booster, hence the high g.

ladajo
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Re: SpaceX News

Post by ladajo »

Good point about the human aspect limits. These don't apply to unmanned though. Unmanned is about booster breakup, as you implied.
Now if you gave thise squishy science types a couple of years conditioning and some g-suits, now we'd be talkin'!
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

93143
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Re: SpaceX News

Post by 93143 »

It was Jupiter IRBMs in Turkey. Atlas, being an ICBM, could hit its targets from much further away.

There are old Atlas and Titan bases scattered all over the continental U.S.; I believe there was something of a fire sale on them a while back.

TDPerk
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Re: SpaceX News

Post by TDPerk »

"There is no cost advantage worth the effort."

That is true only for some definitions of "neutrally boosted" <-- still not clear everyone is on the same page on what that is, and I'm sure I'm not.

The boosters of such a stack as the Falcon Heavy are contributing as much of the lift-off thrust as the center stage, and they are supplying it's fuel until they have only the fuel remaining to permit them to be recovered (when the stack is used in a recoverable flight profile). This gets you around 12 minutes of burn out of a stage with what, nine minutes of tank? There is very little extra effort in designing and building the recoverable stage, and it is amortized over many flights.
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ladajo
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Re: SpaceX News

Post by ladajo »

I think we need to reconcile this with some numbers.
The two themes seem to be DeltaV matters or Isp matters.
It would appear that both should be considered, and also against the purpose of the mission.

If you are seeking to get more fuel to a given orbit, then it follows that you need more push to move more mass to sufficient speed. (More lifted mass goal)
If you are seeking to get to a higher speed to support a higher orbit or escape, then it follows you want to minimize mass and maximize boost (more speed goal).

What are we trying to do here?
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

TDPerk
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Re: SpaceX News

Post by TDPerk »

"What are we trying to do here?"

Lowest reliable $/lb to LEO.
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krenshala
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Re: SpaceX News

Post by krenshala »

ladajo wrote:I think we need to reconcile this with some numbers.
The two themes seem to be DeltaV matters or Isp matters.
It would appear that both should be considered, and also against the purpose of the mission.

If you are seeking to get more fuel to a given orbit, then it follows that you need more push to move more mass to sufficient speed. (More lifted mass goal)
If you are seeking to get to a higher speed to support a higher orbit or escape, then it follows you want to minimize mass and maximize boost (more speed goal).

What are we trying to do here?
Delta-v determines where you can go, while Isp determines how efficiently you can get there. The higher the Isp, the less fuel you need to use for the same applied impulse (thrust). But the delta-v required only changes if the start, destination or path between them changes. The Isp is part of the rocket equation to calculate the delta-v :

delta-v = (g_0 * I_sp) * ln(wetmass/drymass)

Where wetmass is the mass of the rocket including fuel, drymass is the mass of the rocket after the fuel has been consumed, g_0 is acceleration due to gravity (9.81 m/s2), and I_sp is specific impulse in seconds.

It takes approximately 9.5 to 10 km/s of delta-v to reach low earth orbit, regardless of the mass you are launching (as long as its an aerodynamic object flying a reasonably efficient ascent profile). If you change how the fuel mass is consumed, normally by changing the staging, you are directly affecting the delta-v calculations, and thus affecting how far/where the rocket can go.

If you guys are interested, I can throw together some screenshots showing how different staging of the same rocket can alter the delta-v it has available, and thus what it can do. I'm not a rocket scientist, but I've played about a thousand hours of Kerbal Space Program - while it is a somewhat simplified simulation (using 2-body, not n-body physics, for example), it does do the rocket equation stuff correctly, and can make for a simple way to demonstrate what kind of difference you will see between one-core, three-core-but-"neutrally boosted"-boosters, three-core, and three-core-with-fuel-cross-feed. (And yes, I freely admit its yet another excuse to fly rockets in KSP, that I was going to be doing tomorrow anyway. :D )

ladajo
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Re: SpaceX News

Post by ladajo »

Have at it.
My position mostly been based on the inverse relationship between dry mass and delta-v.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

krenshala
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Re: SpaceX News

Post by krenshala »

I'll whip up some comparisons tonight or tomorrow, then. I just need to wait for my 12h shift to end. At least its my friday ...

paperburn1
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Re: SpaceX News

Post by paperburn1 »

I think some hard point data of spacex ships would be great!
I am not a nuclear physicist, but play one on the internet.

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