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

Postby kunkmiester » Fri Jan 04, 2019 7:13 pm

So how does the need to spend weight on more shielding affect the weight savings?
Evil is evil, no matter how small

paperburn1
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Re: SpaceX News

Postby paperburn1 » Sat Jan 05, 2019 12:41 am

I thing all things considered the weight penalty is small.
I am under the opinion that this is Nasa driven. I can see the fossils at nasa being afraid of composites because lack of testing and proof, but the 300 series steel is flight proven and used on a lot of vehicles. It does have a well document high temperature profile that is understood. Carbon fiber is not as well understood nor is the shielding requirements. To get that flight approved crew rating I believe they made a compromises to keep Nasa happy. Nasa is known for an arbitrary high number of test flights/ testing on new products before being accepted for crew rated. I am willing to bet the steel configuration has less flights and allows then to get more business. IMHO
I am not a nuclear physicist, but play one on the internet.

Maui
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Re: SpaceX News

Postby Maui » Sat Jan 05, 2019 3:45 am

I dunno— Musk seemed pretty excited about this when he first tweeted about the “delightfully counterintuitive” design change they had in store. Musk seems pretty transparent in expressing his feelings; I’m betting this came from SpaceX, not a NASA compromise.

paperburn1
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Re: SpaceX News

Postby paperburn1 » Sat Jan 05, 2019 10:42 pm

Or maybe a totally different problem is being fixed by the SS
https://www.wired.com/story/a-spacex-de ... g-the-iss/
I am not a nuclear physicist, but play one on the internet.

paperburn1
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Re: SpaceX News

Postby paperburn1 » Sun Jan 06, 2019 2:57 pm

paperburn1 wrote:Or maybe a totally different problem is being fixed by the SS
https://www.wired.com/story/a-spacex-de ... g-the-iss/

Edit
but the more I read and think about it Nasa might be clipping wings on this new bird. I just read the bracket report and I thing they are so resistant to risk they will not support carbon fiber until a large amount of testing is done. Spacex spent a huge amount on tooling to suddenly change directions so quickly. Just a point to ponder. any other thought out there?
I am not a nuclear physicist, but play one on the internet.

Skipjack
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Re: SpaceX News

Postby Skipjack » Mon Jan 07, 2019 6:47 am

paperburn1 wrote:
paperburn1 wrote:Or maybe a totally different problem is being fixed by the SS
https://www.wired.com/story/a-spacex-de ... g-the-iss/

Edit
but the more I read and think about it Nasa might be clipping wings on this new bird. I just read the bracket report and I thing they are so resistant to risk they will not support carbon fiber until a large amount of testing is done. Spacex spent a huge amount on tooling to suddenly change directions so quickly. Just a point to ponder. any other thought out there?

I don't think that NASA has anything to do with it. Elon Musk himself said that it was because it was the better solution. My guess is that SpaceX has developed a new stainless steel alloy that is maintaining enough strength at high temperatures that it can be used without any TPS. Without a TPS, a stainless steel version might actually end up being lighter than the carbon composite version. Even if were to be slightly heavier, it would still have the operational benefit of not needing a TPS that potentially needs a lot of service between flights. Given the proposed uses for the Starship (including going to the Moon and Mars and regular intercontinental passenger flights), this by itself is very important.

Dragon is not made from CC. It is made from AlLi. The out gassing really is a non problem that has been blown out of proportion. So this has nothing to do with it.
Also Starship is not a NASA project. So NASA has no say in it. Besides congress wants NASA to keep using SLS and Orion, so that NASA funds can go to certain large defense contractors in the districts of certain senators and congress men.

Maui
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Re: SpaceX News

Postby Maui » Wed Jan 09, 2019 12:08 am

A new Ars Technica article backs the idea that Musk is excited about the Starship design changes:
But above all these things, Musk is a geek at heart, in the sense that geek means a "knowledgeable and obsessive enthusiast."

He is knowledgeable about rockets and obsessed with their details. In sharing all of these tidbits about Starship, Musk is telling the world that he is really (really) freaking excited about Starship.


It goes on to provide a good summary of what we've learned from his recent tweets:
* The vehicle's exterior will be made from a stainless-steel alloy that will not buckle and will remain stable on the launchpad even when unpressurized. The strength and weight of "full hard stainless" at cold temperatures is slightly better than carbon fiber, at room temperature it is worse, and at high temperature it is vastly better.

* The metallic skin of Starship will get too hot for paint, so it will have a stainless mirror finish. It will need much less shielding as a result, and areas that take the brunt of atmospheric entry heating will be activity cooled with residual liquid methane. As a result, "Starship will look like liquid silver."

* A "radically redesigned" Raptor engine will be ready for test firing early this year. This is the engine that will power both the first stage "Super Heavy" as well as the Starship. For the test hopper, there will be three Raptor engines (there will be seven on the full Starship). Engines currently on the vehicle are essentially mock-ups. The first engine for hopper test flights "is almost finished assembly in California."

* SpaceX developed a "superalloy" to withstand the incredible pressures inside the Raptor engine and its hot, oxygen-rich gas. "Our superalloy foundry is now almost fully operational. This allows rapid iteration on Raptor."

* Musk expects the first hopper tests to occur in March or April of this year, sooner than expected. "I will do a full technical presentation of Starship after the test vehicle we're building in Texas flies."

* Musk believes a single-stage-to-orbit launch from Earth is "pointless." A large booster is needed to escape Earth's gravity well if one wants a decent-sized payload. But the single-stage Starship alone is great for launching from Mars and the moons of the Solar System.

Skipjack
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Re: SpaceX News

Postby Skipjack » Sat Jan 12, 2019 3:13 am

I still wished that they had looked into making the Starship and SSTO for launching Starlink satellites. Yes, payload would be small, but enough for Starlink. Starlink will need hundreds of launches. That would be a great way to get operational experience quickly and SSTOs have a (small) operational advantage over TSTOs.

Giorgio
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Re: SpaceX News

Postby Giorgio » Sun Jan 13, 2019 9:41 am

As you said payload would be smaller.

If I remember correctly the total mass ratio difference for a DV=7.5km/sec with a 300 ISP fuel for a SSTO to a TSTO would be roughly 20 (SSTO) to 5 (TSTO). That means you loose 4 times the amount of mass you can bring to a DV=7.5Km/sec. And because the "mass" is the weight of the payload+rocket structure, it means that your payload mass can easily drop to 1/10th when you choose a SSTO system instead of a TSTO system.

Considering that they have a limited time frame to place in orbit the system, increasing the number of satellite they put in orbit in a single launch is the safest route (as well as the most economical one).
Look, stars!

choff
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Re: SpaceX News

Postby choff » Mon Jan 14, 2019 8:10 am

Saw a report SpaceX is laying off 10% of the workforce.
CHoff

Giorgio
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Re: SpaceX News

Postby Giorgio » Wed Jan 16, 2019 7:41 pm

choff wrote:Saw a report SpaceX is laying off 10% of the workforce.

As any seasoned farmer can confirm, regularly pruning a tree keeps it healthy and spurs fresh growth in the remaining branches.
Look, stars!

Maui
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Re: SpaceX News

Postby Maui » Wed Jan 23, 2019 12:46 am

Elon Musk: Why I'm Building the Starship out of Stainless Steel
I was contemplating this for a while. And this is somewhat counterintuitive. It took me quite a bit of effort to convince the team to go in this direction. But now I believe they are convinced—well, they are convinced.

So that certainly clarifies that NASA wasn't the reason behind this decision. But while it's hard to knock his track record, this kind of statement makes me worried that he knows just enough to be dangerous. I think I would have felt better if this is something that had bubbled up from ongoing design work at a lower level.

The thing that’s counterintuitive about the stainless steel is, it’s obviously cheap, it’s obviously fast—but it’s not obviously the lightest. But it is actually the lightest.

But Musk also at one point claimed that installing a solar roof would cost less than putting on a standard roof. Anxious to see numbers that support this.

paperburn1
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Re: SpaceX News

Postby paperburn1 » Wed Jan 23, 2019 4:18 am

Sooooo Elon said "Regenerative heat shield. A double-walled stainless shell—like a stainless-steel sandwich, essentially, with two layers. You just need, essentially, two layers that are joined with stringers. You flow either fuel or water in between the sandwich layer, and then you have micro-perforations on the outside—very tiny perforations—and you essentially bleed water, or you could bleed fuel, through the micro-perforations on the outside."

Or to put it another way "My shiny spaceship will fart it's way down to a landing"
¯\_(ツ)_/¯

Seriously this idea has been used in commercial aviation before in hot section blades, it also has been used in the ru68 rocket engine and others.
We have a madman with a spaceship here folks, nothing to see just move along.
Next thing he is going to tell us is that it is bigger on the inside.
I am not a nuclear physicist, but play one on the internet.

Maui
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Re: SpaceX News

Postby Maui » Wed Jan 23, 2019 6:22 pm

The Starship hopper was destroyed last night by a storm :(
https://forum.nasaspaceflight.com/index ... msg1904371

Skipjack
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Re: SpaceX News

Postby Skipjack » Wed Jan 23, 2019 10:33 pm

Maui wrote:The Starship hopper was destroyed last night by a storm :(
https://forum.nasaspaceflight.com/index ... msg1904371

Only the "fairing" part of it. The part with the tanks and "legerons" is fine. The rest was built in a few days. So it should be an easy repair.


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