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SpaceX test flight of Starship SN-5 [video]

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Re: SpaceX test flight of Starship SN-5 [video]

#161

Post by ben_w »

Someone wrote: post #155
pacificmint wrote: post #135

Earlier quoted context omitted.

> we are talking 19 launches per day […] isn't that completely impossible!?? The US uses over 20 million barrels of petroleum every single day. We have 44,000 airline flights every day. I think 19 starship flights won’t even move the needle.

https://en.wikipedia.org/wiki/SpaceX_Starship says a starship uses 3,400,000 kg (first stage) + 1,200,000 kg = 4,600,000 kg of propellant, both methane + liquid oxygen. Let’s guess making the fuel takes 5,000,000 kg of oil (corrections welcome. I guess that’s a reasonable estimate. Less than 100% of fuel is methane, but the specific energy of methane is about 20% higher than that of oil, and creating liquid oxygen ta…

Why count oil as the energy source for liquefying oxygen? Why not PV? Why not use natural gas instead of cracking oil?

Also, separate point: Starship return flight to Mars requires large-scale manufacture of methane from atmospheric CO2, using solar (or technically nuclear, but I don’t see that happening in this case).

It’s the only way of getting back — their tanks are empty when they finish landing on Mars — but it works fine here too.

Re: SpaceX test flight of Starship SN-5 [video]

#162

Post by wcoenen »

themgt wrote: post #52
llboston wrote: post #43

Earlier quoted context omitted.

Another significant thing is that Starship is designed to be mass manufactured at a relatively low cost. SpaceX can crank out thousands of Starships, fly them to Mars and build a million people colony. Starship is truly a game changer!

Yep, and in addition to both of these, Starship is also designed: * to be fueled / ignited such that it can be refueled in-situ on Mars & then launched back to Earth, without advanced rocket fuels or the TEA-TEB chemical igniter. * to be able to refuel from another Starship in-orbit The combination of all of this, if they pull it off, will be the ability to send truly massive payloads to Mars, faster and cheaper than…

> * (or "we can put a couple humans on Mars for 3 days for $100 billion")*

Is there actually a NASA proposal like that? As far as I know, orbital dynamics don't allow for this. One has to wait for a Hohmann transfer orbit window to return home.

Re: SpaceX test flight of Starship SN-5 [video]

#163

Post by garmaine »

wcoenen wrote: post #162
themgt wrote: post #52

Earlier quoted context omitted.

Yep, and in addition to both of these, Starship is also designed: * to be fueled / ignited such that it can be refueled in-situ on Mars & then launched back to Earth, without advanced rocket fuels or the TEA-TEB chemical igniter. * to be able to refuel from another Starship in-orbit The combination of all of this, if they pull it off, will be the ability to send truly massive payloads to Mars, faster and cheaper than…

> * (or "we can put a couple humans on Mars for 3 days for $100 billion")* Is there actually a NASA proposal like that? As far as I know, orbital dynamics don't allow for this. One has to wait for a Hohmann transfer orbit window to return home.

There are faster transfer opportunities, but not 3 days. But I think he way saying 3 days of surface ops. Which is still an exaggeration. I think the NASA reference mission is 30 days?

Re: SpaceX test flight of Starship SN-5 [video]

#164

Post by Tuna-Fish »

Someone wrote: post #155
pacificmint wrote: post #135

Earlier quoted context omitted.

> we are talking 19 launches per day […] isn't that completely impossible!?? The US uses over 20 million barrels of petroleum every single day. We have 44,000 airline flights every day. I think 19 starship flights won’t even move the needle.

https://en.wikipedia.org/wiki/SpaceX_Starship says a starship uses 3,400,000 kg (first stage) + 1,200,000 kg = 4,600,000 kg of propellant, both methane + liquid oxygen. Let’s guess making the fuel takes 5,000,000 kg of oil (corrections welcome. I guess that’s a reasonable estimate. Less than 100% of fuel is methane, but the specific energy of methane is about 20% higher than that of oil, and creating liquid oxygen ta…

> corrections welcome.

Methane is not made from oil. It's either directly pumped out of the ground as natural gas, or collected from organic decay processes. Methane is more carbon-efficient, as it has almost 2x more hydrogen per carbon compared to longer hydrocarbon fuels, and most of the energy in the molecule is in the hydrogen, to the tune of 40% more energy per ton of CO2. One ton of methane burnt produces ~2.7 tons of CO2 (and 2.2 tons of water), compared to one ton of octane producing 3.1 tons of CO2 (and 1.4 tons of water).

Of the propellant in the rocket, less than a quarter is methane, and more than 3/4ths are LOX. The stoichiometric ratio would be ~1:4 (by mass), but for various reasons most rocket engines are more fuel-efficient when burning fuel-rich, so the real ratio is probably somewhere between 1:3.6 to 1:3.8. The energy cost of producing LOX is really, really low, less than 1% of the energy content of similar mass of methane. Also, this process is done with electricity, and is very amenable to intermittent production. (So the CO2 impact is effectively zero).

Coming from the other direction, according to the department of energy, the US yearly CO2 emissions from all anthropogenic sources are ~6.7B tons of CO2 equivalents, while the launch of a single SS/SH produces about 2700 tons. If you were launching a thousand of them every year, they would account for 0.04% of emissions.

Re: SpaceX test flight of Starship SN-5 [video]

#165

Post by garmaine »

skissane wrote: post #104
rbanffy wrote: post #97

Earlier quoted context omitted.

A country is friendly until it isn't. I understand it's not a requirement imposed by SpaceX, but it also prevents them from getting a lot of applications they wouldn't be able to turn into hires.

> A country is friendly until it isn’t If the US can trust the UK with information on nuclear weapon designs and delivery systems, surely it can handle a few UK citizens working for SpaceX? In the unlikely event that the UK and US had some falling out, the US government could always order SpaceX to lay off UK citizen employees.

> If the US can trust the UK with information on nuclear weapon designs and delivery systems.

Bad example. The soviets got the bomb because of British spies in the Manhattan project. After that, there was very little collaboration to this day.

Re: SpaceX test flight of Starship SN-5 [video]

#166

Post by garmaine »

iso947 wrote: post #118
rbanffy wrote: post #82

Earlier quoted context omitted.

The DC-X still manages to look modern next to it. Had it succeeded, it'd have done something not even SpaceX is doing, which is a fully reusable single-stage-to-orbit craft. I don't think we have the advanced materials for that.

In theory starship will have the delta v to get to LEO and back in a single stage, but the payload would be so small it wouldn’t be worthwhile.

Incorrect, it couldn’t get back. The landing fuel and reentry structures would make it weigh too much. But as a demo they have considered a one-way orbital SSTO trip that’ll burn up on reentry.

Re: SpaceX test flight of Starship SN-5 [video]

#167

Post by skissane »

garmaine wrote: post #165
skissane wrote: post #104

Earlier quoted context omitted.

> A country is friendly until it isn’t If the US can trust the UK with information on nuclear weapon designs and delivery systems, surely it can handle a few UK citizens working for SpaceX? In the unlikely event that the UK and US had some falling out, the US government could always order SpaceX to lay off UK citizen employees.

> If the US can trust the UK with information on nuclear weapon designs and delivery systems. Bad example. The soviets got the bomb because of British spies in the Manhattan project. After that, there was very little collaboration to this day.

What about the 1958 Mutual Defence Agreement? That led to sharing of nuclear weapons design information, over a decade after the Manhattan project.

https://en.m.wikipedia.org/wiki/1958_US–UK_Mutual_Defence_Ag...

Re: SpaceX test flight of Starship SN-5 [video]

#168

Post by StevenWaterman »

sfjailbird wrote: post #130

Thank God for that guy in the corner helping me to know how to feel. Seriously though, this has been an incredibly annoying trend for a few years, everything has to be tagged with some pre-packaged emotional reaction. Such a dumbing down of public discourse. Someone linked the official video and it's amazing: https://youtu.be/s1HA9LlFNM0

The people watching that livestream are there specifically for him, he's a well-known personality in that community.

If you don't want that, there's other streams without presenters, or with less obnoxious presenters.

Re: SpaceX test flight of Starship SN-5 [video]

#169

Post by garmaine »

m4rtink wrote: post #54
app4soft wrote: post #23

Earlier quoted context omitted.

This is a prototype of the bottom part for the upper (second) stage of SpaceX 's next-gen rocket — Starship .

While it does not look that way without the pointy nose cone, this is the prototype of the second stage. The first stage will be a bit longer than this & its build enclosure is already being uilt.

That’s what he said.

Re: SpaceX test flight of Starship SN-5 [video]

#170

Post by garmaine »

skissane wrote: post #167
garmaine wrote: post #165

Earlier quoted context omitted.

> If the US can trust the UK with information on nuclear weapon designs and delivery systems. Bad example. The soviets got the bomb because of British spies in the Manhattan project. After that, there was very little collaboration to this day.

What about the 1958 Mutual Defence Agreement? That led to sharing of nuclear weapons design information, over a decade after the Manhattan project. https://en.m.wikipedia.org/wiki/1958_US–UK_Mutual_Defence_Ag...

Read the details; it wasn’t free exchange of information. It was basically a way for the US to allow sales of some nuclear plants and material, and sharing of design work only when it overlapped significantly with what the UK already did.
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