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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]

#241

Post by baq »

chrisjc wrote: post #233
mpweiher wrote: post #128

Earlier quoted context omitted.

> game changer Absolutely, and the quantitative analysis is just stunning. In 2018 all of humanity launched a total of 111 payloads into space (out of 114 attempts). At around 5t per launch, that would be 555 tons. Starship is supposed to have a payload to LEO of > 100 tons. So 5-6 launches would handle all of that, by weight. But SpaceX says their goal is to fly these up to 3 times a day. So let's assume they can do…

Perhaps a stupid and naive question, but is there even the demand to lift that much mass into orbit? I may just be lacking in imagination. Obviously most of that mass would have to leave orbit in order for it not to end up looking like an LA freeway in rush hour. edit: i guess propellant/fuel would be one of the heaviest and important payloads we would need to get up there.

starlink/oneweb/similar constellations, assuming US folks really hate comcast as much as they say on the intertubes. these are up to 12k sats with very short (couple years?) life time, so regular flights will be necessary to keep the fleet at desired capacity. this beast can lift i-don't-even-know-how-many hundreds of birds in one go.

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

#242

Post by xcskier56 »

njarboe wrote: post #218
dgritsko wrote: post #208

Earlier quoted context omitted.

> the most advanced rocket engine ever made Would love to learn more about this, can you expand? What makes Raptor so unique?

I am not a rocket scientist, but one of the main reasons it is so unique is that it will be the first full-flow staged combustion rocket engines to successfully be used on rockets. Rocket engines have powerful turbo pumps to move large amounts of fuel quickly to the combustion chamber to create thrust. Usually these pumps are powered by burning some of the propellant in a turbine and exhausting the resulting gas on t…

To add on, one of the biggest challenges with a full flow staged combustion engine is that the exhaust gas from the oxidizer rich turbopump is almost pure gaseous oxygen at very very high temperature. This combination likes to corrode and eat away any thing, metal included.

To solve this, SpaceX had to develop special metal alloys that could withstand this incredibly corrosive environment for long durations.

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

#243

Post by Allower »

tjtrapp wrote: post #63
bfieidhbrjr wrote: post #55

Does anyone else get super depressed by this? I did some great work today. I coded something pretty cool and useful. I built a little deck to explain it. My coworkers loved it. My job security went up. I enjoyed it. The journey is the reward. But these guys are making rockets in tents. Should I be rethinking life? Because that's how it feels. I love it. I admire them. But it feels unobtainable. I want to make that ki…

We're hiring for Starship and Starlink software teams: https://grnh.se/080f65d02us It sounds like you're passionate about your work and that's an important quality. As gorgoiler points out, "Making a difference in the world is what counts." If you'd like to help, consider applying! :)

Sounds cool, but I value my sleep ;-)

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

#245

Post by sandworm101 »

martythemaniak wrote: post #205

I really love the out-in-the-open development process. It doesn't cost SpaceX anything, yet they attract lots of internet media where people set up streams, discuss progress etc. The next year should be pretty exciting as they develop things further. Starship has a number of big innovations, which are: - the raptor engine. This was developed behind closed doors and is sort of finished. We won't see much of it, but it…

>> - in-orbit refueling. Starship is big and heavy and basically can't get anywhere unless it's re-fueled in orbit.

This is one of those "let's see" things that SpaceX has talked about but never actually explained. Their current rocket tech offers no hint as to how this is might happen. They aren't running internal bladders in their tanks. So the physical act of moving fuel from one tank to another is an open question.

The options are really limited. Either you use an internal bladder, something never done with cryogenic fuels, or some sort of maneuver to shift all the fuel over towards the pump. Maybe they plan on docking the two ships and then spinning the entire rig to create sufficient G to stabilize the fuel on one side of the tank? The entire operation seems more kerbal than reality atm.

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

#246

Post by bryanlarsen »

dgritsko wrote: post #208
martythemaniak wrote: post #205

I really love the out-in-the-open development process. It doesn't cost SpaceX anything, yet they attract lots of internet media where people set up streams, discuss progress etc. The next year should be pretty exciting as they develop things further. Starship has a number of big innovations, which are: - the raptor engine. This was developed behind closed doors and is sort of finished. We won't see much of it, but it…

> the most advanced rocket engine ever made Would love to learn more about this, can you expand? What makes Raptor so unique?

There are two main metrics of rockets and rocket engines. Specific Impulse (ISP), and the Thrust to Weight Ratio (TWR).

ISP is essentially a measure of the fuel efficiency. And since there are no gas stations in space, the further you can go per kg of fuel, the further you can go, period.[1]

TWR is the measure of useful power.

TWR is the key measure for the first stage because a ton of power is required to escape Earth's gravity and atmosphere. For subsequent stages ISP is the main metric.

The Space Shuttle Main engines have an excellent ISP but because hydrogen needs massive tanks, it has a crappy TWR. Which is why the shuttle had a couple of strap on solids with a high TWR.

But instead of specialized engines, SpaceX designs engines that are good at everything. The ISP isn't as high as an advanced hydrogen engine and the TWR isn't as good as a solid, but both numbers are quite respectable and they bring other advantages such as the ability to relight and to be reused without refurbishment, they don't need use ablative cooling.

1: Although SpaceX is relying on in flight refueling for it's Moon and Mars plans. Nobody's done it before, but that doesn't stop SpaceX.

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

#247

Post by napier »

martythemaniak wrote: post #205

I really love the out-in-the-open development process. It doesn't cost SpaceX anything, yet they attract lots of internet media where people set up streams, discuss progress etc. The next year should be pretty exciting as they develop things further. Starship has a number of big innovations, which are: - the raptor engine. This was developed behind closed doors and is sort of finished. We won't see much of it, but it…

> any upcoming engine that can compete with it.

There's the criminally underfunded SABRE engine, an a air-hydrogen mix breathing-rocket hybrid design from Reaction Engines that rated to reach speeds of Mach 25 (roughly 35,000 miles per hour).

As modelled, it's more efficient than any other current or proposed chemical propulsion technology, and the proposed single-stage runway launchable system would be capable of delivering around 11 tons of cargo to the ISS. The costs to go to orbit and beyond using this engine could be less than half that of current best in class technology; even less after development cost amortization. Not sure why SpaceX haven't invested in it yet. Perhaps it doesn't fit in with their current vertical integration philosophy, but it seems like a game changing technology.

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

#249

Post by mabbo »

napier wrote: post #247
martythemaniak wrote: post #205

I really love the out-in-the-open development process. It doesn't cost SpaceX anything, yet they attract lots of internet media where people set up streams, discuss progress etc. The next year should be pretty exciting as they develop things further. Starship has a number of big innovations, which are: - the raptor engine. This was developed behind closed doors and is sort of finished. We won't see much of it, but it…

> any upcoming engine that can compete with it. There's the criminally underfunded SABRE engine, an a air-hydrogen mix breathing-rocket hybrid design from Reaction Engines that rated to reach speeds of Mach 25 (roughly 35,000 miles per hour). As modelled, it's more efficient than any other current or proposed chemical propulsion technology, and the proposed single-stage runway launchable system would be capable of de…

> Not sure why SpaceX haven't invested in it yet

> an a air-hydrogen mix breathing-rocket hybrid design

Tough to use a breathing rocket anywhere but Earth. And SpaceX's goal is to use this to land on the Moon, Mars, everywhere.

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

#250

Post by credit_guy »

joakleaf wrote: post #132
mpweiher wrote: post #128

Earlier quoted context omitted.

> game changer Absolutely, and the quantitative analysis is just stunning. In 2018 all of humanity launched a total of 111 payloads into space (out of 114 attempts). At around 5t per launch, that would be 555 tons. Starship is supposed to have a payload to LEO of > 100 tons. So 5-6 launches would handle all of that, by weight. But SpaceX says their goal is to fly these up to 3 times a day. So let's assume they can do…

Indeed these numbers are impressive, but can it even be done? Is it even possible both in terms of climate change/overall environmental impact, and in terms of how much methane (fuel) we actually have. Elon Musk's vision is getting 1 million people to Mars (if I remember correctly) within this century. 100 per starship will require 10000 launches. Distributed over 70 years, that's about 1300 Martian voyages per year.…

Emissions calculation for Starship:

- each starship burns 4600 tons of methalox fuel

- the mixture ratio of the propellent is 78% O2 and 22% CH4 [1]

- that means that each 100 tons of methalox results in 53.6 tons of CO2 and 2.5 tons of CH4

- generally in the climate science it is accepted that one ton of CH4 is equivalent to 25 tons of CO2

- overall, each 100 tons of propellent will produce 116 tons of CO2-equivalent emissions

- a single launch of 4600 tons propellent will result in 5.34 kT CO2 emissions

- if we get to 5000 launches per year we end up with about 25 MT of CO2-equivalent emissions

- the current worldwide level of emissions is 45 GT CO2-equivalent as of 2017 [2]

- that means 5000 launches will increase our global emissions by 0.06%

[1] https://twitter.com/elonmusk/status/1258580078218412033

[2] https://en.wikipedia.org/wiki/List_of_countries_by_greenhous...

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