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sweetplantveal t1_j7s2u0r wrote

The Raptor engines are unusual in that they can throttle down to 40% but as far as I know they still rely on turning some on and some off during different flight stages. If not takeoff and max q, for sure during landing. That coordination has to be super complex...

For context, the engine has been under development for a decade and testing for five years. It's a smaller engine than usual on heavy lift vehicles. It's height is 10 feet. The F1 engine from the Saturn V is almost twice as tall, could fit a Raptor sideways in its nozzle, and develops over 3x the thrust. But where the Saturn V has 5 F1s on the bottom, BFR has 33 Raptors. About twice the thrust in total.

This test is a big deal for Space X. A TON of their future plans hinge on the Raptor.

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upyoars OP t1_j7s62kc wrote

It’s also a full-flow staged combustion engine, the most complex but most efficient type of combustion engine possible. Meant for maximizing and optimizing efficiency to a ridiculous degree, squeezing every drop of juice possible. If it’s successful it would also be the first full flow stage combustion engine to ever be successfully operated and used in history.

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lapseofreason t1_j7trp7c wrote

Can you clarify what the efficiencies mean in practical terms ? Does it mean less fuel burn per unit thrust and less cost etc ? Why did they choose that technology ?

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CeeJayDK t1_j7tum7k wrote

See https://www.youtube.com/watch?v=LbH1ZDImaI8 or https://www.youtube.com/watch?v=Owji-ukVt9M

But if I understand it right, the temperatures when you drive a propellant turbine can get so hot they melt or otherwise break the turbine, so to get around this they normally burn the propellant in the preburner in a less optimal way with either too much oxygen or too much fuel.

The full flow engine however does both at the same time using two preburners and two turbines and the combined fuel and oxygen mix that reaches the main combustion chamber is optimal for the best combustion and it's super hot and in a gaseous form which helps it burn even more efficiently.

The downside is that it's probably twice the complexity and it's startup cycle is also very complex and must be managed precisely.

But it gets the most amount of thrust out of the available fuel of any current engine design today with the least amount of heat stress on the turbines - which you could use for added safety .. OR use to push the turbines even more to crazy pressures and more power. SpaceX does the latter.

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lapseofreason t1_j7u7una wrote

Thank you so much for taking the time to give such a good explanation.

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Bensemus t1_j7wdlho wrote

> If not takeoff and max q, for sure during landing.

They aren't turning any engines off during launch. Max Q doesn't' require a greater than 40% reduce in thrush.

Engines are turned off during separation. Then some are turned back on for the boost back burn and maybe a reentry burn. Then finally some are used for the landing burn.

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simplegrocery3 t1_j7sra1g wrote

I've misread it as firing all 33 Starship engineers at once

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PermaStoner t1_j7txrzu wrote

These Silicon Valley lay-offs are getting out of hand.

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MakingItElsewhere t1_j7st4ku wrote

For anyone as confused as I am: Yes, there are literally 33 engines at the bottom of that thing. And 6 more in the upper stage.

Here's an image which helped me: Naked Engines!

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drawkbox t1_j7u5ffp wrote

Got that Soviet N1 many engine vibe. Super complex and risky. So many more things that can go wrong with that many engines from production to runtime. The N1 never successfully launched.

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TheAssholeofThanos t1_j7u8oyk wrote

Alot of what made the N1 dangerous were things that SpaceX has been specifically trying to avoid. The N1s were never actually static fired before launch tests (individual components were tested separately, and it was assumed they would work in accordance). The Superheavy and Starship program has been slowly stepping up their series of static fires. This is also the 2020s, where we dont have to rely on technology like pyrotechnic valves (used because they were lighter) and have massive advances in guidance and metallurgy.

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drawkbox t1_j7uehzp wrote

Indeed there has been lots of progress since. It just seems needlessly complex, so many potential failures from all the valves/seals/connections/feeds/controllers/bonds etc. All the complexity of one engine, times thirty three.

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Bensemus t1_j7we29w wrote

They need multiple engines for landing. An empty Falcon 9 is already too light to hover or descend on a single Merlin engine at minimum throttle.

Both Starship and SuperHeavy can hover and descend with multiple Raptor engines firing. This gives them engine out capability while landing and a much safer landing profile. There's no need to perform a suicide burn where you only have a brief moment to get it right or you are crashing.

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MakingItElsewhere t1_j7u7drk wrote

I'd like to think advancements in technology are going to allow for faster response times in the event something doesn't do what it's supposed to do.

But I guess we'll all see how today's test goes, and what is learned from it.

Fingers crossed it goes well!

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[deleted] t1_j7rxy2e wrote

[deleted]

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bigbangbilly t1_j7slhm6 wrote

>Shotwell

If rockets are some sort of projectile then she definitely lives up to her name

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funkboxing t1_j7sm4h7 wrote

I am disappointed in myself for not coming up with a good moonshot-shotwell connection. Seems like an easy win but I just can't find it.

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kenrnfjj t1_j7sedrt wrote

Im confused what she does is she an engineer too or just sells the rockets. What does a COO do. And how different is it from ceo

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coldblade2000 t1_j7sw8ka wrote

> Gwynne Shotwell

From what I understand: As COO (Chief Operating Officer), she's basically in charge of running the company itself and making sure it's running at peak performance. Who to hire, tracking internal goals, evaluating the performance of middle management, etc. Whenever a company has plenty of people not doing anything, has big work bottlenecks, has useless managers, is ignoring laws & oversight, or is otherwise running in an inefficient manner, it is the COO's role to make sure those things get fixed. An engineer may or may not be good at that job. Management-oriented engineers, like industrial engineers, logistics or systems engineers would probably do well at a COO job, as long as they have plenty of managerial experience. A mechanical or electronic engineer that are top of their field but aren't necessarily managers would probably not be able to keep up in that role.

A CEO (Chief Executive Officer) is tasked with executive tasks, and is the primary ambassador for the company. By executive, I mean they are in charge of "making sure things are happening (being executed)". They ultimately decide and shape the directions the company will take in the medium and long term (acquisitions, looming market threats, new product lines, etc), and are also in charge of making sure stockholders and other stakeholders are kept happy. Often enough, they will be the ones who will ultimately face potential big investors, and represent their company in public (interviews and interrogations). CEOs are paid so disproportionately much not because their job is necessarily super hard (it depends, some are way more hands-on than others), but because their decisions carry the largest impact on the company's performance in the long run, so the pressure they are under is massive. A COO hiring a bad project lead, or a CTO (Chief Technology Officer) choosing a cloud service provider that was ultimately terrible, will not be as catastrophic to the company medium-term as a CEO deciding to branch out into a market the company is woefully unequipped to handle, or the CEO failing to secure crucial investments to finish a large project.

So Elon is CEO of SpaceX, Tesla and now Twitter, and he's famously a very involved CEO, at least in one of them at a time (he kind of neglects SpaceX and Tesla while he focuses on Twitter). Very likely, he made the final call on approving SpaceX's Starlink, which deviated from their core rocket-building business. He was also likely the one who ultimately decided Tesla should focus on expanding their production with Gigafactories, and launching Powerwall to branch into infrastructure projects. Not only that, but in these cases, he was certainly very involved in steering the course these projects would take, based upon the recommendations of his subordinates. You'll also recognize that it will be hard for you to name a single current Tesla, SpaceX or Twitter employee aside from him, and that is by design (especially since his companies have the habit of firing their PR teams). As CEO, he focuses all negative attention the company attracts on himself, and ideally liberates his team from that negative attention.

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funkboxing t1_j7sfap8 wrote

I'm not a c suite expert and not all c titles are equivalent between companies/industries, but as I understand it Shotwell is responsible for ensuring revenue, development, and production goals are on track. She hires and manages engineering project managers, and sets realistic expectations and sources for income to support those projects.

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bigbangbilly t1_j7sktcy wrote

Seems like those starship engines need to find new employment soon /s

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KedynTR t1_j7ubotj wrote

These tech layoffs are getting ridiculous, not even engines can keep a job.

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bomberstudios t1_j7ryo8x wrote

I read “firing all 33 Starship engineers” and thought that was very on brand for their CEO.

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ragnarmcryan t1_j7rvju3 wrote

I would like to congratulate us for our taxpayer dollars making this possible

Edit: snowflakes will downvote

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ThestralDragon t1_j7s5oc3 wrote

It wasn't a gift, you paid for services which were delivered

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funkboxing t1_j7sfx3d wrote

We paid to develop those services, but ownership of the results of all that development are privately held.

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coldblade2000 t1_j7sx63v wrote

If I have a construction company and am hired by the government to build them a warehouse, it doesn't mean the government then owns my fucking house

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funkboxing t1_j7w89bb wrote

A functional analogy would be if you accepted government funding to research and develop a new construction process that you'd then patent.

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coldblade2000 t1_j7w9l0y wrote

>you accepted government funding to research

It'd be nice if you actually pointed to this "research funding". I looked over and all the money SpaceX was given by NASA was "service contracts" which are fulfilled or being fulfilled, or the Commercial Crew Program. In this one, SpaceX didn't receive money in the first round. In the second, seed money was first given to a few companies like BlueOrigin, Boeing and SpaceX to develop technologies for crewed vehicles. In SpaceX's case, their proposal was making their ALREADY EXISTING Dragon capsule human-rated, and finishing its abort system. The Falcon 9 had already flown various resupply missions to the ISS by then. The rest of their funding was NASA paying SpaceX to render services, or specifically making changes to SpaceX's vehicles for NASA's purposes

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funkboxing t1_j7wclov wrote

I guess if you don't consider paying for services yet to be developed as funding research, then yeah- I suppose that didn't happen.

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Bensemus t1_j8flh1j wrote

It's not that simple. Blue Origin had issues in the HLS contract because they tried to avoid NASA's R&D sharing requirements. NASA allows some stuff to be reserved as trade secrets but not everything. Accepting NASA money means you need to share technology with NASA.

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hallowass t1_j7shwyu wrote

Same with the space shuttle, the cost to maintain the shuttle was nearly the same as just building a new one.

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funkboxing t1_j7siei7 wrote

The STS wasn't privately owned.

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Emble12 t1_j7u2mzo wrote

Why does it matter if it can get what NASA wants to space?

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funkboxing t1_j7uhz2m wrote

Why does it matter what subsidies we give the petroleum industry as long as they put gas in stations for us to buy?

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Emble12 t1_j7w62ju wrote

If they’re doing it cheaper and maintaining standard, sure

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funkboxing t1_j7w8f9x wrote

Then why do they need public funding?

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Emble12 t1_j7w9cxl wrote

NASA gets the public funding. They choose how to allocate it, such as contracts to launch companies.

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funkboxing t1_j7w9v7q wrote

NASA isn't privately owned.

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Emble12 t1_j7wa6hc wrote

Yes, it’s a government agency and allocated government funding. It’s then up to NASA to use that funding, such as investing in and buying contracts from private companies.

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funkboxing t1_j7wd0zm wrote

And if NASA contracts a company to develop a system you think the IP for that system should belong to the company?

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Emble12 t1_j7xvzgu wrote

Depends on the contract, for most old space contracts NASA takes operations and so should have more ownership, but for new space contracts the company takes most operations and so has a right to control their assets.

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quettil t1_j7v8a42 wrote

Yeah better to pay Boeing ten times as much for the same service.

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Bensemus t1_j7webin wrote

lol "same service". Boeing cant' even manage that. They are years behind delivering crews to the ISS despite getting more money initially and even managing to go back to NASA and get an extra billion.

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afterburners_engaged t1_j7s9e5d wrote

Did Spacex get any subsidies?

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coldblade2000 t1_j7sxt8l wrote

They got seed money from NASA, and plenty of contracts, but not much that could be considered a "subsidy". At worst, they may have gotten some fat contracts as an investment by NASA, who desperately needed private companies to fill the LEO hole, and quick.

https://en.wikipedia.org/wiki/History_of_SpaceX#Funding

Supposedly, by 2012, about half of their funding had been government contracts that provided down payments, while the rest were private investments. A year later, they would be undercutting the costs of the Ariane 5 and Proton-M

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AlexandersWonder t1_j7sdtyi wrote

NASA has contracts with them for their rockets. So in a way I guess some of our taxes might go to them. But not a lot, NASA has a pretty small budget compared with other government agencies

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afterburners_engaged t1_j7sk0oi wrote

But those are payment for services rendered or services that will be rendered right? A subsidies main purpose is to keep the cost of something low. Kind of like the $7500 income tax credit for electric cars

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AlexandersWonder t1_j7skurs wrote

it’s not a subsidy, I was just speculating as to why this first commenter brought up taxpayer dollars

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