SpaceX test flight of Starship SN-5 [video] • Hacker News Board

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

#331

Post by SEJeff » Thu, Aug 06, 2020, 3:50 AM UTC

HPsquared wrote: post #324

SEJeff wrote: post #304

Earlier quoted context omitted.

Why only turn it up to 11 when you can turn it up to 31? See the Starship dial goes all the way to 31.

Things have different scaling laws. Very large rocket engines might not be practical for a range of reasons: wall thickness required to contain the high pressures (this is probably a big one) combined with the temperatures, combustion instability, controllability, and general ability to manufacture. Why are elephants and ants differently shaped? Another example is piston engines: large ones generally have lots of (re…

I take it you've literally never seen this? https://www.youtube.com/watch?v=KOO5S4vxi0o

The joke went entirely over your head boss.

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

#332

Post by BenjiWiebe » Thu, Aug 06, 2020, 4:50 AM UTC

sandworm101 wrote: post #316

Robotbeat wrote: post #262

Earlier quoted context omitted.

It's not particularly hard. Just like with regular rocket upper stages that require multiple burns to complete the mission, you can use small ullage thrusters to settle the propellant and make sure liquid (instead of pressurant gas) is transferred from one tank to another. The physics is exactly the same as making sure the engine receives fuel. Just need the thrusters to be fired longer. SpaceX has done experiments w…

Yes but ullage thrusters would have to fire continuousky for the duration of the transfer. That is a significant burn time. If they are going to be draining the fuel using only the ullage thrust, it will take more than a slight nudge.

Wouldn't the thrust just be to settle the fuel so pumps could move it over?

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

#333

Post by Cogito » Thu, Aug 06, 2020, 5:11 AM UTC

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

I mean, feel free to be annoyed with the commentary, but there was no official live stream of the event.

There were 3-4 non-official live streams, I think all of them provided by people who have streamed every single one of these tests live.

Asking those people to not have a reaction when the thing actually flies is a little far-fetched, unreasonable, and contrary to what their audience wants and expects.

This isn't a reaction video with "some pre-packaged emotional reaction", it's sitting down to watch an historical event with friends - hardly a dumbing down of anything.

Even in the official streams of other events the hosts become emotional, and are often drowned out by the cheers of those around them. I really have no idea what it is you want or expect from these live streams.

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

#334

Post by cryptonector » Thu, Aug 06, 2020, 5:56 AM UTC

rbanffy wrote: post #82

ChuckMcM wrote: post #50

Always impressive to me. And I know that people will say "Yeah, basically the only thing 'new' here is the engine" but there are also a bunch of other things that struck me; It did the hop 'off balance' (the final version expects to have 3 raptor engines working together) so the engine out scenario for landing still seems pretty safe. There is something like four more advanced vehicles in the warehouse section at var…

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.

Single stage to orbit (from Earth) is not as efficient as two stages to orbit, and that's the reason it's not done. If SpaceX manages to deliver Starship and reuse it and its booster, that will be a huge improvement over any possible reusable SSTO. SSTO or otherwise, reentry and landing are difficult enough, but SSTO adds other difficult problems.

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

#335

Post by cryptonector » Thu, Aug 06, 2020, 5:59 AM UTC

mschuster91 wrote: post #209

ecpottinger wrote: post #99

Earlier quoted context omitted.

I think the Delta-X could have done the job, what went wrong was letting NASA taking control of it. Remember these are also the people who went with segmented solid fuel boosters, these were the people who thought the VentureStar with three new techs that all had to work at the same time but rejected the designs that did not need as much new tech, these are the people who let the SLS design go forward. The Delta-X wa…

The Wikipedia article on DC-X is interesting. > In a post-accident report, NASA's Brand Commission blamed the accident on a burnt-out field crew who had been operating under on-again/off-again funding and constant threats of outright cancellation. That is the reason why SpaceX is so much more efficient and revolutionary, compared to what Boeing/ULA on US side and EADS/Ariane on EU are doing - they are cutting politic…

Contractors like Boeing for SLS generally have sweetheart cost+ deals. They have zero incentives to cut costs -- nay, they have an incentive to increase costs because their profits are the "plus".

SpaceX isn't interested in a sweetheart subsidy deal. They are competing. That's why their contracts with NASA are fixed price: it gives SpaceX every incentive to keep costs down so as to maximize profit.

Surprise! SpaceX is doing better than the competition that gets sweetheart deals. It should really not be a surprise to anyone though, but it probably is to some.

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

#336

Post by garmaine » Thu, Aug 06, 2020, 6:25 AM UTC

jcun4128 wrote: post #329

HPsquared wrote: post #324

Earlier quoted context omitted.

Things have different scaling laws. Very large rocket engines might not be practical for a range of reasons: wall thickness required to contain the high pressures (this is probably a big one) combined with the temperatures, combustion instability, controllability, and general ability to manufacture. Why are elephants and ants differently shaped? Another example is piston engines: large ones generally have lots of (re…

I never quite got the Orion(nuclear?) engine design eg. is it literal "nuclear explosions" or just using nuclear as a heat source. I think they push fluid through the bells, maybe other materials(like ceramic) for the larger nozzles... can they use magnetic field to contain heat... probably not assumes it's ionized or something ha... heat still goes through magnetism. I got it, active heat destructive interface ha.

Literal nuclear explosions, Every few seconds, with a giant spring to even out the force.

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

#337

Post by hcknwscommenter » Thu, Aug 06, 2020, 6:51 AM UTC

BenjiWiebe wrote: post #332

sandworm101 wrote: post #316

Earlier quoted context omitted.

Yes but ullage thrusters would have to fire continuousky for the duration of the transfer. That is a significant burn time. If they are going to be draining the fuel using only the ullage thrust, it will take more than a slight nudge.

Wouldn't the thrust just be to settle the fuel so pumps could move it over?

You need acceleration to settle the fuel and to keep it there. Once the acceleration stops, the fuel begins to unsettle.

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

#338

Post by mschuster91 » Thu, Aug 06, 2020, 6:53 AM UTC

valuearb wrote: post #236

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!

This is a very key point. The Falcon 9 isn’t cheap because of reuse (yet). It’s cheap because of mass manufacturing. The Rs-25 engine costs over $100m each, Ariansoace Vulcains around $20M, typical large rocket engines over $10M. SoaceX Merlin costs about $200,000 each to make. The Raptor will be close to that. Thats why SpaceX can pursue the large number of redundant smaller engines design strategy so successfully.…

> Reuse has lowered Falcon 9 costs internally, and increased its private discounts, but not it’s public pricing

It's not just a discount - it is the reversed equivalent of banks charging interest for a loan due to failure risk. Private customers getting discounts accept the increased risk that some re-used part fails. Essentially SpaceX has managed to have their r&d subsidized by paying customers instead of having to borrow money, launch dummy payloads and pay the money back.

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

#339

Post by mschuster91 » Thu, Aug 06, 2020, 6:57 AM UTC

pfdietz wrote: post #288

throwaway0a5e wrote: post #224

Earlier quoted context omitted.

Africa was in Europe's back yard yet when they got the opportunity they colonized the Americas. Colonizing a formerly unexplored place where nobody has yet laid claim has a lot of appeal (and this time we (probably) don't have to kill/displace the natives to do it).

Europeans were kept out of Africa by disease.

I'd rather say the Europeans were kept out of Africa because of nowhere near European levels of valuable resources (think farmland, wood) other than slaves for centuries. Diamonds and uranium are a recent thing.

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

#340

Post by krisoft » Thu, Aug 06, 2020, 7:07 AM UTC

BenjiWiebe wrote: post #332

sandworm101 wrote: post #316

Earlier quoted context omitted.

Yes but ullage thrusters would have to fire continuousky for the duration of the transfer. That is a significant burn time. If they are going to be draining the fuel using only the ullage thrust, it will take more than a slight nudge.

Wouldn't the thrust just be to settle the fuel so pumps could move it over?

Usually when you ignite an engine on orbit a short kick of ullage trusters is enough. It is because once the fuel settled enough to start the engine the trust of the engine will keep the fuel settled. This is not true in the fuel transfer situation, there a single kick is not enough. If you are using ullage motors and not internal bladders, you have to keep producing the micro-trust for the whole transfer duration. Be mindfull that pumping a rocket-full of fuel won’t be an instantenous process.