Arenenud riikide kosmosetehnika

[klaasmees]

Ehk võiks jääda ikka faktide juurde. Saan aru et isik ei meeldi aga enda oletused või arusaamad võiks ikka eraldi välja tuua. Meil siin käivad ajakirjanikud isegi lugusi otsimas siis pärast loeme ajalehest et " yes sir " oli sees ja Musk viskas kätt ka.

Kui mõni ajakirjanik ei hammusta irooniat läbi ja ei vaevu foorumi postitust teisest allikast üle kontrollima, oleks tal nagunii aeg ametit vahetada. Et ma ei muretseks. Saakski teada, kes ajakirjanikest tegelikult oma ametit ei vääri.

[Kriku]

2% tõenäosust, et YR4 tabab 2032. aastal punast ala:

[onu juulius]

Lisaks ka väike ex-twitteri animatsioon, mis näitab, kuidas see punane ala on saadud:
https://x.com/tony873004/status/1889025529388707970
Praegu pole võimalik täpsemalt määrata, millises antud joone punktis see asteroid tollel ajahetkel asub. Järgmisel lähenemisel 2028 (mis on ohutu) tehakse ilmselt täpsemad mõõtmised, kosmoseteleskoobi abil võibolla ka varem.

Täiendus: viimaste päevade vaatluste põhjal on kokkupõrke tõenäosus kasvanud 3,1%-ni. Asteroidi läbimõõt ~55m, kiirus 17,3 km/s, kokkupõrke energia ~7,8 Mt.

[NAFO ep]

Elon Muscovich Muski Starshipi uue prototüübi katsetus ebaõnnestus, rakett plahvatas mõningad minutid peale starti:

https://bsky.app/profile/peterbakernyt. ... qusfehfs2m

https://x.com/nexta_tv/status/1897904813930602710?s=46

[tsivi_list]

Elon Muscovich Muski Starshipi uue prototüübi katsetus ebaõnnestus, rakett plahvatas mõningad minutid peale starti:

Starshipi kuuest mootorist lülitus välja neli. See põhjustas juhitavuse kaotuse ja side katkemise sõidukiga. Rakendus kõigisse kosmosesõidukitesse sisse ehitatud enesehävitussüsteem.

Rohkem infot kaheksanda lennu kohta https://en.wikipedia.org/wiki/Starship_flight_test_8

[nukkel]

Homme SpaceX saadab oma raketi üles et need 2 tagasi tuua.https://abcnews.go.com/US/spacex-missio ... =119628164

[nukkel]

Need 2 tagasi maa peal.https://www.yahoo.com/news/nasa-astrona ... gTe-aGI2_e

[onu juulius]

"Need kaks" ei ole ju veel tagasi maa peal. Vahetusmeeskond läks alles orbiidile ja pole veel isegi kosmosejaama jõudnud. Siis läheb veel mitu päeva sisseelamiseks ja tööde üleandmiseks. Eelmine meeskond koos "nende kahega" peaks alla tulema 21. märtsi paiku.

[Porutšik]

Video Crew Dragon kosmoselaeva põkkumisest Rahvusvahelise kosmosejaamaga.

https://www.youtube.com/watch?v=QTFbMxS ... el=SciNews

ja ka ERRi uudis sel teemal.

https://www.err.ee/1609634732/nadala-as ... ale-naasma

[Gideonic]

Veidi materdavat infot Starshipi kohta. Eks teadjamad oskavad kommenteerida kas päris jama või mitte. Autor igatahes on ise kiirpaatide insener nii et mingi knowhow on. Mulle tundus et kui hüperboolne avaparagrahv kõrvale jätta on veidi infot küll. Seda kindlasti ei tohi puhta tõepähe võtta, aga tasuks kontrollida uusi starte jälgides:

https://www.planetearthandbeyond.co/p/s ... -beginning

Arvestades Muski viimaste aastate käitumist, Cybertruck'i projekti seiku, siis isegi kipun uskuma seda viimast tsitaati.

SpaceX constructs Starships well ahead of time, as they take months to build. This means that the most recent launch couldn’t have had its design optimised to resolve the issues shown in January’s failure. And their payload shows this. The January test had a dummy cargo equivalent to 10 Starlink V2 satellites, weighing only eight tonnes or 8% of its designed payload. Meanwhile, the most recent test had just half of this in a transparent attempt to reduce vibration by reducing the load to spare the obviously flawed fuel system, which obviously didn’t work.

However, this is only true in the short term. The Starships SpaceX will build from here on will have this issue fixed. Right?

Well, no.

These tests were the first launches of Starship Version 2 (Block 2). This iteration is longer to accommodate more propellant, has smaller forward flaps to ensure they don’t fail during landing, and has a redesigned fuel line system.

The previous version of Starship had major fuel delivery issues, causing engines to fail repeatedly, and SpaceX has made the situation worse by trying to solve this problem in the long term! This is the complete opposite of iterative design, and despite what Musk says, it’s a gargantuan setback (read more here).

But why has SpaceX failed to solve this problem? Well, it’s because of the bane of any rocket scientist: physics.

Landing the Super Heavy Booster is a far, far easier task than landing the Starship from orbit.

The Super Heavy Booster weighs 160 tonnes dry, doesn’t make it to space, and its peak speed is only roughly 4,600 mph. Meanwhile, Starship has a dry mass of around 150 tonnes, makes it to space, and reaches an orbital speed of at least 17,500 mph. This means that during landing, Starship has over 13.57 times the kinetic energy of the Booster! And that doesn’t account for the fact that Starship carries significantly more propellant during landing than the Booster.

All that energy has to go somewhere, and managing that is one hell of an engineering challenge. On top of that, Starship’s landing is also far more complex, as it has to reenter the atmosphere at those speeds. Not only does this process present significant aerodynamic challenges, but it also exposes Starship to enough heat energy to literally melt every gram of steel it is made from.

Okay, so what does that have to do with Starship’s repeated failures?

One word: weight.

The Block 1 tests of Starship showed that Musk’s plans to rely heavily on a bellyflop manoeuvre during reentry to slow down Starship and scrub off that kinetic energy using atmospheric resistance were a no-go. The craft repeatedly spiralled out of control, control surfaces failed, and reportedly, the inside of the craft became several times hotter than an oven. Fixing these issues would add a tonne of weight, as the front fins would need to be massively reinforced, and the giant heat shield would need to be beefed up significantly. On top of that, these tests confirmed that SpaceX’s engines couldn’t produce the mythical levels of thrust Musk promised, and as such, the projected payload to LEO was cut in half.

To solve the fuel system issues with Block 1, fuel lines with larger internal diameters were needed to increase fuel flow, and larger external walls were needed to increase durability. But this would add an incredible amount of weight that they don’t have the liberty to use, as it would further reduce their already pathetic payload to space and make landing the damn thing even harder than it already is.

As such, SpaceX is having to make the rockets too light, resulting in them being fragile, meaning that just the vibrations from operation with a fraction of its expected payload would be enough to destroy the rocket.

Indeed, we can see this with the planned Block 3 version of Starship. It is even longer than Block 2 to accommodate even more propellant to help increase its shrinking payload and ensure it can slow down enough to land. But somehow, it weighs significantly less than the smaller Block 2.

Where have these weight savings come from? They aren’t changing any major materials. They aren’t changing any structural designs. They aren’t redesigning the entire engine or fuel tank setup. The only way is if major systems are built with a smaller safety factor, making crucial systems vulnerable and weak.

But how did SpaceX get here? Why have they spent billions of dollars of taxpayer money on a concept that has such a fundamental problem?

Simple. Musk isn’t an engineer and doesn’t understand iterative design, and now SpaceX and NASA are facing a sunk cost fallacy.

You never achieve iterative design with a full-scale prototype. It is incredibly wasteful and can lead you down several problematic and dead-end solutions. I used to engineer high-speed boats — another weight- and safety-sensitive engineering field. We would always conduct scale model tests of every aspect of design, iteratively changing it as we went so that when we did build the full-scale version, we were solving the problems of scale, not design and scale simultaneously.

SpaceX could have easily done this. They already proved they could land a 1st stage/Booster with the Falcon 9, and Falcon 9’s Booster could launch a 1/10 scale Starship into orbit. Tests of such a scaled-down model would help SpaceX determine the best compromise for using the bellyflop manoeuvre and retro rockets to land. It would help them iteratively improve the design around such a compromise, especially as they will be far cheaper and quicker to redesign and build than the full-scale versions. Not only that, but these tests would highlight any of the design’s shortcomings, such as the rocket engines not having enough thrust-to-weight ratio to enable a high enough payload. This allows engineers to do crucial, complete redesigns before the large-scale version is even built.

If you have even a passing knowledge of engineering, you know this is what iterative design looks like. So, why hasn’t Musk done this?

Well, developing a Starship like this would expose that making a fully reusable rocket with even a barely usable payload to space is impossible. Musk knows this: Falcon 9 was initially meant to be fully reusable until he discovered that the useful payload would be zero. That was his iterative design telling him Starship was impossible over a decade ago, as just making the rocket larger won’t solve this! But he went on ahead anyway. Why?

Well, through some transparent corruption and cronyism, he could secure multi-billion-dollar contracts from NASA to build this mythical rocket. But, by going for full-scale testing, he could not only hide the inherent flaws of Starship long enough for the cash to be handed over to him but also put NASA in a position of the sunk cost fallacy. NASA has given SpaceX so much money, and their plans rely so heavily on Starship that they can’t walk away; they might as well keep shoving money at the beast.

This is why Starship, in my opinion, is just one massive con.

Ma ei arva et SpaceX insenerid idioodid on. Nad on ilmselt eriala parimad ja teinud ikka uskumatuid asju, nagu näiteks seesamagi boosteri mitmekordne püüdmine. Asjad mida teised kas isegi ei ürita (Euroopa) või on matnud meeletult raha palju sitema tulemusega (Blue Origin j.t.)

Aga seda et Musk nõuab oma maksimalistliku visiooni muutmatul kujul läbisurumist (nagu sellesama Cybertruck'igagi kus insenerid tegid piirides maksimumi, aga piirid olid äärmiselt lollakad) - ning sellest on inseneridel probleemid majas. Vot seda usun küll.

Igatahes siit hakkab tunduma et optimaalsem (kaalu ja kasuliku koorma suhtes) oleks ilmselt natukene väiksem disain ja pole kindel kas selle terviklikul korduvkasutusel oleks tegelikult kuluefektiivest mõtet.

[teeline35]

Minu asjatundmatu arvamus; Kas Maal Marsile ja tagasi lendav osa peaks üldse atmosfääriga planeedile maanduv olema?

[olevtoom]

Minu asjatundmatu arvamus; Kas Maal Marsile ja tagasi lendav osa peaks üldse atmosfääriga planeedile maanduv olema?

Peab ikka. Aeropidurdus aitab kõvasti kütust kokku hoida. (Marss on juhtumisi kah atmosfääriga).

[Lemet]

Minu asjatundmatu arvamus; Kas Maal Marsile ja tagasi lendav osa peaks üldse atmosfääriga planeedile maanduv olema?

Ilmselt ei peaks, atmosfääri siseneda võiks ju ka mingi süstikuga. Aga energia kustutamise probleem jääb ikka, kui tahta, et " Marsilaev" Maa orbiidile jääks ja korduvkasutatav oleks. Ja kütust oleks selleks vaja oi-oi kui palju...sama palju, kui Marsile lendamiseks.

[onu juulius]

Veidi materdavat infot Starshipi kohta. Eks teadjamad oskavad kommenteerida kas päris jama või mitte...

Olen Starshipi arendusel mingil määral silma peal hoidnud, nii et natuke julgen kommenteerida.
Kriitika on osalt õigustatud, osalt märgist mööda ja kohati ka ülekohtune, aga ma olen nõus põhijäreldusega, et Starship kui süsteem võib ka ebaõnnestuda. Ja muidugi et tehniliselt ambitsioonikas eesmärk koos ülemuse põikpäisusega on inseneridele paras peavalu.

Tõsi on see, et mõlema raketiastme tühimass on kavandatust suurem ja kasulik koorem sellevõrra väiksem. Täpsed numbrid ei ole avalikult teada, aga mootorite veojõu ja raketi kiirenduse põhjal saab midagi tuletada. Ja nii on huvilised välja arvutanud, et Starship V2 peaks siiski suutma 80-100 tonni orbiidile viia. SpaceX ise lubab endiselt 100-150 tonni, aga praegu on eesmärgiks pigem alumine number.

Mis puudutab teise (orbitaal-) astme taaskasutust, siis kosmosesüstik ju näitas, et põhimõtteliselt on see võimalik. Ja Starship on samuti suudetud kolmel korral (enamvähem) ühes tükis alla tuua ja pehmelt maandada. Aga teise astme kuumuskaitse probleem ei ole endiselt lahendatud, sest need plaadid kipuvad endiselt purunema ja ära kukkuma, nii et toimivast süsteemist on asi veel kaugel. Kui EM ei oleks nii kõvasti klammerdunud teise astme kohese taaskasutuse külge, siis võiks neil juba praegu olla toimiv üliraskekaalu kanderakett koos võimalusega Starshipi taaskasutust jooksvalt sinna juurde arendada.

SpaceX-i iteratiivse arenduse probleem hetkel näib olevat selles, et nad suudavad rakette kiiremini toota kui katsetada. Kui seitsmenda katsestardi laevuke (S33) lendas ribadeks, siis ei saanud järgmise (S34) konstruktsiooni enam eriti muuta, sest see oli juba valmis ehitatud. Midagi üritati käigu pealt lappida (sest ülemus nõudis järgmist starti), aga nagu selgus, siis ebaõnnestunult. Probleemiks on seal läbi alumise (hapniku) paagi minevad torud, mida mööda metaan ülemisest paagist mootritesse jookseb. Starship V2 juures lisati keskmisele torule vaakum-Raptorite toiteks veel 3 eraldi toru ja need torud ongi nõrk koht. Mootorite turbopumpade suurel kiirusel liikuvad labad tekitavad veeldatud metaanis lööklainete jada, mis liigub mööda vedelikusammast ülespoole ja põhjustab nende toitetorude vibratsiooni. Lennu algfaasis on metaani torud ümbritsetud vedela hapnikuga, mis aitab vibratsiooni summutada, kuid lõpupoole on hapniku nivoo niipalju langenud, et torud jäävad kuivale. Vibratsioon võimendub, mis viib pragude, lekete ja lõpuks tulevärgini. Hetkel ei ole teada, kas nad on sellele probleemile lahenduse leidnud.

[Seto haidamakk]

Siin on huvitav analüüs, mis kattub eelneva postitusega
https://www.youtube.com/watch?v=jhy-FeeO6UU