The tweet archive.

“Pluto takes 248 years to orbit the sun, but Uranus only takes 84”

“@BryceSpaceTech Useful mass to orbit is the primary figure of merit”

“@skorusARK Exactly. Atmospheric drag clearing out orbital debris is a major reason why we dropped altitude to ~550km.”

“@SciGuySpace Cumulative payload to orbit is the really crazy number. Falcon has delivered more than double rest of world combined over trailing 12 months.”

“@Astro_Elliott @Teslarati @ResidentSponge Aiming to have hot gas thrusters on booster for first orbital flight”

“@nextspaceflight @NASASpaceflight Only way to create rapidly & fully reusable orbital rockets, the fundamental technology revolution needed to make life multiplanetary”

“@kchangnyt Can’t get it up (to orbit) lol”

“@SciGuySpace Global payload to orbit is the key metric”

“@Adamklotz_ @SpaceX BN1 is a manufacturing pathfinder, so will be scrapped. We learned a lot, but have already changed design to BN2. Goal is to get BN2 with engines on orbital pad before end of April. It might even be orbit-capable if we are lucky.”

“@Adamklotz_ @SpaceX Next major technology rev is at SN20. Those ships will be orbit-capable with heat shield & stage separation system. Ascent success probability is high. However, SN20+ vehicles will probably need many flight attempts to survive Mach 25 entry heating & land intact.”

“@SpacexVision An orbital propellant depot optimized for cryogenic storage probably makes sense long-term”

“@SciGuySpace SpaceX did 2X rest of world payload to orbit last year, probably 3X to 4X this year”

“@PPathole @arstechnica @SciGuySpace If 2021 manifest is met, SpaceX will do ~75% of total Earth payload to orbit with Falcon. A single Starship is designed to do in a day what all rockets on Earth currently do in a year. Even so, ~1000 Starships will take ~20 years to build a self-sustaining city on Mars.”

“@arstechnica @SciGuySpace Falcon 9 is almost always at max capacity. When it has “spare” performance, it flies back to land, which costs much less than using a droneship. Our fundamental constraint is mass to orbit per unit time. Last year, SpaceX launched roughly double payload mass of rest of world.”

“@Erdayastronaut @michaelhodapp_ 1. Orbital launch tower that can stack 2. Enough Raptors for orbit booster 3. Improve ship & booster mass”

“Launching many small satellites for a wide range of customers tomorrow. Excited about offering low-cost access to orbit for small companies!”

“@Virgin_Orbit Congratulations!”

“@engineers_feed Not to get to orbit, unfortunately. In space, photon emission powered by matter-antimatter annihilation would rock, but that’s more of a long-term solution.”

“@spacecoast_stve @NASASpaceflight Falcon was 25% of successful orbital launches in 2020, but maybe a majority of payload to orbit. Anyone done the math?”

“@wonderofscience Near-orbital space is the fastest way to travel long distance on Earth!”

“@MarcusHouseGame Rapid & complete rocket reuse, low cost propellant, orbital refilling & propellant production at destination are the four essential elements of making life multiplanetary”

“@peterrhague It’s designed to make life multiplanetary, otherwise extreme overkill for mere Earth sector activity! Starship fleet mass to orbit per year will be more than 1000 times all current Earth rockets combined, including Falcon. Necessary, for a city on Mars.”

“@PPathole @Erdayastronaut @rweb11742 Yeah, looks like marginal cost of launch will be less than $1M for more than 100 tons to orbit, so it’s mostly about fixed costs divided by launches per year”

“The same propellant is used either for abort or for orbital maneuvering, as one use obviates the other”

“@Erdayastronaut After it gets to orbit a few times”

“@Erdayastronaut Those engines could go 300 bar, but would be dicey. Pushing it for near-term tests doesn’t achieve anything, but I’m confident Raptor will do 300 bar for orbital flights.”

“@skorusARK Marginal cost of Starship mass to orbit should be well under $100/kg. Fully burdened cost depends on flight rate.”

“@SciGuySpace It’s a step in the right direction, but they should really aim for full reusability by 2026. Larger rocket would also make sense for literal economies of scale. Goal should be to minimize cost per useful ton to orbit or it will at best serve a niche market.”

“@tobyliiiiiiiiii @RationalEtienne @SPEXcast @William_M_Brown @PPathole @thesheetztweetz @waEMD @SpaceX @SpaceXStarlink @WANationalGuard Oh yeah, Starship update coming in about 3 weeks. The design has coalesced. What is presented will actually be what flies to orbit as V1.0 with almost no changes.”

“@PPathole @Erdayastronaut @NASASpaceflight @BocaChicaGal @TheFavoritist Probably 5 or 6 with an optimized tanker, although filling up the ship in orbit isn’t required for Mars, so 4 is possible”

“@MatthewCable6 @ErcXspace Just a guess, but probably mid teens. Booster & stacking on orbital pad are likely limiting factors. We’ll build several ships just to improve the production system.”

“@PPathole @_rykllan @FelixSchlang @spaceXcentric @MarcusHouseGame @SpaceX Cumulative mass to orbit per year (corrected for GTO & other high energy orbits) is the best comparative metric imo”

“@_rykllan @FelixSchlang @spaceXcentric @MarcusHouseGame @SpaceX Anyone tracking tonnage to orbit per year for all launch vehicles?”

“@Astra Sorry to hear that. I’m sure you’ll figure it out though. Took us four launches to reach orbit. Rockets are hard.”

“@Erdayastronaut @dauqhx @universal_sci Starship propellant is ~78% oxygen, so an O2 plant on the moon would be enough. Otherwise, we could brute-force it with tankers to low Earth orbit. That’s probably faster.”

“@Erdayastronaut Orbital launch mount”

“@Erdayastronaut @C_Bass3d @NASASpaceflight @FelixSchlang It’s counter-intuitive, but Raptor has so much thrust at high Isp with liquid (high density) propellant & pump-fed (light tanks), that it beats hot gas for the flip. That said, hot gas beats the heck out of N2 for orbital manuevers & stabilizing ship if landing in high winds!”

“@Erdayastronaut @thesheetztweetz @BryceSpaceTech @SpaceX @ulalaunch @torybruno @MHI_Group @roscosmos @Peter_J_Beck To revolutionize space, the right metric is mass to orbit or you could translate that to # of useful satellites brought to orbit. No substitute for mass though. Scale don’t lie.”

“@RocketLab Sorry to hear about this. Hope you get back to orbit soon. Rockets are hard.”

“@Virgin_Orbit Sorry to hear that. Orbit is hard. Took us four attempts with Falcon 1.”

“@JonErlichman 5 years ago. We need to accelerate progress towards fully reusable rockets. Cost per ton to orbit needs to improve by >1000% from where Falcon is today for there to be a self-sustaining city on Mars.”

“@SpaceX Astronauts to orbit in 5 days!!”

“@Erdayastronaut @SpaceX @NASA @Astro_Doug @AstroBehnken Astronauts to orbit next week!”

“@flcnhvy @Erdayastronaut @ValkyrieBaron11 @NASASpaceflight Starship + Super Heavy propellant mass is 4800 tons (78% O2 & 22% CH4). I think we can get propellant cost down to ~$100/ton in volume, so ~$500k/flight. With high flight rate, probably below $1.5M fully burdened cost for 150 tons to orbit or ~$10/kg.”

“@Erdayastronaut @ValkyrieBaron11 @flcnhvy @NASASpaceflight A fully & rapidly reusable orbital rocket is fundamental to extending life beyond Earth. Propellant cost is roughly a 1000th of vehicle cost (unless using a foolish propellant). Same principle as cars, planes, boats, etc.”

“@Erdayastronaut @flcnhvy @anime_virus @thirdrowtesla @MFrunker Solar panel angle during orbit raise / park. We’re fixing it now.”

“@thirdrowtesla @MFrunker Thanks! We are taking some key steps to reduce satellite brightness btw. Should be much less noticeable during orbit raise by changing solar panel angle & all sats get sunshades starting with launch 9.”

“@Erdayastronaut @teslaownersSV @NASA SpaceX has a lot of experience berthing & now docking with @Space_Station, which is very difficult. Orbital refilling should in theory be easier, since Starships dock with themselves & will be uncrewed at first.”

“@teslaownersSV @Erdayastronaut Fully reusable orbital rocket, then orbital refilling, then Mars”

“Orbital human spaceflight returns to the Cape in six weeks!”