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Elon Musk’s SpaceX AMA: Living on Mars, Spaceship Info, Timeline
SpaceX CEO Elon Musk hosted a Reddit AMA (Ask Me Anything) earlier this afternoon and spent several hours drinking whiskey, trolling the audience, answering some great questions, and generally having a blast. He revealed a vast array of fascinating new details about SpaceX’s giant new rocket (BFR), its upper stage spaceship (BFS), and much more.
All of Musk’s answers from the AMA have been collated and organized by category below. You’ll want to shy away from the AMA page itself, currently clocking in at more 10,000 comments.
When useful, particularly dense and technical responses have been summarized in italics for a broader audience.
Living on Mars
Q: Obviously there will be an extreme amount of care put into what is sent on the first missions, and the obvious answer of “Solar Panels” and “Fuel Production Equipment” is included, but what else?
A (Elon): Our goal is get you there and ensure the basic infrastructure for propellant production and survival is in place. A rough analogy is that we are trying to build the equivalent of the transcontinental railway. A vast amount of industry will need to be built on Mars by many other companies and millions of people.
Q: Does your Mars city feature permanently anchored BFS spaceships?
A (Elon): Wouldn’t read too much into that illustration
The aforementioned Martian city. Spaceships can be seen near the center. (SpaceX)
Q: Have any candidate landing sites for the Mars base been identified?
A (Elon): Landing site needs to be low altitude to maximize aero braking, be close to ice for propellant production and not have giant boulders. Closer to the equator is better too for solar power production and not freezing your ass off.
Q: Who will design and build the ISRU system for the propellant depot, and how far along is it?
A (Elon): SpaceX. Design is pretty far along. It’s a key part of the whole system.
Without ISRU (In-Situ Resource Utilization), BFS is unlikely to ever be able to take humans to Mars affordably enough to enable large colonies. This news is thus of huge importance, and suggests that SpaceX will be able to focus on developing BFR and BFS near-term.
Another hypothetical SpaceX city on Mars. Bases will need to be located near water resources. (SpaceX)
SpaceX Big F** Spaceship (BFS)
Q: Will the BFS landing propellants have to be actively cooled on the long trip to Mars?
A (Elon): The main tanks will be vented to vacuum, the outside of the ship is well insulated (primarily for reentry heating) and the nose of the ship will be pointed mostly towards the sun, so very little heat is expected to reach the header tanks. That said, the propellant can be cooled either with a small amount of evaporation. Down the road, we might add a cryocooler.
A (Elon): exactly (while methane could be kept in its liquid form solely through high pressure storage, the pressures required are immense and would require tanks that would be far too heavy for a rocket’s second stage.
Cold liquid oxygen and methane will unavoidably warm up over time, eventually returning to their gaseous forms if allowed. SpaceX’s solution for BFS, which will spend several months between Earth and Mars, is to rely on the Ship’s already great insulation, as well as minimal evaporative cooling (similar to how swamp coolers work).
Q: Will the BFS heat shield be mounted on the skin, or embedded?
A (Elon): The heat shield plates will be mounted directly to the primary tank wall. That’s the most mass efficient way to go. Don’t want to build a box in box.
Dragon 2’s PICA-X heat shield can be seen on the right. BFS’s heat shield will be made of the same material, albeit on a much larger scale. (SpaceX)
Q: Can the BFS delta wings and heat shield be removed for deep space missions?
A (Elon): Wouldn’t call what BFS has a delta wing. It is quite small (and light) relative to the rest of the vehicle and is never actually used to generate lift in the way that an aircraft wing is used.
Its true purpose is to “balance out” the ship, ensuring that it doesn’t enter engines first from orbit (that would be really bad), and provide pitch and yaw control during reentry.
Q: Why is the 2017 BFS spaceship largely cylindrical?
A (Elon): Best mass ratio is achieved by not building a box in a box. The propellant tanks need to be cylindrical to be remotely mass efficient and they have to carry ascent load, so lowest mass solution is just to mount the heat shield plates directly to the tank wall.
For a rocket, mass ratio refers to its weight with a full load of propellant divided by its weight while completely empty. The lighter a rocket’s structure, the more mass it can lift into a given orbit.
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- SpaceX’s conceptual Interplanetary Transport System from 2016 was considerably larger and more structurally complex than 2017’s BFR. (SpaceX)
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- The relatively cylindrical BFS reduces complexity and lowers weight. (SpaceX)
Q: How does the BFS achieve vertical stabilization, without a tail?
A (Elon): Tails are lame
A (Elon): +1 (The space shuttle’s vertical stabilizer was completely useless for most of the reentry profile, as it was in complete aerodynamic shadow. I think it’s clear a craft doesn’t need one for reentry, only for subsonic gliding, which BFS doesn’t really do.)
BFS doesn’t need a tail because tails add weight, are of little use during orbital reentry, and BFS is not intended to glide.
Q: Why was the number of BFS landing legs increased from 3 to 4?
A (Elon): Because 4
A (Elon): Improves stability in rough terrain
Q: How is the radiation shielding in the ITS?
A (Elon): Ambient radiation damage is not significant for our transit times. Just need a solar storm shelter, which is a small part of the ship. Buzz Aldrin is 87.
While radiation fearmongers may balk at this statement, it is to some extent true. The risks from radiation (PDF) for a six month journey in deep space are approximately similar to several dozen CT scans, while two years spent on the surface of Mars with little to no shielding would result in about the same amount of exposure. Underground habitats could alleviate a considerable amount of the risk from living on Mars’ surface.
The issues and dangers posed by radiation ought not be trivialized but they can be dealt with, particularly if BFR can deliver massive payloads to the planet.
Q: Why was the location and shape of the BFS header/landing tanks changed?
A (Elon): The aspiration by the change was to avoid/minimize plumbing hell, but we don’t super love the current header tank/plumbing design. Further refinement is likely.
Header tanks refer to smaller tanks contained within the main propellant tanks that are used to ignite engines in microgravity. It’s easier to pressurize or simply fill the smaller tanks than it is to do so with the massive main tanks.
BFS’ header tanks circled in red. (SpaceX)
BFS Tanker
Q: Will the BFS tanker’s payload section be empty, or include extra propellant tanks?
A (Elon): At first, the tanker will just be a ship with no payload. Down the road, we will build a dedicated tanker that will have an extremely high full to empty mass ratio (warning: it will look kinda weird).
Using one version of the BFS as both a tanker and ship will streamline the initial development process for the rocket.
Two Spaceships docked for refuelling. (SpaceX)
Q: Will the BFS tanker ships (have to) do a hoverslam landing?
A (Elon): Landing will not be a hoverslam, depending on what you mean by the “slam” part. Thrust to weight of 1.3 will feel quite gentle. The tanker will only feel the 0.3 part, as gravity cancels out the 1. Launch is also around 1.3 T/W, so it will look pretty much like a launch in reverse….
BFS will land relatively gently, and BFR’s liftoff will also be gentle.
Development schedule
Q: With the first two cargo missions scheduled to land on Mars in 2022, what kind of development progress can we expect to see from SpaceX in the next 5 or so years leading up to the maiden flight?
Will we see BFS hops or smaller test vehicles similar to Grasshopper/F9R-Dev? Facilities being built? Propellant plant testing? etc. etc.
A (Elon): A lot. Yes, yes, and yes.
A (Elon): Will be starting with a full-scale Ship doing short hops of a few hundred kilometers altitude and lateral distance. Those are fairly easy on the vehicle, as no heat shield is needed, we can have a large amount of reserve propellant and don’t need the high area ratio, deep space Raptor engines.
Next step will be doing orbital velocity Ship flights, which will need all of the above. Worth noting that BFS is capable of reaching orbit by itself with low payload, but having the BF Booster increases payload by more than an order of magnitude. Earth is the wrong planet for single stage to orbit. No problemo on Mars.
The first real tests of the BFR will be done by hopping a full-scale BFS “several hundred kilometers”. BFS is capable of launching itself and a tiny payload into orbit, but the utility is limited on Earth. On Mars, BFS will be far more capable as a single stage to orbit (SSTO) launch vehicle.
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- F9R-dev, used to test vertical take off and landing for Falcon 9. BFR will go through a similar program with its spaceship upper stage prior to orbital missions. (Steve Jurvetson)
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- F9R sadly suffered a software bug and self-destructed in 2014, but SpaceX had already learned most of what it needed to begin Falcon 9 recoveries. (Steve Jurvetson)
Raptor and rocket propulsion
Q: Why was Raptor thrust reduced from ~300 tons-force to ~170 tons-force?
A (Elon): We chickened out. The engine thrust dropped roughly in proportion to the vehicle mass reduction from the first IAC talk. In order to be able to land the BF Ship with an engine failure at the worst possible moment, you have to have multiple engines. The difficulty of deep throttling an engine increases in a non-linear way, so 2:1 is fairly easy, but a deep 5:1 is very hard. Granularity is also a big factor. If you just have two engines that do everything, the engine complexity is much higher and, if one fails, you’ve lost half your power. Btw, we modified the BFS design since IAC to add a third medium area ratio Raptor engine partly for that reason (lose only 1/3 thrust in engine out) and allow landings with higher payload mass for the Earth to Earth transport function.
The Raptor engine’s maximum thrust has been decreased mainly because the size of the rocket decreased, from 12m to 9m in diameter. For redundancy’s sake, SpaceX has added a third central engine to the spaceship, versus the two engines mentioned at the 2017 IAC.
BFS’ delta “wings” from the rear of the ship. Also shown are the Raptors, with the two in the center now reportedly expanded to three engines. (SpaceX)
Q: Will the BFR autogenous pressurization system be heat exchanger based?
A (Elon): We plan to use the Incendio spell from Harry Potter
A (Elon): But, yes and probably
Autogenous pressurization refers to the method of propellant tank pressurization used. In microgravity conditions, tanks must be pressurized to keep fuel flowing to the engines and to improve the density of the fuel. While Falcon 9 currently uses high-pressure helium, ITS and now BFR have been designed to use the actual propellant in their tanks (methane and oxygen) for pressurization. This reduces the number of failure modes on BFR and improves the spaceship’s payload capabilities.
Q: Will the BFS methalox control thrusters be derived from Raptor or from SuperDraco engines?
A (Elon): The control thrusters will be closer in design to the Raptor main chamber than SuperDraco and will be pressure-fed to enable lowest possible impulse bit (no turbopump spin delay).
Like Falcon 9, BFR will need gas thrusters (RCS, reaction control system) to control its orientation (and refuel) while in microgravity conditions. While Falcon uses cold nitrogen gas thrusters, BFR will utilize the propellant it is already carrying for Raptor, methane and oxygen. Again, the goal of this is to reduce complexity.
Q: Could you update us on the status of scaling up the Raptor prototype to the final size?
A (Elon): Thrust scaling is the easy part. Very simple to scale the dev Raptor to 170 tons.
The flight engine design is much lighter and tighter, and is extremely focused on reliability. The objective is to meet or exceed passenger airline levels of safety. If our engine is even close to a jet engine in reliability, has a flak shield to protect against a rapid unscheduled disassembly and we have more engines than the typical two of most airliners, then exceeding airline safety should be possible.
That will be especially important for point to point journeys on Earth. The advantage of getting somewhere in 30 mins by rocket instead of 15 hours by plane will be negatively affected if “but also, you might die” is on the ticket.
SpaceX’s subscale Raptor, the one seen in videos and photos of it firing, is understood to be a bit more than half the size of the operational engine described at IAC 2017. Increasing the scale of the engine is not the difficult aspect of development. Rather, optimization, weight reduction, and extreme reusability are the main sources of difficulty needed before Raptor is flight-ready. This reusability is central to the goal of reliable and rapid reuse of orbital-class rockets.
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- SpaceX revealed this stunning photo of Raptor’s first (partial) hot-fire test the night before Musk’s talk at Guadalajara. (SpaceX)
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- SpaceX’s subscale Raptor engine has completed more than 1200 seconds of testing in less than two years. (SpaceX)
Q: Can BFS vacuum-Raptors be fired at sea level pressure?
A: The “vacuum” or high area ratio Raptors can operate at full thrust at sea level. Not recommended.
Put simply, vacuum nozzles do not like to operate in an atmosphere.
Mars communications
Q: Does SpaceX have any interest in putting more satellites in orbit around Mars (or even rockets) for internet/communications before we get feet on the ground? Or are the current 5-6 active ones we have there sufficient?
A (Elon): Yes
Q: Also will there be some form of an internet or communications link with Earth? Is SpaceX going to be in charge of putting this in or are you contracting some other companies?
A (Elon): If anyone wants to build a high bandwidth comm link to Mars, please do.
Taken side by side, this likely indicates that SpaceX will develop a high-bandwidth Mars-Earth communications link if nobody else does, but that they would logical prefer that someone else builds that infrastructure beforehand.
Q: The concept of an internet connection on Mars is kinda awesome. You could theoretically make an internet protocol that would mirror a subset of the internet near Mars. A user would need to queue up the parts of the internet they wanted available and the servers would sync the relevant data.
A (Elon): Nerd
A (Elon): But, yes, it would make sense to strip the headers out and do a UDP-style feed with extreme compression and a CRC check to confirm the packet is good, then do a batch resend of the CRC-failed packets. Something like that. Earth to Mars is over 22 light-minutes at max distance.
A (Elon): 3 light-minutes at closest distance. So you could Snapchat, I suppose. If that’s a thing in the future.
The communication delay between Earth and Mars (at least several minutes one-way) will prevent any Martian habitats from simply integrating with Earth’s Internet. The delay will require some sort of mediation. As an example, a user on Mars could select the websites they want to browse or videos they want to watch beforehand, and they would be available between several minutes and an hour later.
SpaceX’s Starlink satellite constellation efforts could provide the company with valuable experience that can be applied around Mars. (unofficial logo by Eric Ralph)
Boring!
Q: Boring question about Mars:
A (Elon): More boring!
Miscellaneous silliness
Q: This is one bizarre AMA so far…
A (Elon): Just wait…
Q: i feel like thats a threat. “just wait. it will get way more bizarre than that. let me finish my whiskey”
A (Elon): How did you know? I am actually drinking whiskey right now. Really.
…No comment…
All things considered, this was a wildly successful AMA. Elon clearly had a whole lot of fun, the audience got lightheartedly trolled, and SpaceX fans will undoubtedly be chewing over the technical details he elucidated for weeks to come. Special thanks are owed to the subreddit /r/SpaceX and user /u/_Rocket_, who together managed to flood the AMA with an array of intelligent, pointed, and reasonable questions, at least ten of which were answered by Musk.
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Tesla Cybercabs take over Austin’s F1 weekend
Tesla Cybercabs swarmed Austin’s F1 Grand Prix as sightings hit a record during race weekend.
Tesla’s driverless Cybercabs used the Formula 1 United States Grand Prix in Austin as their biggest public stress test yet. On Sunday afternoon, Tesla head of AI software Ashok Elluswamy quoted a photo from X user Ben Steindl showing a long line of gold Cybercabs and Model Y Robotaxis stacked up on a road near Circuit of the Americas. “Robotaxis as far as the eye can see!” Elluswamy wrote. Steindl’s original post was more matter of fact: “@Tesla @robotaxi is busy for the Austin F1.”
The fleet also handled the trip home. The race started at 3 p.m. Central, and once it ended, Cybercab Spotter, an account that logs Cybercab sightings around Austin, posted that “People are requesting Cybercabs to get home.”
Robotaxis as far as the eye can see! 🤩
— Ashok Elluswamy (@aelluswamy) October 25, 2026
Tesla set this up days in advance without announcing it. Late on October 22, rider David Moss posted Robotaxi app screenshots showing the Austin service area wrapping around the track toward Elroy and FM 812, with ride requests open until 1 a.m. A banner in the app read “Last call is 1am · Limited to nearby dropoffs.” Austin rides ended at 11 p.m. as recently as early October, as Teslarati reported, before moving to midnight on October 17.
Not every rider got dropped at the gate. Early app searches showed spots like COTA Karting as “Service blocked,” and one rider who took a Cybercab to the track Friday said the rideshare area was less than a 20 minute walk from the front gate.
The weekend also produced a new activity record. Cybercab Spotter counted 1,250 Cybercab sightings in Austin on Saturday, qualifying day. The previous high was 1,072 on October 16. Sightings count the same car more than once, so they measure how busy the fleet is rather than how big it is. For size, the Texas automated vehicle registry listed 463 Cybercabs at midday Sunday, up from the 300+ Tesla claimed on October 10, when Elluswamy also said Dallas is next for Cybercab.
The track was out of reach for Tesla’s main rival. Waymo runs in Austin only through Uber, and its service area stops well short of COTA. Waymo did not announce any race day service.
Tesla has not said how many rides it gave to and from the circuit, or whether the expanded zone and 1 a.m. cutoff will stay after race weekend. On the third quarter earnings call, Elluswamy said 2 a.m. service is coming “pretty soon” and that Tesla plans to run Robotaxi around the clock before the end of the year. The company is also aiming to hand the first Cybercabs to customers before 2026 ends, which would put cars like these outside Tesla’s own fleet for the first time.
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Tesla makes good on its Cybercab promise in just two weeks
Tesla Cybercab riders can now pull up a rear camera view and darken the screen.
Tesla has given Cybercab passengers a way to see what is behind them, along with a way to turn the cabin screen off entirely.
Riders in Austin can now bring up a live rearview camera feed on the Cybercab’s center display in the middle of a trip. Austin rider Ethan McKanna spotted the change late Friday night, posting from a ride that “You can now open the camera to view what’s behind you in Cybercab!” His photo shows a strip of rear camera video across the top of the screen, with another Cybercab following on a bridge. Sawyer Merritt shared the image Saturday and wrote that it “sounds like” there is also a new quiet mode that darkens the entire screen for riders who want to relax, sleep, or avoid a bright display at night.
The camera view goes beyond the rear feed. Tesla UI software engineer Evan, who posts as @CarCoder, replied to McKanna with a tip: “You can also tap it to see more cameras, and swipe it up or down to hide and show.” Until now, the Cybercab only showed its rear and repeater feeds on the “Please Exit Safely” screen at the end of a ride, so passengers could check for cyclists and traffic before opening a door.
Quiet mode surfaced a day earlier. Austin rider Jackson Blatz posted a video Friday morning of the new Robotaxi interface in a Cybercab with the option. Tesla has not published release notes for either feature.
The rear camera view moved quickly from request to release. Earlier this month, Cybercab rider Dan Burkland asked Tesla to let passengers pull up the rear and repeater cameras whenever they want, “especially for peace of mind.” Evan answered “In development,” as Teslarati reported at the time. About two weeks later, riders have it.
The feature fills a gap created by the Cybercab’s design. With no steering wheel, no pedals, no mirrors and no rear window, a passenger has no natural way to glance behind the car. The eight exterior cameras that feed Tesla’s autonomy software were already on board, so the change only required software.
There is also an AI angle to how it was built. Yun-Ta Tsai, a senior staff engineer on Tesla’s AI team, quoted Merritt’s post and wrote that the “(human) camera view tuning is optimized with Grok and implements part of the algorithm by directly programming the fixed-function hardware, so I don’t even need to check the datasheet.” Tsai did not say which part of the algorithm Grok handled. Grok already plays a bigger role inside the vehicle, with Grok Bot now enabled across every Cybercab and the Model Y Robotaxi fleet after Tesla brought the agent into its cars in September.
The two features join a busy week of changes for riders in Austin, which also brought a redesigned Live Activity for iPhone and Apple Watch and live trip sharing. They also arrive as Tesla prepares the Cybercab for life outside its own fleet. On the third quarter earnings call, Lars Moravy said the company is aiming to deliver Cybercabs to customers before the end of 2026. Tesla has not said whether the camera view and quiet mode will also come to its Model Y Robotaxis.
Elon Musk
Tesla shows what Roadster drivers will see on screen before thruster activation
Tesla’s Roadster video reveals a fighter jet inspired cockpit with a 5,500 PSI thruster gauge.
Tesla has given future owners their clearest look yet at the cockpit of its next generation Roadster. In a 34 second video posted to X on Friday afternoon, the company walked through the car’s touchscreen with a caption: “Inspired by fighter jet cockpits, Roadster’s interface was designed around the pilot.”
The clip opens on a black screen with red graphics and a 3D wireframe of the car, which sits beside the Roadster’s squared off yoke. Tapping parts of the model brings up controls for the rear wing, including low drag and high downforce positions, along with a charging page with a charge limit bar and a small music player. A row of tabs along the bottom reads Home, Vehicle, Listen, Climate and Navigate.
Most of the video is spent in Track Mode. The dashboard shows a live circuit map, a list of session lap times, brake and motor temperatures, and pressure and temperature readouts for each tire. A setup page lets the driver pick Auto, Low Drag, High Downforce or Custom aero modes, adjust aero balance and brake balance, and switch stability and traction control off. Along the bottom, a status bar reads “Thruster · 5,500 PSI” next to a “Boost Ready” indicator.
That gauge ties the software to the hardware Tesla showed off near Waco, Texas on October 15. The Thrust and Rocket versions use cold gas thrusters fed by carbon overwrapped pressure vessels, and Tesla lists 0 to 60 mph times of under 0.9 seconds and under 0.59 seconds for them, as Teslarati detailed in its breakdown of the three Roadster configurations. The base Performance car relies on a fan and ground sealing system for grip, and the aero settings on screen match the active wings and suction setup covered in our look at how the Roadster generates downforce.
The Roadster layout is a departure from the rest of Tesla’s lineup. Instead of a map centered screen, the Roadster puts the car itself at the center of the home page, and Tesla’s Roadster page lists two smaller forward displays alongside the main touchscreen. Tesla has not said whether any of the Track Mode telemetry will make its way to the Model 3 Performance or other vehicles.
The interface could still change before deliveries. Elon Musk said at the event that Roadster production will begin in 2028, and Tesla says the flagship Rocket version is not approved for public road use. Reservations are open with a $50,000 payment, while Thrust is listed as a limited release and Rocket is invite only.
Those who want to see the car in person will get their first chance this weekend. The Roadster goes on display in the lobby of the Petersen Automotive Museum in Los Angeles from October 24 to 27, according to Sawyer Merritt, the first time the public will be able to view it up close.
Tesla Cybercabs take over Austin’s F1 weekend
Tesla makes good on its Cybercab promise in just two weeks
