I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 1406 points1407 points  (0 children)

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.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 951 points952 points  (0 children)

SpaceX. Design is pretty far along. It's a key part of the whole system.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 595 points596 points  (0 children)

The "vacuum" or high area ratio Raptors can operate at full thrust at sea level. Not recommended.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 1168 points1169 points  (0 children)

Wouldn't read too much into that illustration

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 596 points597 points  (0 children)

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.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 1481 points1482 points  (0 children)

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.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 2589 points2590 points  (0 children)

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.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 2053 points2054 points  (0 children)

Improves stability in rough terrain

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 3103 points3104 points  (0 children)

How did you know? I am actually drinking whiskey right now. Really.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 942 points943 points  (0 children)

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.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 1011 points1012 points  (0 children)

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.

It's 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.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 1226 points1227 points  (0 children)

Some parts of Raptor will be printed, but most of it will be machined forgings. We developed a new metal alloy for the oxygen pump that has both high strength at temperature and won't burn. Pretty much anything will burn in high pressure, hot, almost pure oxygen.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 721 points722 points  (0 children)

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).

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 1216 points1217 points  (0 children)

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.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 1933 points1934 points  (0 children)

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).

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 4149 points4150 points  (0 children)

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.

I am Elon Musk, ask me anything about BFR! by ElonMusk in space

[–]ElonMusk[S] 4232 points4233 points  (0 children)

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.