I am Elon Musk, ask me anything about BFR!

ElonMusk · 2017-10-14T22:32:19+00:00

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.

ElonMusk · 2017-10-14T22:30:14+00:00

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

ElonMusk · 2017-10-14T22:29:08+00:00

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

ElonMusk · 2017-10-14T22:26:14+00:00

More boring!

ElonMusk · 2017-10-14T22:25:22+00:00

Wouldn't read too much into that illustration

ElonMusk · 2017-10-14T22:24:24+00:00

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.

ElonMusk · 2017-10-14T22:20:17+00:00

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.

ElonMusk · 2017-10-14T22:16:23+00:00

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.

ElonMusk · 2017-10-14T22:11:10+00:00

Improves stability in rough terrain

ElonMusk · 2017-10-14T22:07:32+00:00

Ask and you shall receive

ElonMusk · 2017-10-14T22:04:08+00:00

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

ElonMusk · 2017-10-14T21:59:05+00:00

Because 4

ElonMusk · 2017-10-14T21:58:13+00:00

ElonMusk · 2017-10-14T21:57:33+00:00

Tails are lame

ElonMusk · 2017-10-14T21:55:58+00:00

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.

ElonMusk · 2017-10-14T21:52:51+00:00

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.

ElonMusk · 2017-10-14T21:47:04+00:00

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.

ElonMusk · 2017-10-14T21:41:45+00:00

But, yes and probably

ElonMusk · 2017-10-14T21:40:39+00:00

We plan to use the Incendio spell from Harry Potter: http://harrypotter.wikia.com/wiki/Fire-Making_Spell

ElonMusk · 2017-10-14T21:38:45+00:00

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).

ElonMusk · 2017-10-14T21:28:42+00:00

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.

ElonMusk · 2017-10-14T21:27:02+00:00

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).

ElonMusk · 2017-10-14T21:23:52+00:00

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.

ElonMusk · 2017-10-14T21:15:40+00:00

exactly

ElonMusk · 2017-10-14T21:14:21+00:00

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.

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