BFR Refilling | BFR 补给
For refilling, the two ships would actually mate at the rear section. They would use the same mating interface that they used to connect to the booster on liftoff. We would reuse that mating interface and reuse the propellant fill lines that are used when the ship is on the booster. To transfer propellant, it becomes very simple-use control thrusters to accelerate in the direction that you want to empty. If you accelerate in this direction, propellant goes that way, and you transfer the propellant very easily from the tanker to the ship.
补给的时候，两台飞船会在尾部合拢（mate at the rear section）。它们会使用相同的合拢接口，这个接口就是它们发射升空时（liftoff）与助推器连接的接口。除了这个接口，它们还复用连接助推器的推进剂输送管道（propellant fill lines）。转移推进剂非常简单，使用控制推进器（control thruster）往你要输送的方向上怼（accelerate）就可以了。你往哪个方向怼，推进剂就会去往那个方向。这样就很轻松地把推进剂从补给船转移到BFR上。
Rocket Capability | 火箭性能
Figure 8 gives you a rough sense of rocket capability, starting off at the low end with the Falcon 1 at a half-ton and then going up to BFR at 150 tons. I think it is important to note that BFR has more capability than Saturn V even with full reusability. But here is the really important, fundamental point —— let us look at the launch cost.
图8粗略展示了火箭性能的概况（rough sense）。从最左边猎鹰1的半吨到最右边BFR的150吨。必须看到的是BFR不仅比土星5有着更为出色的性能，而且它还是完全可复用的（fully reusability）。但接下来要说的这点才是最惊悚最致命的 —— 发射成本。
When you look at the vehicles against marginal launch cost, the order reverses. I know at first glance this may seem ridiculous but is not. The same is true of aircraft. If you bought a small, single-engine turboprop aircraft —— that would be one and a half to two million dollars. To charter a 747 from California to Australia is half a million dollars, there and back. The single-engine turboprop cannot even get to Australia. So a fully reusable giant aircraft like the 747 costs a third as much as an expendable tiny aircraft.
如果要比较谁的发射费用更少（marginal），那么图8的顺序就要倒过来了。乍听起来好像是扯淡，事实上不是。对于飞机来说也是一样的道理。如果你买了一架小型单引擎涡轮螺旋桨（turboprop）飞机 —— 要花 150 - 200 万美元。如果你租赁（charter）一架波音747客机从加州飞澳洲要花 50 万美元，我指的是往返行程。而单引擎涡轮螺旋桨飞机根本飞不到澳洲。所以使用一架类似747的完全可重用的大型客机只需要花费一次性（expendable）小型飞机1/3的价钱。
In one case you have to build an entire aircraft, in the other case you just have to refuel something. It is really crazy that we build these sophisticated rockets and then crash them every time we fly. This is mad. I cannot emphasize how profound this is and how important reusability is. Often I will be told, but you could get more payload if you made it expendable. "I say yes, you could also get more payload from an aircraft if you got rid of the landing gear and the flaps and just parachute out when you got to your destination. But that would be crazy and you would sell zero aircraft. So reusability is absolutely fundamental.
第一种情况你需要生产一整架飞机，而另一种情况你只需要每次重新加满油即可。
以前我们每次发射都先造出这些先进的（sophisticated）火箭，发射完就炸了它扔海里。这特么真是疯了。我完全无法用言语表达（emphasize）火箭重用（reusability）是一件多么影响深远的（profound）事情。别人常常对我说，如果火箭做成一次性的，就可以装更多的东西。我说，当然啦，你坐飞机时把起落架（landing gear）、襟翼（flaps）、降落伞（parachute）扔掉（get rid of），也可以获得更大的负载空间。但这样的话你将一架飞机也卖不出去。所以重用性绝对是火箭必备的（fundamental）能力。
Value of refilling | 补给的价值
Now I want to talk about the value of orbital refilling. This is also extremely important. If you just fly BFR to orbit and do not do any refilling, it is pretty good-you'll get 150 tons to low Earth orbit, and have no fuel to go anywhere else.
现在我想谈谈在轨补给的价值。这件事也是非常重要的。如果你只是把BFR送上轨道而不提供任何补给，那么好了（it is pretty good） —— 你将把150吨载荷运到近地低轨道，然后再也去不了任何地方。
However, if you send up tankers and refill in orbit, you can refill the tanks all the way to the top and get 150 tons all the way to Mars. And if the tanker has high reuse capability, then you are just paying for the cost of propellant —— the cost of oxygen and the cost of methane is extremely low. If that is all you are dealing with, the cost of refilling your spaceship on orbit is tiny and you can get 150 tons all the way to Mars. So automated rendezvous and docking and refilling are absolutely fundamental.
但是，如果你把补给飞船开上去给BFR在轨加油，油槽加满之后（all the way to the top），就能把150吨载荷一路送到火星上去。如果补给飞船也具备高重用性，那么最后你只是支付了燃油费而已 —— 甲烷和氧气非常廉价。给你的飞船在轨补给是经济实惠的，这样你就可以把150吨载荷开到火星去。所以自动交会对接和在轨补给是BFR必不可少的能力。
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