The most powerful rocket in NASA's inventory is the Space Launch System. When completed, it will weigh 2,875 ton fully fueled, will measure 322 ft (98 m) tall and be able to lift 130 tons into low Earth orbit (LEO). It will be the largest booster ever built and is the key to NASA's ambitions to send crews of up to seven astronauts to cislunar orbit and smaller crews to Mars.
Now picture a spacecraft 200 ft (60 m) tall, weighing around 4,000 ton, and capable of lofting 1,600 ton into LEO along with a crew of eight living in quarters more like that of a small submarine than a cramped capsule. Rather than exotic, lightweight aerospace alloys, the ship's hull is made of welded steel a quarter inch thick using standard submarine-building techniques. In addition, the whole spacecraft is completely reusable and its orbital mission is mere muscle flexing before much bigger things.
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