Here’s what you need to know about SLS

What I do know is that SLS is certain to get delayed again. By 2025 we will have paid close to $50 billion for SLS and Orion, and the best we can hope for is a single manned mission. And that one mission will have taken 21 years to go from concept to launch.

Ye gods.

Elon Musk is – probably optimistically – suggesting that the even-more-capable BFR will not only fly before 2025, not only fly people before 2025, but will fly people to *Mars* by 2025. BFR began development approximately 2012, and prototype bits of it are hoped to fly next year. BFR is an all-new giant vehicle using all-new engines and structures. SLS is a kludge of the 1970’s-vintage Shuttle external tank, main engines and solid rocket boosters with an upper stage derived from Delta and Centaur, launching from an existing but modified facility. NASA *should* have been able to slap SLS together in a handful of years.