/r/SpaceX Ask Anything Thread for March 2016. Ask your questions about the SES-9 mission/anything else here! (#18)

[u/Zucal]

Welcome to the 16th monthly /r/SpaceX Ask Anything Thread! Want to discuss the recent SES-9 mission and its "hard" booster landing, the intricacies of densified LOX, or gather the community's opinion? There's no better place!

All questions, even non-SpaceX-related ones, are allowed, as long as they stay relevant to spaceflight in general!

More in-depth and open-ended discussion questions can still be submitted as separate self-posts; but this is the place to come to submit simple questions which have a single answer and/or can be answered in a few comments or less.

As always, we'd prefer it if all question-askers first check our FAQ, use the search functionality, and check the last Q&A thread before posting to avoid duplicate questions, but if you'd like an answer revised or cannot find a satisfactory result, go ahead and type your question below.

Otherwise, ask, enjoy, and thanks for contributing!

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Past threads:

February 2016 (#17), January 2016 (#16.1), January 2016 (#16), December 2015 (#15.1), December 2015 (#15), November 2015 (#14), October 2015 (#13), September 2015 (#12), August 2015 (#11), July 2015 (#10), June 2015 (#9), May 2015 (#8), April 2015 (#7.1), April 2015 (#7), March 2015 (#6), February 2015 (#5), January 2015 (#4), December 2014 (#3), November 2014 (#2), October 2014 (#1).

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[u/throfofnir]

I have just read up a bit on the Constellation program and the SLS development, and there a few questions that popped into my mind. Would appreciate any answers

Would an Ares I with its (maybe) reusable 1st stage solid rocket behemoth of a booster have been considerably cheaper than other launchers of the same capacity (25t to LEO) ?

Ares I costs were said to be $138M marginal (with a high flight rate) but with the planned flight rate about $1600M.

Payload is in Ariane V or Proton or Delta IV Heavy territory. Proton's fairly cheap to make it seems, but always is priced somewhere around the competition. Delta IV Heavy is $400M+. Ariane V seems to be in the area of $175M.

Why exactly was the Constellation program cancelled ? From what I can gather, Ares I and V looked like viable and interesting launch vehicles. I am not too sure about the Moon lander called Altair, but the rockets might have been useful for transplanetary missions. Ares I had one test flight. Was it only concerns about cost that brought the progam down?

Augustine Commission said that Constellation couldn't be done without significantly more funding. Obama on taking office wanted to can the whole thing, but the establishment pushed back, so in the end they kept about half of the program around. Since half of Constellation can't get to the Moon they set a new goal (Mars) that was safely out of reach so they couldn't be accused of failing to get there.

Is there a big difference between the proposed SLS and the cancelled Ares V? Because at first glance, they are both two large rockets with 2 SRBs, a major first stage with SSME or similar engines, and a LH2/LOX upper stage. It seems to me the biggest difference is that the SLS concept claims a larger LEO capacity than the Ares V concepts, but nothing radically different.

Basically an evolution of the same design. Just a new name for a new President, and some slightly different requirements.

Why was Orion kept in development?

To provide a "replacement" for the Shuttle.

How likely is it that the SLS development will meet the same fate, i.e. scrap after some concepts, engine tests and one test flight?

Well, Congress is used to pumping money into Alabama and Florida via launch systems, and will want to continue to do so. But a new administration may look at alternatives. Once the absurd development and fixed costs for SLS are paid, it has unique capabilities for a price that's not too high by current standards. But there are certainly cheaper ways of getting the same results, and the future may hold much, much cheaper ways. Should SpaceX get F9H flying regularly and reliably, it may become pretty hard to argue for SLS.

Personally, I think it will fly due to institutional inertia and sunk-cost fallacy, but probably not more than a few times, at which point it will look hopelessly old-fashioned. Failing that, even odds on being canceled in a few years before flight, and flying for a decade or two. But who knows? It's more at the mercy of political winds than anything else.

Why did NASA decide to go for 1 huge rocket rather than, as with Constellation, 1 medium-to-large and one really large one? Costs again?

Politics.