And I'm going to point out, (again

) that you don't have chemical and Orion's competing in any scenario. You HAVE to have both since you can't land an Orion efficiently, (note that last word because while you CAN in theory land an Orion in the ocean the fine control needed wasn't available at the time AND it is only usable on Earth, every other destination is going to have a very large spot of high radiation and slag where the Orion touches down, not conducive to surface operations, and worse is that the mechanical pressures of landing on the pusher plate is VASTLY different than the shock mechanics of the drive itself and would definitely damage the pusher plate severely

) and you need chemical rocket propelled supplies and personnel to service the Orion's on-orbit. The designers, (especially but most proponents as well) tended to gloss over the whole issue of landing and surface operations but the fact is the Orion IS a brute force system that gets a lot of payload, (and structural mass) into space and from place to place but it's really, really bad at fine maneuvers or getting stuff from space to the surface.
And speaking of; Sea Dragon, was a TSTO "big-dumb-booster" which used RP-1 and LOX in the first stage and LH2/LOX in the second stage which means far less LH2 than suggested but more RP1 and it should be noted that the economics given for the SD are a bit dicey as pointed out by NASA to TRW and Truax; To get to the given price point, ($600 to $59 per kg) you needed a pretty hefty flight rate of around 4 launches a month at least. Each delivering around 550 tonnes to orbit which then had to be 'serviced' by an on-orbit infrastructure capable of handling and processing 2,200 tonnes per month of payload. And you can't launch people on the Sea Dragon which was another thing NASA pointed out. Truax disliked and disparaged the NASA suggested guidelines that led to the "Excalibur" design concept, (most often calling it "Subcaliber") but in fact it was a more realistic payload capacity that MIGHT have been applicable to an expanded space program.
Sea Dragon and Laser Launch are in fact some pretty good examples of the two extremes of seeking economics by forgetting the reason(s) you're going into space to begin with. (And really a LOT of the proposed "mass" launch systems run into this issue) Sea Dragon had far to much payload for any near-term space program, even supporting Orion's. Similarly most laser launch systems put mass' of payload into orbit in "chunks" of a tonne at the most. (Usually less) Sure that translates out to a lot of "chunks" over a 24 hour period but those chunks are spread out all over the place and have to gathered and transported to where they actually need to go so a lot of each "chunk" ends up being supportive of the on-orbit infrastructure rather than actual payload. Most 'mass' launchers have this problem and only avoid this when they are massive enough to place significant payload into orbit in a single launch rather than over time. And of course to reach that point their upfront cost and resources required get very high, very fast.
So you end up looking at chemical reusable rockets which while having a lower economic case than say Sea Dragon, normally have a lower up-front cost than most mass-launcher systems and also have the advantage of putting you payload where you want it on every flight without resorting to large on-orbit infrastructure. And at some point, someone will point out that you can have the best of BOTH worlds by having a large chemically propelled reusable rocket with a large payload and you can even avoid the need for ANY on-orbit infrastructure! (Hello SLS!

) But keep in mind that flight-rate is a key metric, things are cheaper the more often they are used. Sea Dragon, Laser Launch, even Orion is going to end up being more effective the more often its used but more importantly you have to take everything into account and that includes propellant costs, refurbishment costs, and payload capacity per flight as well as over time.
There is in fact no 'golden bullet' single system that will open space to the everyone. Mostly because there is no single overall "plan" by anyone for manned space travel. It's always been a hodge-podge of concepts that gain and lose ground over time because unlike anywhere on Earth there's no real 'drive' to move people or civilization into space. And that right there is where any POD has to come from to build a timeline on. As long as mankind is just going to dabble in space exploration then there's no real need for the extensive space faring infrastructure and travel that actually being "space faring" requires.
Randy