When I was developing the M-II, I came across
this quote by Elon Musk:
I wanted it to look like the H-IIA so much, that I decided to go with the LOX/Kerosene 1st stage (to differentiate it from the H-IIA) + LOX/LH2 2nd stage + monolithic solid boosters (My justification was to have commonality with Negi-5, which is based on M-V/Epsilon) in spite of this. And because I had sufficiently sized solid boosters, horizontal rocket integration wasn't an option.
"A second, solid fueled system added to an existing liquid fueled system also adds an additional level of complexity, which also adds to costs."
"Rockets assembled and integrated horizontally, not vertically, which Space-X considers less expensive and less hazardous."
Should the M-II receive a major overhaul/retcon?
Don’t change the M-II. I like it the way it is
Ignore that statement. Being serious now.
Any response I give ultimately depends on what you mean by “major overhaul/retcon”.
Yes, if the M-II is getting an evolution path (like the
H-II to the
H-IIA and
H-IIB), then I see no problem with it, since NASDA/JAXA did the same thing and HASDA could also do it (M-IIA, anyone?).
No, if the actual M-II will be changed. Several reasons for this:
1) Might result in modified addons, etc. This is a foolish stupid reason, so feel free to ignore/facepalm.
2) Different configurations, different results, different problems.
RP-1/LOX 1st stage, LH2/LOX 2nd stage, and RP-1/LOX (Ariane 4-style) strap-ons: Maybe the best "new" configuration to go with. Might require a change in infrastructure.
RP-1/LOX 1st stage, RP-1/LOX 2nd stage, and solid fueled strap-ons: Upper stage no longer high-energy, so will not carry same payload into orbit. Decreased payload mass may not be worth the lower launcher causes. Better to ditch the solid fuel strap-ons.
LH2/LOX 1st stage, LH2/LOX 2nd stage, and solid fueled strap-ons: Nothing wrong with this, since JAXA has one called the H-IIA/H-IIB. Might eliminate the M-II Heavy, since LH2 isn’t that good at ground level and you would need another form of thrust augmentation.
Another reason you shouldn’t go with
2) is because it eliminates the only thing that makes the M-II different from the H-II (RP-1 first stage), and thus, the only reason it could/would exist. For the same reason, I would never contemplate making the Hermes use LH2/LOX for the CCS
EVEN if it does fall short of expectations, since if I did that, it just be a smaller SLS and there be no point at having it (the M-II, I think is
slightly smaller than a H-II, too). I think it has to do really with whether or not you want to make a LV you designed yourself a virtual copy of another real-life LV, etc.
Lastly, JAXA seems to be content with the H-II even though it is a three-part rocket system. Maybe HASDA should/could too.
If your problem also includes horizontal vs. vertical integration, I would go with horizontal integration, since a few rockets still do it (Delta IV, Falcon 9, Antares) and it seems easier and more efficient to do.
