All transport category aircraft run their takeoff data based on the loss of an engine at the worst moment. Any current 2-engine product has the required performance for an equivalent weight. (Remember, stopping is a critical element of this, an area where the current -135 doesn’t do really well, especially due to the high runway speeds required because of it’s 1950’s wing design) If 2-engine airframes of an equivalent weight class really suffered from a performp;ance issue, you’d see a lot more 4-engine airplanes rolling off of the line today. Performance is important to the airlines too…
The 767-200ER has an empty weight about 40,000 lbs more than a -135 and a max takeoff weight about 60,000 lbs more than a -135. Wingspan and length are about 25' more than a -135. So, while it is slightly larger, it is in the same class and would be a good replacement, even though it is based on a 1983 design.
The 777 is 70’ longer than the -135 in length and wingspan, and that will impact the number of suitable airfields you can use, ramps, etc. As much as I like the 777, it really isn’t the right plane to replace the -135. It’s bigger than a KC-10. You’d have to buy a lot fewer of them, have fewer booms in the air and would be airfield limited.
-135 Carbon airframe derivative is a nice idea, but the 1950s design is WAY out of date. (Better wings, environmental, flight controls, etc. etc.) We need tankers now, not after another 10 years of R&D, design and tooling up a whole new assembly line. Buying a current product is the answer.
50K is an arbitrary number for the 737, I have no idea whether it is accurate or not for a 737-type, but it seems about right. TankerDriver, your large offload experience may not be indicative of the overall requirement. (maybe it is though, I honestly don’t know…) I remember taking off with large fuel loads and offloading it all, but I also remember taking off with 160K+, offloading well less than 40K and having to dump fuel in order to land the jet in time and turn it to the next mission. How many pounds of gas were dumped the first night of DESERT STORM? Maybe we are smarter now and plan better but maybe there is a niche for a number of smaller tankers that can cycle more groups of fighters at once. Maybe the niche capability is not worth it when compared to the economy of scale of buying more of a single type of airframe. (i.e. the Southwest airlines model) I don’t know, but it probably is worth looking at.