Aircraft fly by means of two forces: motive (propelling) force and lift. For example rockets fly due to motive force generated by their chemical engine while kites fly due to lift. Lift is a force perpendicular to direction of movement in the medium, and unrelated to the propelling force which is parallel to the direction of movement. As long as the fluid (e.g. air) moves around the airfoil it will spontaneously generate lift due to pressure differential. This is why a stationary aircraft will fly if sufficient volume of air around it moves - it floats on thicker air beneath it and rises into the thinner air above it.
However wings do not generate lift equally in all directions - the dimension perpendicular to both direction of movement and lift is most important. This is why dragonflies have very long thin wings, as do all gliders. In variable geometry systems wings extended maximise lift at lower speeds and folded wings minimise drag at higher speeds. Greater lift helps during take-off and landing when speed is necessarily low. It also improves lift when carrying heavy payload.
Extended wings also help when flying at very low altitude, as air has greater density there and flying at low altitudes is more dangerous at higher speeds.
Bombers like B-1, Tu-22M and Tu-160 have variable wing geometry because they are supersonic and drag becomes primary concern at supersonic speeds which are sufficient to impart motive force on the plane even with reduced lift.
They are supersonic because their primary tactic includes penetration of enemy airspace at low altitudes (below radar horizon), releasing munitions at target and then escaping at supersonic speeds.
B-1 has variable geometry because it was desiged in early 1970s when most of its intended targets were stationary (including SAM sistes which were targeted by AGM-69 SRAM) and enemy interceptors were less capable (MiG-25 with R-40 etc). B-2 was designed for a different threat matrix - with Soviet mobile ICBM launchers as targets and MiG-31 with R-33 as primary interceptor. Therefore B-2 couldn't rely on either speed or pre-determined target location. This is why it chose the most stealthy shape which is the flying wing.
These studies never approach alternative designs with an equal interest. These serve to illustrate the original point to people who lack the knowledge i.e. congressional staff and representatives.
There would never be a design other than a flying wing for a strategic bomber because all those calculations have already been done in the past, but any new person on the Capitol Hill, or an old one who got a donation from a competing interest, can begin to question the validity of design. Decisions about funding are entirely political, they are pre-determined according to funding interests and need to only be plausibly deflected in the public view. So showign that you've done the exercise and came to decisive conclusions - as well as being able to present that conclusion to the general public - is crucial.
As for design objectives - it's simple:
Bombers do not approach the target at supersonic speeds because it's too costly in terms of fuel, prevents use of very low altitudes and increases the signature. Supersonic speeds are only viable for departure but then the bomber's position is known and interceptors and long-range missiles will have greater speeds than those achievable by bombers. The Valkyrie proved already in the 1960s than 2-3Ma isn't viable for a strategic bomber.
The confusion about what the optimal design can come also from interaction with Russian propaganda. Russians make a big show of what they have which very often leads to absurd situations where an obsolete airframe design like that of Tu-160s is touted as equivalent to B-2/B-21. They claim that PAK-DA will be equivalent (or better) than B-21 but they have nothing to show for in the program apart from artists impressions. And so the nonsense rolls on repeated by "experts" online.
There is no debate on the optimal shape of a strategic (i.e. long range/long duration) bomber and if H-20 turns out to have airframe deviating significantly from flying wing it will be my biggest surprise wit PLA to date.
The "pop-up" threat with regards to bombers is nonsense. Bombers once deployed are entirely on the mercy of the environment. The enemy has all the advantages - speed, altitude and numbers - which is why a good mission plan and surprise are necessary.
I recommend looking up my Desert Storm thread for comments on the difference in how the use of F-117A was portrayed in the media and how it was done in reality by USAF. This is the quintessential "you don't know jack about war" case study:
Desert Storm - overview, data & statistics
The following is a collection of maps, tables and quotations from publicly available sources with heavy emphasis on Government Accountability Office's report "Operation Desert Storm - Evaluation of the Air Campaign". I divided the whole set into five posts: air superiority over Iraq -...
www.sinodefenceforum.com
The same applies to bombers - you know the media's side of the story which means you don't know jack.
The bomb bay is at the bottom of the aircraft. The only sensors that will see it are ground radars within range and that range is not as large as commonly thought. Terrain, horizon, power reduction over range - all play into the probability of detection. And bombers today won't be flying over the target but releasing stand-off munitions 100km from the target at minimum. The shoot-down of F-117 in Serbia was an accident no matter how hard Serbs and Russians want to convince you otherwise. And in general GBAD shooting down targets at range is a much harder problem than it is commonly thought - as made evident by the numerous friendly fire incidents during the Russian invasion of Ukraine.
And that's besides the question of new generation of bombers being so much more than just bombers.
No it's not. Take your fanboy fantasies somewhere else. Preferably to a library where you will learn what actually broke the Spanish and Dutch empires (hint: it wasn't the destruction of their navies).
