High atmosphere combat - designing the optimal bomber

Question

I've done a bit of research about high atmosphere bombers, but none of my searches really address my issue.

What features would allow a combat bomber craft to excel at high atmosphere (thermosphere-stratosphere) work?

This craft should be able to withstand the dangers of space for 20 minutes. However, it does not need to function while in space.

the payload capacity should be around 30,000 pounds.

Answers about space-to-air deployed craft and ground-to-air craft are acceptable.

edit: I've received multiple comments about how unnecessary bombers are.

in my setting, bombers are required because standard high velocity bombardment techniques don't work against urban planets with shield generators (it would take tens of warships weeks) . bombers can get through because they can slow significantly to get through the shield before dropping their payload.

therefore bombers are standard procedure because of cost efficiency per warhead.

Answer 1

You don't need a bomber, you need a parasite aircraft carrier

bombers are required because standard high velocity bombardment techniques don't work against urban planets with shield generators (it would take tens of warships weeks) . bombers can get through because they can slow significantly to get through the shield before dropping their payload.

This clarification gives us a good framework for what these bombers need to be able to do: launch from a trans-planetary spaceship, decelerate from orbital speeds, drop their payload, and (optionally) pull out. During the slowing-down process they are presumably sitting ducks for enemy craft, which are not constrained by having to brake and want to blast those bombers with air-to-air missiles.

I say optionally because you run into the delta-v problem. And even with a super duper futuristic setting, no military is going to pour resources into something when it doesn't need to.

Slowing down takes fuel

XKCD illustrates the problem with re-entry: being in space isn't an issue of being high but of going fast. Things in orbit stay in orbit because they are moving so quickly that by the time they fall to Earth, they have already missed it.

Your bombers are going to need to decelerate (which takes energy), then pass the shield, fire their onboard missiles, and then begin the ascent. This takes twice as much energy as just slowing down, firing, and then letting the craft explode. And the tyranny of the rocket equation means that you also need fuel to carry the fuel. You save 90% of the weight by cutting out the recovery portion (the cost with a futuristic power plant will be less, but never zero).

What you have is a MIRV that uses its primary engine to slow down rather than speed up.

Bombers don't do "combat" without escorts

We have a new participant in this equation - the mothership - that makes this whole thing work. Since the "bomber" will be disposable you want it stripped down as much as possible. We can use the grisly Ohka as an example: lacking everything a plane would need except for wings and an engine. It has little fuel because its parent plane - the G4M would get it most of the way there.

So the doctrine for your bomber would look something like this: a mothership would either first enter orbit and then launch parasite carriers, or launch from concealment and have the carriers approach the planet by themselves. If it is the latter, the carriers carry fighters among their parasite craft.

The carriers then release their "bombers" which begin the deceleration process. The slower they get the easier it will be for them to get shot down by enemy space-based missile platforms. The carrier (which is going fast) has now overshot the zone of engagement, so it will be the job of those escort fighters to slow down somewhat alongside the "bomber" and provide screening fire against enemy missiles. Worst comes to worst, the fighters can act as decoys for the missiles, allowing the bomber to make it through the shield. As soon as that happens, there's no more "combat" - the "bomber" shoots its guided missiles and its job is done.

On its next orbital pass, the carrier can pick up the surviving fighters without significantly decelerating if it has some sort of tractor beam, and book it back to the mothership. If the mothership launched from orbit, then the carrier and the fighters can both return under their own power, or get pulled up from a lower orbit by a similar tractor beam.

Answer 2

Speed, detection, rockets

We have all seen Tom Cruise redlining his fighter, the metal under tension, going straight into the danger zone. Both Top Gun and Top Gun: Maverick return us to the romanticism of the dogfight, where close quarters combat between fighters takes the uttermost skill and any mistake, or simply just 99% means death.

And it is completely fiction. In the second one they remedied this problem in part by focusing on flying a certain path. You might have heard that the new JSF plane is dog shit in dog fights compared to previous generation Russian and Chinese planes. This is absolutely true. The reason? If your plane needs to dog fight, something has already gone horribly wrong.

Against what games and other media tell you, much of military technology is about making it as easy as possible to kill, regardless of skill. That makes even your substandard grunt able to use a shoulder fired rocket launcher to blow up tanks. With modern planes this is no different. The idea is that the enemy is detected even over the horizon, far beyond what you can see. The plane is purely used as a flying missile launcher, able to quickly reposition if needed. In an ideal scenario they fly out, fire x missiles, get x kills, and they return to base while never having seen more than a few angry dots on a radar. Dog fights should not occur.

SR71

To get a more accurate picture, let us look at the fastest (confirmed) plane in existence. The SR71 Blackbird. It is only exceeded by the X15 and ither X variant prototypes. The SR71 used a few things to its advantage. It had one of the first forms of stealth. It flew so high it was inconceivable for those times that anything did fly there. If it would be detected, there was practically nothing that could reach that high, let alone catch up with the blistering speed.

As the plane is already a pressurised tube to protect the people inside, it shouldn't have too much alterations to fly towards space. However we can look at the X15 for further information. This wasn’t necessarily a practical plane, as it used rockets for it's short flight and most X variant planes needed to be launched from another airplane. This plane could reach the edge of space. Though I can't find much about the materials used, it likely is using much of the same materials as the SR71. You can incorporate designs of both for a plane that can cuise higher, possibly using rockets for periods of flying roughly 80+ km and higher.

And do we need to think of more? These seem to be an all round description of what you need. A modern version of the SR71 blackbird.

For detection you can have specialised planes that do only that, and might not fly high and fast. Alternatively you put a lot of detection technology in your new plane do it mostly for itself. In addition, it'll be embedded in a world wide communication system, so the planes can communicate any position and target as quick as possible to each other and command.

Be a new type of fast and stealth. Technology like ramjets, envelope marerial and aerodynamics have gine leaps and bounds, squeezing ever more performance for speed and stealth.

Have a few special ways to have any payload inside the plane, and a special way to launch them so the plane doesn't tear itself apart when something opens on the plane. My amateur bet would be to simply open a tiny door in the back of the plane, throw out the rocket and activate the rocket a bit later. Experts probably have better solutions to deploy payloads at those speeds, which is a hazard all by itself.

There you have the new fighter. It can detect enemies and communicate it to another plane if they already overshot it. They are so fast practically nothing can take them down. They fly so high they can go into space temporarily, until the lack of atmosphere pulls them back. They are stealth to make detection as difficult as possible. They are basically gone from enemy airspace before they know it, only seeing some ordinance hit home out of nowhere.

Answer 3

This started as a comment, but kinda grew

What do you mean by 'Combat'? Your question is talking about Bombers and Interceptors - in which case the answer is simple - something like the Mig-25 Foxbat or English Electric Lightning II - Basically a really really big engine and absurd thrust-weight so that the Interceptor can put the burners on, go vertical and intercept the Bombers as quickly as possible - most likely following a parabolic ballistic trajectory (like the Mig-25 did for it's 'Space Flights').

As it stands - the Mig-25 is pretty much everything you want - just needs to be paired with a decent missile system (AKA - Not Russian...).

But my Gut feeling tells me you want something more than just a Ballistic trajectory and glorified missile deliver system - something tells me you want a bit of Dog-fighting capability in the upper atmosphere.

So The first part of Aircraft design is very much as above - Really powerful engines - as much Engine as you can fit in the airframe.

Now - surviving the extremes of 'space' - this is not really the issue you think it is - The airframe is already a pressurized vessel and sealed, they are capable of withstanding the coldness of the upper-atmosphere, which is curiously similar to the coldness of space.

The only thing you will need is a means to accelerate and move when the air-breathing engine cuts out. Easiest option would be something that mimics the Pegasus Engine with the bleed-air system that directs air jets to the wings, tail and nose of the aircraft - the only difference would be that this would need to be powered by a Rocket of some description or it could be powered by a tank of compressed air stored up from when the Engine is operating in the Atmosphere.

This adds some complexity to the design - either we need to add weight, bad or we need two engines Weight and bad - which kinda makes me think that if you want a dedicated space interceptor, you would just have a rocket engine full-stop - similar to the Me 163 Komet - (except without all the nasty T-Stoff chemicals melting pilots alive).

If you have questions - feel free to clarify.

Answer 4

That's awfully high up. I can think of a couple viable things that you would actually be doing up there for good tactically-backed reasons:

1. Dropping bombs intended to reach the ground at very high speed, either to use the kinetic energy as a weapon itself or to avoid getting shot down;

2. Deploying anti-satellite weapons from a spot closer to orbit, so that accuracy is improved; or

3. Otherwise reinforcing stuff in orbit.

In all cases, the most important thing is going to be maintaining stability. Super high up in the atmosphere, the problem that aircraft like yours will face is that there is not much air for the craft. Wings become less and less valuable and produce less and less lift, so alternative modes of stability will be needed, like reaction wheels or even anaerobic booster rockets. Additionally, life support will be increasingly difficult, and you will need to make this aircraft more like a spacecraft in terms of redundant systems. If you want to keep the occupants alive.

... actually, why do you need occupants? Make this a dronecraft. This fixes a lot of things: no super-heavy radiation shielding, no pressurization, no oxygen recycling, none of that pesky stuff that spacecraft need to survive, but you can still have all the command-and-control and you can still deploy whatever you need to deploy that high up in the atmosphere.

So, I guess, the most important thing for your aircraft is for it to be a drone.

Note that returning might be an issue. It will take a lot of $\mathrm{d}v$ to get all the way up there, and if you're going for maximum-maneuverability maximum-size-bomb bays, you might not have enough fuel to safely decelerate back into the atmosphere. Of course, you shouldn't care if a drone gets burned up vs. a human, so...

Answer 5

I’m going to ignore what happens to the pilot. The guy volunteered to become the soup kitchen, as far as me is concerned.

You want speed and manoeuvrability. Regarding the source of speed, there is nothing like a ramjet. A radioactive ramjet is Project Pluto.

You want to have an aerodynamic shape for flying fast. And if you go fast and turn fast, you destroy yourself. So no fast direction changes, unless you have the built-in ability to break fast to speeds where you can change direction.

For that you need a drag parachute. Which is limited. Unless... you have a system of "parachutes" capable to deploy out of your hull, applying drag while gliding back on your hull and folding up. In the ideal version, I imagine would look like carbon fiber hair, you can put into the air on demand and fold back up into a smooth air-flowing surface once the breaking is completed.

Then it’s going back up to speed to escape projectiles and weapons. This whole thing is about the fighter, after it has been discovered and engaged. Everything before is covered by Perun in The race for 6th generation fighters - drones, lasers & future air dominance.

Finally, the optimal bomber is build from bombs. As in the structure itself, it is made of mostly bombs, glued together by a dissolvable substructure. All that returns is not the bomber; what returns is the engine and the pilot cabin. The rest is payload, wings glued together from a ton of bombs, flocking away at the target. What returns, looks like a cockpit on top of an engine.

Answer 6

The Thermosphere is for satellites and the Stratosphere is for airplanes.

At your aircraft's maximum cruising altitude, the air becomes so thin that you can not rely on lift to keep you in the air. You will need to approach orbital speeds in order to maintain altitude meaning that your bomber needs to be to get up to VERY high speeds. In contrast, if you are flying in the Stratosphere, air pressure is too great to maintain orbital speeds because the air resistance would burn you up. So your aircraft needs to take both environments into consideration.

What you are suggesting needs to be some sort of spaceplane that takes off into an orbital pattern, deploys its payload, and then returns to Earth like a glider. The Space Shuttle was the first such vehicle, but it was way bigger than most modern bombers and at 1.5 billion dollars per launch, not really a sustainable military platform. What you will want is probably something more in the weight class of a fighter-bomber (about 5-10) times smaller than a space shuttle, but otherwise capable of the same sort of operations.

You will also need to make your price per kg to launch much lower. Luckly, there has been a lot of research into making space planes more affordable than the space shuttle with the most successful being the X-37 program that can launch the approximately fighter sized space plane into orbit using a falcon 9 rocket, at which point it can act as an orbital weapons platform for hundreds of days before having to return to Earth. At a total launch cost of just 62 million dollars, and enough bay capacity to carry several tons of bombs, the X-37 could very quickly evolve into the exact sort of weapon system you are asking about.

While this is still a very hefty price for weapon deployment, it does come with the advantage of being able to fly over the missile defense systems found near the conflict areas and attack sensitive targets deep inside enemy territory where they probably did not think they would need a strong missile defense grid. Even if the cost per bombing is 10x as expensive as alternative means, this could force a hostile nation to spread thier air defenses thin trying to guard a lot more potential targets. The strategic value of thinning of enemy air defenses alone could make the orbital bomber worth its cost. More so if those back line targets include things like aerospace factories, microchip fabs, and other such target that could individually hobble a nation's war effort.

What would set an orbital bomber apart from a more barebones missile satellite is that the bomber could have more defensive capabilities like decoys, active-defenses, ECMs, and more expensive targeting, detection, and evasion systems which might be prohibitively expensive for a single use ballistic missile. All the advanced technology that goes into modern fighters can cost hundreds of millions of dollars which is why we still often prefer to use bombers instead of disposable cruise missiles ladened down with all the same features.

Since it can orbit for so long, the idea would be to put it in the sky before you have a target, and then adjust its orbit once you know what you are looking to attack. And once the bombs are spent, you deorbit it and land it just like a normal aircraft so that all of its expensive electronics and defense systems can be recycled for future missions.

Answer 7

The Thermosphere is already pretty much in space. At that altitude, the atmosphere is so thin that trying to use it for lift just isn't happening. 0.001 kPA of pressure is basically non-existent. That means that this is really a spacecraft you're building for that altitude. Since you said high-altitude bomber, I'll assume you mean more in the low to mid-stratosphere. This is a bit more manageable, although the pressure is only 20% of the level. At that altitude, you can either make a massive wing or go really fast. Since this is a bomber, speed is probably a priority. It should prioritize going at near hypersonic speeds, probably using a ramjet. The faster you go, the more lift is generated, and as a plus you also are harder to shoot down.

Other than that, is should also be fully enclosed with its own life support system capable of operating for extended periods, as the stratosphere is enough to warrant that. Radiation shielding as well. Really, it should also be built a lot like a spacecraft except with wings to fly instead of orbiting, much like high-altitude bombers of our own world, which used a lot of spacecraft technologies. As a bonus, that also means most of the work is done to survive in space, and it isn't too much of a stretch to make it capable of that as well.

TL;DR The thermosphere requires a spacecraft, but the mid-stratosphere is more doable. Prioritize going as fast as possible to generate more lift, which as a bonus makes it hard to shoot down.

Answer 8

Building on the excellent answer by SPavel.

Reverse Skyhooks

SPvael's answer suggests that the bomber should work like a rocket in reverse, by using a huge burn of fuel to slow down from orbital speeds, then it is slow enough to pass the planets defence shield and drop its bombs.

I think bombers based on a skyhook (https://en.wikipedia.org/wiki/Skyhook_(structure)), but working backwards would be potentially a lot more efficient, and also more exotic. The "bomber" consists of a "bomb bay" and a "counterweight" connected by a very long, very strong, cable.

A diagram of the idea:

The bomber is set into a very fast rotation, so that the bomb bay and the counterweight are swinging quickly around the bomber's centre of mass: like a giant propeller. Now, the bomb bay comes swinging on down towards the planet. Its in orbit, which adds a lot of velocity, but its spinning fast, and you have set it spinning so that these two velocities cancel out. Its like how even in a car going at 100mph the instantaneous velocity of the bottom of the cars wheel is zero, (assuming no sliding). You don't go for exact cancelation, only enough so that your bomb bay slows down enough to pass the shields. It drops its bombs, then shortly after gets swung back out to safety by its rotational motion.

Answer 9

You have three main features needed.

1. Be difficult to detect. If you're carrying a payload, you're automatically less manoeuvrable than anything which might intercept you.

2. Carry enough bombs/missiles that some of them will get through. Israel's Iron Dome works great against small numbers of incoming missiles at a time. Throw a thousand at it simultaneously, and over 90% will be hitting targets.

3. Don't care about it coming back. As soon as the bombs start falling, the interceptors know where you are. Maybe that payload gets through - but there won't be a second delivery from that plane or that crew. You're going to run out of aircraft and crew very quickly.

The only bomber that meets these criteria is ballistic missile a with MIRV warheads. Everything else is worse, which is why strategic bombers became a thing of the past in the 1960s and simply aren't coming back ever.

Answer 10

I know you mention that your world has some sort of shield tech that only allows slower moving objects to get through hence the need for slow moving bombers vs just projectiles.

Bombers are slow, if your tech is advanced enough that you can build shields that large then you can probably shoot down a couple of slow moving planes.

Another issue is getting an entire bomber into space is going to require an obscenely large rocket. I guess the space shuttle could do it but it isn't exactly a bomber.

What could work is a glider, just get a big plane and stick gliders under each wing with multi-megaton warheads in each one.

Release them high in the atmosphere and let them slowly glide through the shield from a nice safe distance. As soon as they get through the shield, light the rockets and watch them smash into its intended target at hypersonic speeds.

If you wanted to be super sneaky, put each glider on an ICBM and release the glider at a shallow angle somewhere in the stratosphere. As the glider is reentering, fire off smaller rockets facing forward along with multiple airbrakes to slow the glider to a reasonable speed.