Such limited manoeuvring also requires planning and 90 minutes between passes. Lots of opportunity for bad guys to push their missile back into a hangar.
An atmospheric aircraft can follow an arbitrary course to take in as many targets as required, can be rerouted on a moment's notice and can approach from unexpected vectors to catch the target out in the open.
The high altitude spy planes (U2, SR-71) were mostly to prevent being shot down; surviving to return the film to base.
Drones don't need to bring film back, and it's not such a big deal if a few of them are lost.
Though I suppose that you could try to make your drones so cheap and in such volume that shooting them down becomes logistically and economically infeasible, but that's another strategy entirely.
The whole idea of the SR-71 was that it went so fast that SAMs could just barely not catch up to it before they ran out of fuel. Any other plane couldn't outrun them, but the Blackbird? Well, Mach 3.4 will give you some breathing room.
I imagine thought a little snake left/right might compromise getting the images that was the point of the mission.
Missiles and radar tend to operate in a "bubble". Even with the Russian S200 system at 190 miles range, the time you spend in that "bubble" when you're at 70k ft is not often long enough to do anything. That also assumes the aircraft directly overflies the battery. You can play games like pointing the camera sideways and observing from an angle if you know there are going to be angry people with guns nearby.
- There is no real need for SR-72 to be manned on all flights;
- Hypersonic plane would be very good for small (2m wingspan) drone delivery behind the enemy lines fast (in half an hour). This was already a concept with M-21/D-21, but now the drone part can be much smaller and one plane could carry more than 4 of those.
Satellites are quite limited when you need to make fast decisions. Hypersonic plane will move about 7 times slower than an optical recce satellite, yet it can maneuver very fast if you need to relocate the imaging area and can get at least 10 times closer to the target. Instruments can be selected/improved even after the first flight of the plane -- not true for the satellites.
The "Misty" satellites came up on HN last week related to the SpaceX launch and failure.
https://en.m.wikipedia.org/wiki/Misty_(satellite)
http://www.armaghplanet.com/blog/the-real-mystery-satellites...
"A week after launch, reports were released from the Soviets that six bits of debris had been detected suggesting an explosion had occurred. The Pentagon announced that any debris would decay after six weeks. The amateur astronomers and observers that were tracking this object only catalogued five out of the six pieces. Six months later an unidentified satellite was discovered in orbit on a similar trajectory to that of the classified payload was released, leading the satellite spotters to suspect it was the missing piece, nick-named Misty. However a couple of noticeable manoeuvres later, Misty disappeared again. Perhaps the ‘explosion’ was a decoy to put Misty into place unbeknownst to the Russians."
Here's a diagram of their style orbit: https://www.planet.com/docs/spec-sheets/spacecraft-ops/monit...
2. The Space Shuttle suffered from many costly design compromises due to its excessively large hangar bay.
Given #1 and #2, there are four likely kinds of classified missions that the Space Shuttle undertook.
1. Stealing Russian military satellites.
2. Returning American military satellites to Earth.
3. Launching American military satellites into unpredictable orbits.
4. Refueling American military satellites, which allowed them to change to a new, unpredictable orbit.
It's entirely possible that the Space Shuttle only engaged in some of these tasks... But it's difficult to conclude that given the very odd design of the space shuttle, and the very lengthy missions that it undertook, that no satellite servicing/orbital shenanigans took place.
Yes, satellites can change orbits using on-board fuel reserves, but due to the tyranny of the rocket equation, those reserves are limited - and are unlikely to allow a very large inclination change (Inclination changes are incredibly fuel-expensive.)
Likewise there is no such thing as an unpredictable orbit. Orbits are predictable, by definition. Any country with a good set of radars, telescopes, and IR sensors can find the exact orbit of every single satellite.
The Space Shuttle was certainly used for launching American military satellites into regular predictable orbits. They might have done a refueling mission at some point as a proof-of-concept but even that seems unlikely considering that it's always cheaper to just build and launch a new satellite.
If SpaceX succeeds at lowering launch costs then it would be easier to launch many small and disposable spy satellites than ever to bother refueling one.
Nonetheless, the point is that satellites are limited as to opportunities due to limited availability and limited time windows. This does argue that there ought to be a role for an SR-71. I'm not sure there's much of a role for an SR-72, but certainly for the SR-71 there ought to be.
Judging by the publicly-released payload specs for the DoD-operated Boeing X-37 spaceplane, it should be able to deliver about 2000+ L of hydrazine, compressed Xenon, or other suitable fuel in a single launch.
Edit: It looks like DARPA has been experimenting with "space gas station" experiments since at least 2007.
https://www.space.com/3644-prototype-satellites-demonstrate-...
A LOT of fuel. So much so that even if lifetime wasn't an issue, it makes more sense to launch additional satellites in the proper inclination, rather than moving one.
I know that, in one instance, a company wanted to use the moon's gravity to change a satellite's inclination, as it was cheaper to all the way to the moon and back (and then circularize again). That maneuver seems to be patented, though.
http://www.popularmechanics.com/military/aviation/news/a2602...
When you control the sky’s you don’t need to fly at 6000 mph.
We have bases in Pakistan and Afghanistan, for example.
Which mission profiles are you describing that are actually needed to fly at hypersonic speed? A lot of these countries are quite small for that speed. A 100 miles a minute.
Mission profiles better suited to a plane than a satellite: anything that requires loitering, returning to a target, anything that requires a curved path that a satellite cannot fly or anything that requires close up - optics on satellites are good, but fundamental physics limits the achievable resolution. Hypersonic speed might not be required to fulfill the actual mission, but it allows shorter response times on all spots. It also would allow evading most intercept attempts.
So, technically and at least according to ICAO, these birds flew/fly above a nation's sovereign airspace. That doesn't stop a nation-state from attempting to down one of these birds, of course.
I think the general rule is that sovereign airspace covers air-breathing planes but not spacecraft. From your link:
> There is no international agreement on the vertical extent of sovereign airspace, with suggestions ranging from about 30 km (19 mi)—the extent of the highest aircraft and balloons—to about 160 km (99 mi)—the lowest extent of short-term stable orbits. The Fédération Aéronautique Internationale has established the Kármán line—at an altitude of 100 km (62 mi)—as the boundary between the Earth's atmosphere and outer space, while the United States considers anyone who has flown above 80 kilometres (50 mi) to be an astronaut.
stealthy or speedy aircraft could work over more hostile places and add to the satellite capabilities. Maybe there are things you can sense from 10 miles up that you can't at 100mi. And maybe there's some brand new gear that you don't have in space yet. And maybe you want to time your picture with some unpredictable events on short notice. there are a ton of reasons to have this variety of capabilities.
I could see utility in being able to rapidly deploy a team of special ops, or specialized unanticipated equipment, to a faraway location. That it can do things a missile can without being a missile is also useful. (Suppose you need a bunch of drones over a random location. You could launch a missile and risk (a) breaking your birds in launch and (b) someone thinking you're flying nukes. Or, you could use this plane.)
This won't be landing on any improvised airstrips, and a hypersonic configuration won't be able to go slow enough to drop paratroopers.
The more interesting impact would be on the design of the plane doing the drop. While I think you could keep the paratroopers alive, I'm skeptical there's any way you can go that fast and drop a large container. I would expect the process to destroy the plane by making it too unstable.
The Osprey is probably the fastest troop carrier, so you would need to identify some use cases it can’t do then figure out if the cost is worth it. Traditionally SF get there by jumping in and then hiking cross-country, is there a use case for getting them on the ground in a couple of hours?
Galus, what do you base your claim on that a hypersonic config can't go "slow enough"?
2. Higher resolution imaging could still be quite useful. For example, if we could possibly find all of the Chinese DF-21B anti-ship ballistic missile launchers, this erodes the deterrent effect of that weapon, which then increases the value of the US aircraft carrier groups.
Missiles are generally powered by rocket motors - they don't need air intake.
Missiles are also generally one-time-use - you send it somewhere and don't expect to reuse it (also it usually explodes)
I suppose it might be possible to increase payload per fuel efficiency, but the only reason the military would probably care about that is cost, and the rocket engineering is already paid for and proven.
It’s also not entirely true, tomahawk cruise missiles for example use turbofan engines with a solid state booster.
https://en.wikipedia.org/wiki/AGM-86_ALCM - "All variants of the AGM-86 missile are powered by a Williams F107 turbofan jet engine"
https://en.wikipedia.org/wiki/Tomahawk_(missile) - "After achieving flight, the missile's wings are unfolded for lift, the airscoop is exposed and the turbofan engine is employed for cruise flight."
https://en.wikipedia.org/wiki/Harpoon_(missile) - "Power plant: Teledyne CAE J402 turbojet, 660 lb (300 kg)-force (2.9 kN) thrust, and a solid-propellant booster for surface and submarine launches"
https://en.wikipedia.org/wiki/Kh-55 - "It is powered by a single 400 kgf Ukrainian-made, Motor Sich JSC R95-300 turbofan engine, with pop-out wings for cruising efficiency."
The hypersonic missiles use a rocket to get up to speed, like:
https://en.wikipedia.org/wiki/Zircon_(missile) - "A booster stage with solid-fuel engines accelerates it to supersonic speeds, after which a scramjet motor in the second stage accelerates it to hypersonic speeds."