Extreme speed is once again becoming a prized quality at the Pentagon after a two decade long hiatus following the retirement of the SR-71 Blackbird. Now Lockheed says it can build 3,800 MPH proof-of-concept jet in just a couple of years time, an aircraft that could lead to an fully operational “SR-72.” Amazing as that sounds, does the Air Force even need such an aircraft at all?

Lockheed says it sees these so-called hypersonic weapons, a term that refers to speeds above Mach 5, as a very lucrative business space to invest in when it comes to supplying the U.S. with future air combat capabilities. During Lockheed’s annual media day, the defense giant’s head honcho Marillyn Hewson said the following:


“Lockheed Martin has a legacy of making fast aircraft. We are now producing a controllable, low-drag, aerodynamic configuration capable of stable operations from takeoff to subsonic, transonic, supersonic and hypersonic, to Mach 6.”

This is a strong statement. She admits not only that the company is producing technologies such as thermal protection, avionics and aerodynamic shapes for a hypersonic aircraft, but seemingly also that they’re working on an actual aircraft design that would combine these technologies into a functioning hypersonic airplane.

A Very Fast Mountain To Climb

The big stumbling block for hypersonic flight is that it is very hard to optimize an aircraft to fly at such extremely high-speeds and be able to takeoff and land from conventional runways. Parasite-type configurations, where the hypersonic vehicle is lifted to altitude by a larger mothership and then launched on its mission, are one answer, but these concepts have big design limitations and they’re extremely complex and expensive.


Lockheed’s legendary Skunk Works stepped out a few years ago, seemingly out of nowhere, and showed off its SR-72 concept for a hypersonic plane that could theoretically operate from runways without the need of a launch aircraft or booster of any type.

It would achieve such a capability through a “combined cycle” engine concept. This engine system would presumably get around the traditional limitations of individual turbojets, ramjets and scramjets which can only really work over their own specific velocity ranges. Obviously, installing three types of engines in an aircraft that is supposed to be super high-performance is not an option.

Lockheed’s hybrid combined cycle propulsion concept aims at solving this issue by using a turbine engine at low-speeds and a scramjet at high-speeds, with both sharing a common inlet and nozzle design while keeping their airflow paths separated.

Lockheed now wants to test their combined cycle engine, and all the other crazy technologies they have developed to operate a real aircraft at sustained hypersonic speeds, in the form of a flying technology demonstrator. On that, Hewson said:

“Most importantly, we’re proving a hypersonic aircraft can be produced at an affordable price. We estimate it will cost less than $1 billion to develop, build and fly a demonstrator aircraft the size of an F-22.”

Lockheed thinks they can have this demonstrator flying by 2018, so we are not talking about a long-term development program here. In fact, the the stated timeline is so ambitious that it wouldn’t be surprising if the project was already underway in classified form.

Reconnaissance Has Changed

Even if Lockheed can build such an aircraft, does the Pentagon actually need such a weapon system? An SR-72-like aircraft would be unmanned and would have both a reconnaissance and rapid global strike role, but there are at least partial and possibly much cheaper alternatives to building a high-flying “silver-bullet” extreme performance jet.

The thing is, a super-high speed aircraft to replace the SR-71 has been sort of the aerospace-defense world’s white whale. Some very high-profile and respected journalists were seemingly obsessed with the potential existence of such a craft throughout the 1980s and 1990s, greatly enhancing the mythology of a possible “Aurora” spy jet.

It seems that so many have desperately wanted there to be a replacement for the SR-71 Blackbird, something even higher flying and faster than its predecessor, regardless of if there was ever even a real demand for one. In the end there has been no concrete evidence to support the existence of such a machine, and especially not a fleet of them in an operational form.

SR-71 Blackbird at sunset. Photo via Lockheed

There are plenty of good reasons that a Blackbird successor never happened. The fact that satellites could provide the SR-71's “moment in time” intelligence without risking human beings in the process was big factor. Air defenses have also come a long way as computer and sensor technology has advanced.

Yet maybe the biggest reason was that persistent, penetrating reconnaissance has been all the rage over the last few decades—not ultra-fast spy planes.

The SR-71 was limited to taking a snapshot in time, very similar to that of reconnaissance satellite. Its main advantage is that it could show up unannounced and be gone very quickly while satellites are much more predictable due to the confines of their orbits. Aided by stealth technology, slow but largely invisible to radar persistent reconnaissance aircraft could survey the enemy over long periods of time, without them ever knowing they were being watched. Even more important, they could do so deep in enemy airspace, not along their borders.

Think of it as the difference between taking a photo of an birthday party in a park from 200 feet away with a long camera lens, and shooting hours of video of that same event while mingling among the crowd. Obviously the latter tells a much more complete story of the party. The video camera also allows the shooter to record audio of the event. Similarly, with persistent reconnaissance capable of penetrating enemy airspace you can bank all types of radio emissions and even atmospheric samples over time.

If a picture is worth a thousand words, then a video is worth a million.

This reconnaissance revolution really began with Northrop’s Battlefield Surveillance Aircraft Experimental (BSAX), otherwise known as Tacit Blue. or more lovingly, the Whale. Its stealth design, hard to detect sensors, and data link technologies proved that a surveillance asset could survive and spy for long periods of time even while operating deep over enemy territory.

Eventually, this concept would evolve into the stunted RQ-3 Darkstar. Yet that program eventually would give birth to RQ-170 Sentinel. The RQ-170 has kept tabs on Iran’s nuclear program and helped hunt down Osama Bin Laden. It has also likely spied on other nuclear programs, such as North Korea’s, and friendlier ones too, such as Pakistan’s.

Although the bat-wing and stealthy RQ-170 looks cool, it is a downright humble machine compared to something like hypersonic spy plane. It is slow, small, doesn’t break altitude records and likely doesn’t even represent anything near the top end of American aerospace and weapons systems ingenuity. But it does what the Blackbird or its potential successor cannot, be the most obsessive of voyeurs, lurking and watching for hours on end in places it shouldn’t be.

The RQ-170 is just one program that has advanced the penetrating persistence reconnaissance concept, there are certainly others, and they are probably much more advanced than the RQ-170 ever will be.

The shadowy high-altitude, long-endurance penetrator dubbed by Aviation Week as the RQ-180, a Northrop product that has been all but admitted to existing by the USAF, likely takes the persistent penetrating surveillance aircraft concept to a much higher level, both figuratively and literally.

Sexy, But Not Necessary

With all this in mind, and considering the threats we have faced around the globe for the last 20 years, it is easy to see why a sexy hypersonic spy plane just isn’t a priority. Yet evolving enemy capabilities, shifting geopolitical realities, and the need to respond more rapidly to targets of opportunity and urgent surveillance needs are bringing very high-speed aerospace technology back into fashion.

Russia, China and the U.S. are working hard at developing hypersonic missile technology with the hopes that their blistering kinetic profiles can overwhelm potential enemy’s defenses and command and control chain. Yet hypersonic aircraft have been a more elusive prospect as the costs to develop such a large and complex vehicle are prohibitive, and the technology needed to make them a reality has been murky at best (until now, maybe.)

Can the increasingly cash-strapped Pentagon even afford one? Testing the technology in a demonstrator form for a billion bucks is one thing; the Pentagon blows money in far more egregious ways, and the science may be useful for other applications. But actually building a relevant-sized fleet of fully operation aircraft and putting them on quick reaction alert at a couple of bases is a whole other story.

So what do you get with an “SR-72?” You get something that can launch from California and be over North Korea in an hour and a half. A Mach 5-capable aircraft will take just two minutes to traverse the entire Korea Peninsula at the mid-point along the DMZ. Once there the jet can suck up image, radar and electronic intelligence for a moment before it is long gone.

If you stationed these aircraft at two bases, each halfway around the globe from the other, they could theoretically hit any target within just over an hour and a half after launch. This is an insanely impressive capability, but in order to do so you have to create a way to chuck a guided munition out of a an aircraft traveling at over mach five. Now you have a whole separate high-risk, high-cost munitions development program going on in parallel to developing the jet. Forget about slowing down to drop something—that defeats the whole purpose.

Then there is the survivability issue. Good luck making this thing low-observable, or to put it more simply, stealthy. The materials science and airframe shaping alone just to get to Mach 5 will be hard enough, and considering how much heat this aircraft will be propagating against a very cool and thin atmosphere, infrared detection will be a given.

So it has speed on its side, in a huge way. Yet with every measure there are countermeasures, and in an age where laser weapons are becoming a thing and missiles are capable of intercepting incoming nuclear warheads, betting so much on speed alone seems like a very risky proposition.

A Different Approach

The alternatives to such an aircraft really are plentiful. Arming submarines with hypersonic (or even high supersonic) capable land attack missiles would probably be far cheaper and more effective when it comes to satisfying the time-sensitive strike requirement. Said missiles could also be surface, land or air launched as well. By positioning these missiles near hotspots around the globe, they could be over a bad guy at least as fast, if not much faster than a super complex SR-72 and at a fraction of the cost.

A similar missile system could be built that lugs sensors instead of a warhead. After streaking over enemy territory it could data-link its information before self destructing. Smaller, much shorter ranged air-launched supersonic unmanned reconnaissance aircraft are also a more economic possibility.

When it comes to a time sensitive strike, you could also just use ballistic missiles. Of course, there is some controversy over possibly triggering World War III by mistake, but the fact is in a near-peer state conflict conventional ballistic missiles will be a heavily used weapon against the U.S. and its allies. Case in point: China is investing very heavily in this exact space.

Then there is the question of how many spy satellites could we put in orbit for the cost of a SR-72 program. Considering just the tech demonstrator will cost a billion bucks (and that is in “Lockheed dollars!”), a small fleet of full-up operational hypersonic vehicles will likely run into the tens of billions. That means we could buy dozens of new spy satellites for the cost of an SR-72 program.

Finally, there is the question of having to fill every potential need with a 100 percent solution. Couldn’t we just forward-deploy stealthy subsonic drones to areas where intelligence gathering may be urgent, and launch them when needed or even keep a couple always in the sky for re-tasking?

Sure, they may not get there as quickly, but you can buy hundreds of drones for the cost of SR-72 program.

In the end, the SR-72 idea is very exciting and very cool. Lockheed knows how to pull at any tech or aviation buff’s heartstrings with killer renderings of the jet and promises of obscene speed.

But just because we can do something does not mean we should do something, and sadly, a new Mach 6-capable bomb-chucking unmanned spy plane fits into that category.