In 2006, a team from Boeing proposed an incredible new use for America’s legendary F-15 Eagle that called for mounting a 45-foot rocket to its back. This rocket-carrying fighter would be given the seemingly logical (while still entirely dramatic) moniker of F-15 Global Strike Eagle, and it could have revolutionized how America deployed hypersonic weapons or put small payloads into orbit.

The idea was to use the Eagle’s powerful afterburning turbofan engines and the incredible amount of lift offered by its design to ferry rockets up to high speeds and altitudes before releasing them to ignite and fly the remainder of the journey into orbit. Launching orbital payloads from an aircraft would eliminate the need for expensive rocket launch facilities while making it possible for F-15s to rapidly deploy small payloads into orbit from anywhere on the planet with an airstrip and a hangar.

It was a relatively low-cost solution to a very expensive problem America’s military, particularly the Space Force, continues to tangle with today. But despite a very realistic approach to the Global Strike Eagle design, Boeing’s pitch likely still seemed a bit too crazy to put into practice… at least as far as we know.

The idea and its accompanying designs may look more like something Wile E. Coyote might build than anything to come out of Boeing’s brain trust, but the official proposal offers a number of startling conclusions about the feasibility of such an effort. In fact, although Boeing’s Global Strike Eagle never made it past the proposal stage, their data seems to suggest that a rocket-packing Eagle could actually work.

WHY THE F-15?

When the McDonnell Douglas F-15 Eagle first took to the skies in 1972, the stakes felt a lot higher than we can really appreciate today. Just five years earlier, American analysts had gotten their first glimpse of the Soviet’s newest and most capable fighter, a platform that evoked chilled whispers about broken speed and altitude records for years before any American had even seen it. Within the halls of the Pentagon, this powerful new fighter was known only by its prototype designation: the Ye-155.

But the United States and its NATO allies would soon have another name for their Mach 3 boogeyman: The MiG-25 Foxbat.

The Foxbat, America wouldn’t know for years to come, was more about propaganda than power, and while the MiG-25 would fail to live up to its reputation, the F-15 McDonnell Douglas produced to counter it would be everything America had hoped and then some. With a top speed in excess of Mach 2.5, a climb rate of more than 67,000 feet per minute, low wing loading, and a high thrust-to-weight ratio, America’s new Eagle became the game changer the Pentagon feared the Foxbat already was, and it would go on to prove it in fight after fight. Eventually, the F-15 would rack up an incredible 104 wins against enemy aircraft, and all without ever losing a single jet in an air-to-air scrap.

With the immense success of the Eagle, it wasn’t long before the U.S. began exploring other uses for their powerful and acrobatic new airframe. By 1986, just ten years after the first F-15s entered active service, flight testing began on the next iteration of the Eagle lineage; the ground-attack-oriented F-15E Strike Eagle. With the same pair of Pratt & Whitney F100-PW-220 afterburning turbofan engines pumping out a bit more than a combined 58,000 pounds of thrust and new hard points and avionics to support a broad variety of conventional and even nuclear payloads, the Strike Eagle quickly followed in the Eagle’s footsteps, making a name for itself as an attack aircraft with such potent air-to-air capabilities that it had no need for a fighter escort.

Over the span of the past 50 years, the F-15 has proven so incredibly capable that it’s been considered by the Navy for duty aboard aircraft carriers, been modified to take off at speeds at low as 42 miles per hour, been landed by a student pilot after losing an entire wing, scored an air-to-air kill with a bomb, and even nearly got the stealth treatment complete with conformal weapons bays. In fact, today, 46 years after entering service in the U.S. Air Force, brand new F-15s, dubbed F-15EXs, are still rolling off the assembly line and straight into Uncle Sam’s hangars.

F-15s have been chosen for plenty of other experimental efforts too, from launching hypersonic Phoenix missiles for NASA to literally shooting down a satellite, but as incredible (or even downright crazy) as many of these efforts may have been, they all pale in comparison to one 2006 Boeing proposal that aimed to mount a 45-foot-long, three-stage rocket to the Eagle’s back.

WHY ADD A ROCKET TO A FIGHTER JET AT ALL?

The first and most obvious use for an F-15 with a rocket on its back would be the rapid deployment of orbital or suborbital munitions like many modern hypersonic glide-body weapons, and indeed, mention of using this system to deploy America’s Mach 5 “Common Aero Vehicle” did make its way into the proposal. But the bigger benefit, Boeing seems to suggest, would be as a readily available, low-cost launch platform that could put small payloads into Low Earth Orbit from practically anywhere on the globe.

Despite a greater availability of space-launch platforms than ever before, America’s orbital efforts have long faced challenges related to launch infrastructure and the incredibly high costs associated with single-use rockets. But despite the waiting lists for launch complexes and the immense expense, America and most of the world continues to find itself more reliant than ever on space-based assets for everything from the operation of advanced combat systems to streaming the first season of “How I Met Your Mother.”

For the most part, these jobs are filled by large, complex, and expensive satellites in high geosynchronous orbits that take years to get from the designer’s pad to the launch pad. As a result, cutting-edge defense and intelligence satellites are often already outdated by the time they reach orbit.

“Today our satellites are very exquisite. And they’re the world’s best but they’re not cheap, and they’re not something that we can procure overnight. They take time to acquire … We put a lot of mission assurance on it, which then drives increased costs and increased timelines, because you can’t take the risk of failure,” Gen. John “Jay” Raymond, chief of the U.S. Space Force, explained last year.

In the United States, Cape Canaveral Air Force Station sees the majority of large American launches aiming for a West-East orbit, while Vandenberg Air Force Base in California is America’s primary gateway to North-South orbits. These facilities are designed specifically to manage large rockets carrying heavy payloads, but the U.S. also uses contractors and international partnerships to launch payloads aboard smaller rockets from facilities the world over.

Related: Silent Eagle: Boeing’s plan to make the F-15 a ‘stealth’ fighter

America’s “exquisite” satellites are extremely vulnerable

The lengthy timelines associated with deploying new satellites aren’t just a problem for observation and deterrence. Were a conflict to break out between the United States and a near-peer opponent like Russia or China, America’s fragile satellite infrastructure would be among the first targets. Both Russia and China have demonstrated the ability to engage satellites with kinetic weapons, and in recent years, both have deployed “inspector” satellites capable of grabbing, interfering with, or destroying other satellites in orbit. Russia has secretly deployed and tested weapons in space before, including a cannon, and it stands to reason that these nations may have orbital assets the general public is unaware of.

Unfortunately, many of the satellites America’s defense apparatus relies on were designed and built in an era when space-based conflicts seemed more like science fiction than the disconcerting reality of today.

“We built exquisite glass houses in a world without stones,” former Secretary of the Air Force Heather Wilson explained about the vulnerability of America’s satellite infrastructure in 2018.

So, to put a fine point on it, America’s commercial, defense, and intelligence sectors all rely on a constellation of extremely expensive satellites that take years to design and build, cost a fortune to launch, and are extremely vulnerable to attack. It’s the perfect recipe for a very bad day, and that’s exactly why the U.S. Space Force was founded with satellite security and redundancy as one of its primary goals.

In order to help accomplish this mission, the Space Force is placing a new focus on quickly fielding a much larger number of smaller, cheaper satellites that would fly in Low Earth Orbit to supplement the bigger, more expensive platforms. These satellites could fill gaps created by damaged satellites, provide rapid communications or intelligence information in areas that would otherwise be very difficult to do so, and even help to locate the sources of radio frequency jamming that’s interfering with access to those higher-flying and more capable assets.

But in order to leverage this approach amid a large-scale conflict with a technologically capable opponent, America needs a method of getting a high volume of small satellites into Low Earth Orbit very quickly and from locations all around the globe.