Given the spectacular special effects on display in Marvel’s “Iron Man” movies and the Defense Department’s clever allusions to the popular hero throughout the development of programs like their TALOS armored exoskeleton, you could be forgiven for thinking mankind is on the cusp of fielding some real-life superheroes. Many media outlets have been happy to latch on to reports of progress made on the Pentagon’s exosuit efforts, running headlines suggesting special operators will soon be tooling around in super-strong, bulletproof power-armor suits that will completely change the way combat operations are conducted.

It’s an exciting prospect, but realistically speaking, these reports of special operators fielding Iron Man-style suits on near-future battlefields are almost as fictional as the comics in which Iron Man can be found.

“When we get the exoskeleton here in a few months, we will have the best exoskeleton in the Department of Defense,” explained SOCOM Acquisition Executive James Smith earlier this week. “It will not be something our operators will feel comfortable putting on in a close [combat] environment today. So, moving, shooting, communicating in the face of enemy fire—not quite there yet.”

For the sake of emphasis, let’s revisit that last sentence one more time: “So, moving, shooting, communicating in the face of enemy fire—not quite there yet.”

The TALOS suit may not be the only exosuit under development in the Pentagon’s varied tool box, but it is, by most accounts, the most advanced and combat-centric. Back in 2013, the Defense Department even released this hype video that—it’s fair to say—could compete with the Kremlin’s work in terms of propagandized claims of “near-future” capabilities.

Now, however—six years of development later—the TALOS suit still lacks the ability to move, shoot, or communicate. What gives?

The truth is, as simple as Tony Stark makes it look, developing a truly functional combat exosuit is an extraordinary undertaking. Not only does it require developing new and advanced technologies, but it also requires those technologies to mature to a sufficient extent as to make them extremely reliable. It isn’t enough to build a TALOS suit that can survive a single engagement. To make the concept truly feasible, the suit has to be resilient enough to survive the extreme operational tempo of today’s special operations community. The suit needs to fire up and function day in and day out for months on end, in the most extreme and dangerous circumstances imaginable.

The very concept of the suit invites some difficult questions. In the minds of most ballistics experts, bulletproof isn’t a real thing; only bullet resistant is achievable. That differentiation is important when building equipment for combat operations: Even the mighty M1 Abrams tank isn’t considered bulletproof. It would just take one hell of a projectile to puncture the 600mm of armor adorning the front of it. Truly bulletproof armor plating of the thickness employed by Tony Stark’s Iron Man suit simply doesn’t exist, so systems like TALOS need to rely on a trade off between ballistic protection and maneuverability. Put simply, if you cover the suit in enough armor to stand and eat rounds, it becomes extremely heavy and immobile. If you build it to be able to move quickly and with enough agility to do things like dive behind cover, it will require either less armor or more power.

That need for power is a serious issue for these endeavors. It takes a lot of energy to move a giant armored suit around at all, forcing the suit to rely on either a huge store of batteries (which increases load and adds to the power requirement) or a fuel-powered generator that would compromise any form of stealth the suit would offer. Just imagine preparing to breach during a nighttime raid when the gas generator on your exosuit kicks on. So much for the element of surprise.

So in order to make these suits feasible, the Pentagon needs a small but potent power source, or far better batteries than we may be capable of producing currently. The suit needs to offer more agility than existing technology allows, and it needs to do so while demonstrating better reliability than a Toyota Camry, despite being used in only the worst and most dangerous conditions on the planet.

So how long will it be before we start seeing the 160th’s Little Birds being retired in favor of JSOC teams running in while dressed like War Machine? Optimistically, you could say years. Realistically, we may really be looking at decades.