The jetpack is the consummate icon of the early years of science fiction. This device represents the ultimate in convenience and personal mobility. Just strap this backpack-sized object on and travel anywhere you'd want to go. Never mind the actual technological challenges in making such a device practical.
However, the standard depiction of the jetpack in media has one problem: The proximity of the jet exhaust to the seat of the pilot's pants. Without some Unobtainium-level heat protection, the pilot's rear, thighs, and possibly calves would get charred to carbon within minutes (or seconds) of firing the thing up. Yet going back through all the rocket man serials of the 1930s and the homages to them, we see no attempt to shield the Jet Pack operator from this simple operational hazard.
This issue is likely ignored for the same reason that no-one ever calls anyone on Convection Schmonvection: If the flames aren't visibly in contact with the pilot (or visible at all in the case of certain combustible gases), then "obviously" there'll be no harm. An actual technical way of avoiding this trope, of course, would be to have the thrusters mounted by the shoulders and/or pointing outwards with the thrust directed away from the user's body.
- Chachamaru of Mahou Sensei Negima! sprouts a jetpack from her back in this manner. Though she herself is undoubtedly resistant to heat, her standard-issue school uniform always remains unsinged (might also be a case of Magic Pants since the jets appear through her blouse and blazer).
- Averted in Digimon Savers. Gaomon and Agumon get jetpacks as part of their evolutions to Machgaogamon and Rizegreymon, respectively. The former gets the jet part at the ends of the wings, while the latter has jets as part of the wings (and point away from his tail).
- Lampshaded in an early issue of West Coast Avengers, where Wonder Man debuts a new (and hideously ugly) costume, with his trademark jet thrusters moved to his back instead of his hips.
Tigra: Won't that burn your... ah...
Wonder Man: Not if your "Ah" is invulnerable.
- In Ex Machina, this is a problem for "The Great Machine" once or twice. But that's why his backup always has fire extinguishers.
- Gaston Lagaffe designs a jetpack but Reality Ensues when he tests it, burning up his ass and making him run around screaming in pain. After turning off the fire, Fantasio remarks that while it doesn't do much vertical performance, it does a lot of horizontal performance.
- Exploited in one installment of MAD Magazine that had a comic strip showing a pilot being sent to a hangar to report to the base's local Mad Scientist. The scientist tells him he's overqualified and gives him a jetpack, and is told to arch his back. The pilot was actually meant to test a pair of bionic legs.
- Averted with Paperinik's old rockets (dating back to the earliest classic stories): they're placed on the sides of his belt; thus they avoid toasting his butt and setting his cape on fire. Justified as Gyro used that rocket belt for a while before giving it to Paperinik, hence he had plenty of time to work out any flaws.
- Used for Paris/Kim Slash Fic in Captain Proton's Blistered Buns.
- Captain Proton and the Planet of Lesbians. When Captain Proton has to give an Action Girl a lift with his jetpack, she complains the control knobs are digging into her breasts. Proton retorts, "You think you've got problems? My ass is being roasted like a Christmas turkey!"
- The movie Batman: Mask of the Phantasm shows the Joker using a jetpack with exhausts on the shoulders.
- Averted in Transformers: Revenge of the Fallen: The thrusters on Optimus Prime's Powered Armor are outboard of the shoulders. They can also pivot, as Optimus demonstrated when he weaponized the backblast against Megatron.
- Spoofed in J-Men Forever when a Gag-Dubbed Commando Cody complains that his feet are on fire, along with the many other problems of using an atomic-powered jetpack.
- The Rocketeer tries to Hand Wave this by suggesting that the alcohol-based fuel will result in a cooler flame (which is true)— but said fuel will not produce nearly enough energy. Points for trying, though. In fact, the Rocketeer is flat-out bizarrely inconsistent about this — in one scene, the jets set fire to the set, but in another a sheet is directly exposed to the flames for several seconds without even being singed.
- Minority Report has the protagonist fighting a jetpack-equipped police officer inside an apartment. Oddly enough the exhaust flame does set a few other things on fire, but leaves him miraculously unscathed.
- Star Wars: Boba and Jango Fett. Though they are wearing what is likely heat-resistant armor. Averted by other Mandalorians in the EU, who make use of a skirt-like Kama, which is made out of flame-retardant materials to protect their legs.
- Averted in Thunderball, which has a real frickin' jetpack, with the nozzles well clear of the body. (Though the sound effect was changed because Reality Is Unrealistic).
- In RoboCop 3, the title character kills the villain by burning his legs with the exhaust of his Jet Pack, leaving him helpless in the soon-to-explode building.
- Subverted in the Marvel novel Codename: Wolverine. S.H.I.E.L.D. is testing just such a jetpack, with the S.H.I.E.L.D. agents wearing a special heat-resistant bodysuit when using it, though tests are brief so far since the reliability is questionable. Wolverine dons the pack so he and Mystique can make their escape (with him sans suit), and gets to put his healing factor to yet another very painful test.
- Actor Robert Duncan McNeill recounted at a recent Con of his time as Tom Paris on Star Trek: Voyager that his rear did catch fire from the jetpack in a "Captain Proton" episode. The on-site nurse had him drop pants right there to make sure everything was all right. He claims Tim Russ has photos.
- At least approached in Upright Citizens Brigade episode "The Story of the Toad", in which Antoine asks two prostitutes, "Hey... How would you ladies like to make love while wearing a jetpack?" but then cautions, "We can't do it doggy style though, you'll set me on fire."
- Handwaved on Buffy the Vampire Slayer with Warren and Andrew's jetpacks. They popped out of backpacks on scissor-like extenders to prevent the trope but would have probably ripped themselves off their mounts if they really had enough thrust to lift an average human into flight.
- Deadlands hand waves this trope in its Mad Science source book, "Smith and Robards": every jetpack purchased is shipped with a complimentary pair of asbestos pants.
- Warhammer 40,000:
- Averted by the jetpacks used by Space Marines and Sisters of Battle, which are built so that the exhaust flies outward at an angle from the body of the flier. Their legs are nowhere near the danger zone. Being clad in Power Armor probably helps too. Grav-chutes used by the Imperial Guard have a similar design, though they are less powerful and are used only for descent.
- Ork jetpacks are brutally utilitarian, consisting of a missile without a payload (or sometimes with, they're not picky), and the toasting becomes a non-issue due to their comedic superhuman toughness (they can survive decapitation if there's a dok around to stitch them back up).
- Mechwarrior, BattleTech's spinoff roleplaying game, features jump packs and jump infantry, who are explicitly stated to have fire retardant armor padding in their rear portion. Troopers in heavier Power Armor have jets integrated into the exterior of their battle suits separated from themselves by several inches of ablative armor, and thus don't have this issue at all.
- Averted/Subverted in the Kirby games with the Jet power. While it doesn't set Kirby on fire, it will toast everything around him.
- Averted in Mega Man. Rush turns into a jet platform as he's built for the purpose of being transportation. 6 and 7 have the thrusters outboard of the shoulders on the Jet and Super armors, respectively. Also, characters with built-in flight usually use wings or a rotor system to fly. In the Mega Man X series, flying bosses use wings or leg mounted jets. Even if characters have back mounted jets, those point out from the back, not towards the ground. Being robots that are constructed in a way that they operate fine in snow, underwater and Lethal Lava Land doesn't hurt either.
- Star Wars: Shadows of the Empire: once you reach the Gall Spaceport, you can find a Jetpack with the exhaust directly over Dash Rendar's butt.
- City of Heroes has plenty of jetpacks. Some follow this trope, others avert it by having the jets spaced away from the body.
- Possibly averted in most of the Duke Nukem games, where Duke's jetpack doesn't appear to blast anything dangerous out of the bottom. From the noise and lack of flame, it would appear Duke's jetpack is more of a ducted-fan type of thing rather than any sort of combustion engine.
- Kingdom of Loathing. Lampshade Hanging in the item description for the toy jet pack:
It's of the "concentric rings of energy" build rather than the "gouts of flame" build, so at least it won't singe your butt when you go flying.
- Averted, though perhaps partially used in the game Cortex Command. Soldiers with jetpacks have the exhaust come out just below their butt, which might normally singe their legs. But, they automatically bring their legs forward when jetting so their legs won't be burned off. There are two downsides: first, if you try to use the jetpack while landing, the solider might fall on its torso rather than feet, resulting in more damage, so the last second before touchdown needs to be jet-less. Second, the game's designers haven't yet made a separate "kneel" animation, so when you try to kneel, the soldier puts his legs in front of him like he's just waking up from bed, and it looks silly.
- Averted in the game Soldat, since you have rocket shoes rather than a jetpack.
- Also averted with The Fury's jetpacks in Metal Gear Solid 3, in which the boosters are outboard on his shoulders. One thing to note: it's rocket-fuel powered. By the way, his flamethrower also uses rocket fuel.
- Averted in Outwars; the jetpacks have the nozzles rotated by 45 degrees so that they can't possibly hurt the operator. The way this is depicted is not perfectly logical, as such an orientation would waste half the power of the pack attempting to move the operator horizontally against itself, but it's still better than having your lower half vaporized... The jetpacks aren't necessarily for flying; they're used for slowing falls. True horizontal flight requires an experimental glider-wing that folds neatly into your pack.
- Weaponized in Tatsunoko vs. Capcom, where about a third of the PTX-40A's normal attacks involve roasting his opponents with his thruster-fire.
- Jetpacks tend to avert this in Halo; the thrusters are usually placed around the shoulders, to the side, and/or pointing away from the user. It also helps that the soldiers who use jetbacks tend to be well-armored.
- In World of Warcraft, for the airship battle event in Icecrown Citadel, players may equip themselves with jetpacks that allow flight to the opposing faction's airship. These jetpacks appear to operate in the traditional "toast your buns" fashion, and even get their lack of safety lampshaded by the dialog of the player accepting them. But what's particularly hilarious is that Druids can equip them while shapeshifted into Dire Bear form, resulting in a bear with a jetpack literally strapped to its butt. To quote a video that parodies this: ROCKET BARE! BURNIN' OUT HIS FUSE OUT HERE ALONE!
- In 007: From Russia with Love, jetpacks can literally solve all your problems - they're equipped with missiles, can hover on the spot, are easier to maneuver that actually walking - and are readily accessible at many points in the game. Nobody wears flame-retardant armour in the game.
- Averted in Grand Theft Auto: San Andreas by a simple use of actual design of Bell Rocket Belt that has exhaust pipes moved away and to the side of pilot's body.
- Averted in the Ratchet & Clank games, as Ratchet has flown Jetpacks, Thruster Packs and Levitators and not once burned his fur off.
- Subverted in The Adventures of Dr. McNinja as Doc meets a man using a jetpack and immediately tries to treat his leg-burns. Apparently, the dinosaurs who sponsor the whole jetpack thing (it really does make sense in context) deliberately use this style, as they are hunting the humans and aren't particularly concerned about their well-being.
- Averted with John's Rocket Pack, which is so large that it extends to the floor, and the exhaust comes out below the feet.
- But then played straight with Terezi's Wing Pack, which has the engine in the usual rump-roasting place.
- Then you get the cyborged Spades Slick, whose posterior is the jetpack.
- xkcd: Discussed in a comic, providing the page image. "Rocket packs are easy. The hard part is inventing the calf shields." The Alt Text for that comic is "Every year: 'It's <year> — I want my jetpack [and also my free medical care covering all my jetpack-related injuries]!'"
- My Life as a Teenage Robot, though Jenny's robotic body might just be heat-resistant.
- Dastardly and Muttley in Their Flying Machines, episode "Plane Talk".
- Subverted in The Venture Bros., where #24 takes off in a jetpack of the bottom-roasting sort (although it does have a plate that covers the length of the flames coming out), and off screen says 'My shoes are on fire! I just lit my shoes on fire!'
- Played with in Ed, Edd n Eddy. The episode "In Like Ed" features a prototype jetpack made by Edd that has its exhaust (which apparently jets out baking soda) go out above the shoulders; however, it still leads to Ed having an accident.
- Averted in Roughnecks: Starship Troopers Chronicles, where the jets are mounted on heatproof Powered Armor, and used only for landing (slowing the fall rather than actually flying) after a drop.
- Aversions in Batman Beyond, and Static Shock: Both Terry and Richie have jets, but they're mounted on their feet, rather than their backs.
- Brought up in El Tigre, where Manny rejects Black Cuervo's We Can Rule Together offer with a jetpack for incentive. (Which Manny really, really wants) As Cuervo flies off, Manny tries to console himself by talking about this trope.
Cuervo: There's a cooling fan!