Any planet, or the moon, where a jetpack would be practical?

For our space explorers once we figure out how to get them there. Due to lower gravity of mars, the moon, lets throw in Pluto also and ignore how cold it is and how far, would a jet pack be a practical means of getting around, perhaps superior to a moon rover/buggy?

Practical by what standard? It would probably be more practical than, say, a Segway, but given the minimal amount of cargo capacity and limits to range and duration, it wouldn’t take you very far or in much comfort.

And you say “jet pack” implying an air-breathing turbojet or turbofan engine, but of course in a near vacuum condition such a system wouldn’t work, and even in an environment with an oxygen-poor atmosphere you’d need to provide an oxidizer rather than extract it out of the air. In such conditions you’d need to use a rocket engine powered by either hot gas (combustion) or cold gas (stored pressurized gas) both of which are not very mass efficient compared to any ground vehicle.

Stranger

I wonder if a jetpack would work on Titan? Only in that case, it would be oxygen that was stored in the jetpack and it would work off gaseous hydrocarbons in the atmosphere.

Stranger : what if there was a massive underground dome-shaped Luna colony. Something several kilometers across. As a side note, a mega-cavern like this would be more practical in that it would take less construction materials for structural reinforcement in the walls than it would on earth, right? (like 1/10 as much since 1/6 gravity and less weight from the reinforcing structure itself, right?). I mean, sure, building it wouldn’t be possible today, but robots could in principle do the outdoor construction portion.

Anyways, you could use a kerosene burning jet-engine driven jetpack, right? And it could be a vastly smaller size and given you hours of flight time. I’m talking about something like this.

Or you could use an electric fan jetpack, driven by lithium ion batteries. With something like 10 times the battery life(because you have a smaller weight to lift, and adding more batteries doesn’t increase power draw nearly as much) it might give you acceptable flight times.

Sure, don’t use it outside. Just a fun toy for indoors.

Someone’s been reading Heinlein’s the Menace from Earth.

I don’t see why some sort of personal reaction engine wouldn’t be useful in low-gravity situations, like Phobos (g local = 0.0057 m/s) or Deimos (g local - 0.003 m/s) or asteroids. After all, it’s not that different from, say, the Gemini IV spacewalk, where the Ed White’s Hand-Held Self-Maneuvering Unit has just a miniature reaction device.

At those gravities you can probably achieve escape speed just by jumping. I wouldn’t really consider an MMU a “jetpack” in the sense of transportation; it’s primary function is just allowing you to maneuver at all in a low gravity field in which you can’t use gravity to generate a useful amount of friction or resistance.

Stranger

In any reasonably strong gravity, a rocket powered jet pack ain’t much. On Earth you might get a minute or two of hovering. Lower the gravity and your time limit goes up. But no matter how you slice it your time is limited and or you are just basically moving around in for all practical purposes a zero G environment.

Now, if you use a small jet engine(s) (which they make these days) AND are in a lowish G environment (that has dense atmosphere you can use) you could probably get enough time out of such a system to be considered extended fun / marginally useful.

Randall Munroe said you could strap on wings and fly under your own muscle power on Titan, and it probably wouldn’t be any more taxing than walking around on earth. But I don’t think he factored in the weight of whatever you’d have to wear to keep yourself warm and breathing. Still, it makes it sound like your idea might be feasible. Methane and hydrogen gas do make up about 1.6% of Titan’s atmosphere… how reactive is oxygen and methane / hydrogen at 72K?

Isn’t the big problem with jetpacks frying the backs of your legs with the exhaust?

“Jetpack” is mostly a cartoon / SF idea for a technobabble-powered levitation device. Specific implementations could be almost anything

Actual Earthbound implementations have been few and far between. Some of those use expanding pressurized gas. Those have very cold exhausts. Others have a chemical reaction (not combustion) that produces heat alongside the desired expanding gases. Those have hot exhausts.

The exhaust of a device designed for use on Titan or Phobos? Imagine away.

I’d go with a hydrogen peroxide and silver catalyst jet to eliminate the need for atmospheric oxygen.

Hydrazine with an iridium catalyst is also good. With bonus points for extra toxicity of both the fuel and the exhaust. https://en.wikipedia.org/wiki/Hydrazine#Rocket_fuel

You rocket folks are missing the point. An air breathing engine has WAY more thrust per unit of thrust/fuel consummed than any kind of rocket/self contrained thruster system. Like 10X more.

Which is why about the only things that are rocket powered are rockets.

The Asteroid Belt could be a place where a pack might be useful.

How about in the rings of Saturn? Could you go from rock to rock, or would they still be crazy far apart?

Granted.

But lots of places with very low gravity have no atmosphere. The low gravity means you don’t need much thrust to fight it. And the no atmosphere means the “jet” in “jet pack” can’t mean air-breathing turbojet or variant thereof. Which leads to the conclusion that A) rockets are the only choice; and B) they just might work well enough despite the terrible fuel specifics.

Very few “jetpacks” have ever flown on Earth. And AFAIK they’re all really rocket packs with a misleading popular name.

On the other hand, there’s the intermediate case of if there is some sort of atmosphere around you. Then even if you need to carry both fuel and oxidizer for a jet engine, it still gives you more thrust than a pure rocket engine thanks to using the atmosphere as reaction mass.

Interesting cite (plus I never knew about the photo of Titan’s surface).

But it made me question/wonder about “flying” in any atmospheric zero-g using muscle power, vs. jet pack, vs. grabbing on rails and projecting yourself around town, which is the way the guys in the ISS do it.

Just as the power efficiency of O2 combustion vs. rockets is analyzable, so should metabolic expenditure, all depending on performance regime in question.

NASA actually studied the idea of a ‘lunar rocket pack or chair’ for use in exploring the Moon in the later ‘J’ missions of Apollo. They settled on the Rover instead.