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This is great sci-fi fodder, imagine if you could land a tiny craft on that thing and then use the hydrogen as fuel without having to haul all that fuel into de
by fenwick67 6y ago
This is great sci-fi fodder, imagine if you could land a tiny craft on that thing and then use the hydrogen as fuel without having to haul all that fuel into deep space (very unlikely to be practical but the idea is exciting).
- diroussel 6y agoThen the problem becomes getting oxygen. As a hydrogen won't burn in a vacuum.
- ISL 6y agoUnless you can fuse it into helium.
- throwaway2048 6y agoIf you have the tech to fuse hydrogen the amount of fuel you would need for a nearly unlimited amount of energy is tiny, you would save very little by harvesting it off a comet/asteroid.
- jandrese 6y agoDepends on how much energy you need. If you are talking about turning it into an interstellar spacecraft by hooking up some kind of fusion powered thruster (probably using H2 as the reaction mass) to the back you may need all of its mass. This is of course well beyond our current capabilities, but it's not something that's impossible to consider in the medium-distant future. Plus, even if you expend a colossal amount of energy accelerating you're still talking about thousands of years for the journey where you'll need to keep those reactors running for the entire trip (there is no useful solar collection in deep space) having a literal mountain of fuel to start with is important.
- Sharlin 6y agoYou still need propellant mass. Energy in itself doesn't get you anywhere. But in practice you'd probably be better off electrolyzing water ice which is ubiquitous in the outer Solar System.
- scotty79 6y agoUnless you just want to colonize this hydrogen iceberg, and live on it for next thousand years, recycling all other elements indefinitely as you cruise through the galaxy.
- rfreytag 6y agoInsulating the fusion reactor from the solid hydrogen in Oumuamua could prove difficult.
- masklinn 6y agoPut Oumuamua at the front? It's not like drag is a concern.
- sawjet 6y agoI could still be useful as a propellant for say, a nuclear thermal engine.
- btilly 6y agoMatching speeds with it for this operation would take much better rockets than we have available.
- valuearb 6y agoA Starship sized vehicle using the well tested NERVA engine would be able to add around 20 km/sec to the velocity it already has in earth orbit. So pretty close and gravity assists would increase that. Once you dock with Oumuamu, you can run it’s material through at an 890 ISP and gradually accelerate to much higher speeds.
- btilly 6y agoYou underestimate the problem. First you have to add something like 40 km/sec to go from Earth orbit to escape into interstellar space, and then you have to add another 20 km/sec to match speeds with Oumuanu. That's 60 km/sec, which is 3 times the speed and takes 9 times the energy. Pioneer and Voyager got to interstellar space with gravity assists. But those work best when you barely get to a planet's orbit, then it picks you up and you go close to 180 around it. (Thereby adding 2x its velocity to your own.) Once you start getting to the velocities needed for Oumuamu, you just shoot by the planet and don't get much of an assist. (Assuming, that is, that there is an alignment between the planets and a random interstellar visitor. Which is extremely unlikely.) I stand by my statement. We do not have good enough rockets for this maneuver.
- koheripbal 6y agoI think the theories of it being an artificial alien probe were definitely more sci-fi fodder. I'd always imagined that an alien intelligence might have seeded every solar system in the galaxy with a probe to monitor for evolving intelligence - but after Oumuamua, I realized it would be far more efficient and reliable to have swarms of them coasting through systems periodically to check on them. ...or maybe both.
- aj7 6y agoOr just follow it.
- Symmetry 6y agoYeah, though there's lots of water in the outer solar system you can get your propellant from. The term to google is In Situ Resource Utalization (ISRU). https://en.wikipedia.org/wiki/In_situ_resource_utilization https://en.wikipedia.org/wiki/In_situ_resource_utilization
- LeifCarrotson 6y agoBut those are mostly just orbiting the sun. If you ever wanted to send a probe to Proxima Centauri, and stop when it got there, accelerating the fuel you'd want to have available to decelerate up to solar escape velocity would be a tremendous energy expenditure, even if you can mine it in the asteroid belt. If, instead, you got lucky and jumped your probe (fuel tanks dry) on an interstellar wanderer that happened to be going approximately in the direction you wanted, you could have hundreds of tons of rocket fuel moving at interstellar velocities.
- detritus 6y agoTrue, but those interstellar velocities are mercilessly pitiful in respect to much of use there.
- motoboi 6y agoImagine you just land a tiny craft on that thing and let the thing take you to interestelar space without you having to burn no more fuel. Unfortunately, if you can't catch it, you don't need it for that, as you'll be traveling faster that it to be able to intercept it and would just burn fuel trying to break enough to match its speed.
- TeMPOraL 6y agoRule 1 of orbital mechanics: if you're about to dock with something, you're already on the same trajectory as that thing. Might make a good radiation shield, though.
- ragebol 6y agoI'm not into orbital mechanics at all, just an interested layman, but how does a space tug work in relation to your 'Rule 1 of orbital mechanics'?. What is the point of a space tug then?
- hjb 6y agoThe space tug is there to change the trajectory of the other thing: 1. Tug gets in same position and velocity as its target, and docks. 2. Tug performs some kinda of burn to put both it and its target on the new trajectory. 3. Tug undocks and performs a burn to head off to where ever else it's needed. If I understand correctly, it's really just a way to avoid putting engines and fuel tanks on things that don't need to change trajectory much.
- marcusverus 6y agoThe space tug and its load / target are on the same trajectory at the time of rendezvous. Once they're synced up, they're drawn toward each other, with the tiny gravity of each affecting the trajectory of the other. But while the load is passively traveling through space, the tug can reposition itself. This way, the tug determines the ultimate trajectory of the load while also having some control of its own trajectory, which it uses to continually bend the load's trajectory.
- rbanffy 6y agoIt'd be fun to operate a nuclear-thermal rocket for decades, heating the ice and piping it through the reactor and out the nozzle.
- lmilcin 6y agoYeah, imagine you have whole lot of hydrogen and no oxygen to get it to burn. You are going to freeze to death while moving nowhere. About the only good thing it could be used for is reaction mass. But you can use almost anything as reaction mass as long as you have a source of energy, you can exhaust any particles to propel yourself forward, doesn't have to be hydrogen.
- marcosdumay 6y agoIf it's only hydrogen, you can still fuse it. Well, not today, but we can't reach it today either.