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Oumuamua may be a hydrogen iceberg

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Re: Oumuamua may be a hydrogen iceberg

#51

Post by ragebol »

TeMPOraL wrote: post #47
motoboi wrote: post #42

Earlier quoted context omitted.

Imagine 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.

Rule 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.

I'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?

Re: Oumuamua may be a hydrogen iceberg

#52

Post by LeifCarrotson »

Symmetry wrote: post #37
fenwick67 wrote: post #3

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).

Yeah, 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

But 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.

Re: Oumuamua may be a hydrogen iceberg

#53

Post by hjb »

ragebol wrote: post #51
TeMPOraL wrote: post #47

Earlier quoted context omitted.

Rule 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.

I'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?

The 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.

Re: Oumuamua may be a hydrogen iceberg

#54

Post by marcusverus »

ragebol wrote: post #51
TeMPOraL wrote: post #47

Earlier quoted context omitted.

Rule 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.

I'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?

The 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.

Re: Oumuamua may be a hydrogen iceberg

#55

Post by messe »

saberdancer wrote: post #44
jamestimmins wrote: post #33

"It has now passed beyond Saturn’s orbit and will travel another 10,000 years before exiting the system". How big is our solar system? I always assumed it referred to everything between the sun and Pluto, but 10,000 years suggests it's far larger.

I'm not sure of what definition they used here, but one that is common is heliosphere, or in other words sphere around the Sun where solar wind is dominant. This is about 120 AU.

Could be the distance at which the sun's gravitational influence is comparable to that of the surrounding stars. This would vary over time, but as a rough estimate it's probably alright.

Re: Oumuamua may be a hydrogen iceberg

#56

Post by moron4hire »

BurningFrog wrote: post #49
motoboi wrote: post #42

Earlier quoted context omitted.

Imagine 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.

You can imagine intercepting a thing like this (Oumu has left the building), and hooking elastic rope to it to get dragged along. Seems like a real hard mechanical problem, but not fundamentally impossible.

Spacehook ala Skyhook https://www.cia.gov/news-information/featured-story-archive/...

Re: Oumuamua may be a hydrogen iceberg

#57

Post by detritus »

LeifCarrotson wrote: post #52
Symmetry wrote: post #37

Earlier quoted context omitted.

Yeah, 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

But 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…

True, but those interstellar velocities are mercilessly pitiful in respect to much of use there.

Re: Oumuamua may be a hydrogen iceberg

#58

Post by fenwick67 »

motoboi wrote: post #42
fenwick67 wrote: post #3

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).

Imagine 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.

Pfft, you can just lasso it

Re: Oumuamua may be a hydrogen iceberg

#59

Post by walrus01 »

ragebol wrote: post #51
TeMPOraL wrote: post #47

Earlier quoted context omitted.

Rule 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.

I'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?

One of the purposes of a proposed 'space tug' is to use slow low thrust but high delta-v, high efficiency engines to do things such as:

Raise the orbit of satellites in LEO which are affected by atmospheric drag. Or re-boost things like the international space station, proposed future Chinese space station, etc.

Extend the lifetime of geostationary satellites which are still electrically functional, but out of station keeping propellant. One such thing docked for the very first time with a satellite earlier this year. https://en.wikipedia.org/wiki/Mission_Extension_Vehicle

On unmanned missions, slowly move cargo from low earth orbit to destinations at the Moon or Mars. If you can use ion and hall effect type thrusters for your missions to move cargo around, you can establish a logistics supply chain for essential supplies consisting of unmanned craft.

https://en.wikipedia.org/wiki/Delta-v_budget

https://en.wikipedia.org/wiki/Specific_impulse

An interesting example of using ion engines to maintain low earth orbit, through long continual thrust was this mission:

https://en.wikipedia.org/wiki/Gravity_Field_and_Steady-State...

Re: Oumuamua may be a hydrogen iceberg

#60

Post by outworlder »

rrmm wrote: post #19
whatshisface wrote: post #15

Earlier quoted context omitted.

No, you can have zero momentum. However it comes along with having a position wavefunction that fills the whole universe.

Hey let's probe the boundary conditions of the universe.

Careful now, you don't want to crash the simulation.

It already slows down when you are moving too fast.

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