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Oumuamua may be a hydrogen iceberg

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Re: Oumuamua may be a hydrogen iceberg

#41

Post by tectonic »

idreyn wrote: post #8
sq_ wrote: post #7

Earlier quoted context omitted.

> Can you aerobrake around a star? Not a physicist, but it seems like you should be able to do something similar to aerobraking (not one-to-one since the Sun's "atmosphere" is different from a planet's). Maybe using a solar sail of some sort directed at the right angle?

I went on a wiki-binge on this topic a few days ago and so I recognize this as a magsail[0]. It would be an attractive addition to an interstellar craft since it obviates the need to carry propellant for deceleration. [0] https://en.wikipedia.org/wiki/Magnetic_sail

See also e-sail: https://orbitalindex.com/archive/2019-04-09-archive-Issue-7/

Re: Oumuamua may be a hydrogen iceberg

#42

Post by motoboi »

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.

Re: Oumuamua may be a hydrogen iceberg

#44

Post by saberdancer »

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.

Re: Oumuamua may be a hydrogen iceberg

#46

Post by mhh__ »

monadic2 wrote: post #2

Makes me wonder if you could slingshot around the sun towards relativistic speeds with thermal power. At the very least it could save fuel on the egress, if not the second half. Can you aerobrake around a star?

Can't do the maths at the moment but you'd probably need a lead spacecraft to get close enough. Getting close to the sun also means you'll be going ridiculously fast e.g. Parker Solar Probe will hit something like 200km/s and it's still millions of kilometres from the sun

Re: Oumuamua may be a hydrogen iceberg

#47

Post by TeMPOraL »

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.

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.

Re: Oumuamua may be a hydrogen iceberg

#48

Post by sailingparrot »

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.

But it would still take way less than 10000 years to cross the heliopshere boundary (it took 40 years for the Voyagers probes). It is probably referring to the gravitational sphere of influence of the solar system (marked by the Oort cloud) 1 to 2 light years away.

Re: Oumuamua may be a hydrogen iceberg

#49

Post by BurningFrog »

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.

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.

Re: Oumuamua may be a hydrogen iceberg

#50

Post by wahern »

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.

‘Oumuamua's incoming and outgoing speed is ~5AU/year. In 10,000 years that's 50,000AU, which is approximately the distance to the outer most region of the Oort Cloud: https://en.wikipedia.org/wiki/Oort_cloud
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