>It takes a lot of fuel to do anything in space.

No it doesn't. It sometimes takes a lot of fuel if you're too impatient to wait for gravity to do the work for you.

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>Why do we assume aliens have similar technologies or more advanced technologies than we do?

We don't assume that.

What goofy-ass sources gave you that impression?

How do you know they aren’t fake, or disinformation, or misinterpretation of information? Because “highly official” Air Force guys say so? The whole recent wave UAP shit is suspicious af and more than likely “not aliens” and just some US government bullshit distraction stuff.

>Avatar is probably one example

You're not sure if Avatar is an example of humans meeting a less-advanced species?

Funny, I just finished a re-read of John Varley's novel Red Thunder that has this exact scenario in it. Granted, it is a completely made up technology that they use to achieve the unlimited thrust, but still fun to see how they handle it. Really good sci-fi read. Btw, they made the trip to Mars in three days at 1g.

Daedalus was still an Orion-esque engine, but with thermonuclear (not fission) 'devices'.

Bussard ramjets are out of favour as nobody is sure that they make nett thrust.

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You just trolled the hell out of a couple people.

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This is also how space travel works in the Expanse series. Typically they travel at 0.3g to save fuel (plus a few other reasons) but it makes most tasks relatively the same

I think it was Daedalus that used the scoop. Orion used the pusher plate nukes.

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You are welcome...Baphomet.

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...Thanks? Satan?

Exactly. No one thinks all intelligent life is more intelligent than us, they think any that has managed to travel to earth would be, and probably so regardless of how long it took them to get here.

Short answer is that we don't assume that. Not sure if you've heard of the fermi paradox but the solutions proposed to that seem pretty relevant to what you're asking here.

Long answer is simply that we don't think that but that our discussions typically revolve around advanced civs because they pose the most interesting and relevant discussions to our world today. We only talk about more advanced civs because the types of aliens relevant to our own interests and security would probably be advanced. A hunter-gatherer civilization probably wouldn't be a threat, we wouldn't be able to communicate with them from long distance, and they wouldn't visit us here on earth so we just don't talk about them as much. Scientifically speaking, aliens could be anything, but we just don't know. Your discussion above is one of many possible conditions of extraterrestrial life.

If they're less advanced, how'd they get here? I'd love to see some of your sources.

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Wasn't project Orion a really bad idea version of this? But I think the fuel scoop was the only missing technology?

Nuclear engines tend to be both heavy and have low thrust, which mostly cancels out the Isp advantage.

You know how to get to Minmus don’t you?

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I see what you're saying, and it does make sense.

However, think of the great achievements made during the Greek, Roman, Egyptian empires, as well as the Chinese Dynasties, etc. And now add to that, people like Galileo, Isaac Newton, Francis Bacon, who added so much to science without an industrial revolution.

Beings with more intelligence would arrive at those mathematical principles that Newton arrived much faster perhaps? I am sure there might be other life forms out there much smarter than us, and that alone perhaps could make an industrial revolution irrelevant for their space exploration.