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trogon t1_jd109yn wrote

Yep, you could get to Mars in less than a week at 1 g, flipping halfway to decelerate:

https://space.stackexchange.com/questions/840/how-fast-will-1g-get-you-there

You're just going to need a lot of fuel.

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twohedwlf t1_jd10pr5 wrote

Yes, it would work, and you'd only need to flip once at the midpoint of the trip. But we don't have the technology now to maintain that kind of acceleration.

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twohedwlf t1_jd18c5k wrote

To give some idea of the amount of fuel needed. Say we wanted to JUST send a SpaceX raptor a 2 day burn(About the 1g time to Mars from u/trogon link) about 230,000,000 lbs of fuel and would start off at about 1/460th of a G acceleration. (Ignoring tanks, structural supports etc.) That gives an average acceleration over 2 days of 1/230th of a G.

So, you could never achieve it with combustion rocket engines.

Nuclear engines have much higher ISP, but only in the region of 2-3 times so they'd use roughly 1/3rd the fuel.

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Triabolical_ t1_jd1e0k4 wrote

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

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dasBergen t1_jd1fadc wrote

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

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BrentRedinger t1_jd1lye7 wrote

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

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Bipogram t1_jd1np17 wrote

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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collegefurtrader t1_jd15iru wrote

Yes, if you have unlimited fuel and/or energy.

Unlimited energy solves a lot of problems.

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No_Leader1154 t1_jd11cmu wrote

In the Tintin comic, “Destination Moon,” they do exactly this. The rocket is nuclear powered, maintains 1g acceleration until the halfway point where they flip and decelerate. Takes them only a few hours.

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Celebnar t1_jd1mhuz wrote

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

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OysteinM OP t1_jd11us7 wrote

Loved Tintin, did not know he had the same idea 😀

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the_hamturdler t1_jd0y72e wrote

Ive got 4G on my phone so I’m sure they can think of something eh

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OysteinM OP t1_jd0z2lg wrote

I was thinking about permanently 1G for the duration of the journey.

Have 5G on my phone, does not work well on Mars :)

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stewake t1_jd11iz0 wrote

It takes a lot of fuel to do anything in space. This would be a very inefficient use of something that is very essential elsewhere, and very heavy.

Also, nuclear engines are very efficient, yes. But they do not produce a lot of thrust, so it would be very difficult to sustain an acceleration that high.

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OysteinM OP t1_jd12oos wrote

I know, this was a thought experiment.

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ZylonBane t1_jd1qjl3 wrote

>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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AbbydonX t1_jd17m6x wrote

Accelerating at 1g for half of the trip and then decelerating at 1g for the remainder would certainly be a way to produce artificial gravity.

However, current (and future) propulsion methods either have high thrust or high specific impulse. This means you can only have 1g acceleration for a short period or much lower acceleration for an extended period of time.

Ships that can achieve continuous 1g acceleration are called torchships in sci-fi but unfortunately there are no predicted methods to produce them yet.

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PandaEven3982 t1_jd10way wrote

Please google the term "Aldrin Cycler" if you prefer it in sci-fi, The Last Dance by Martin Shoemaker.

Edit: I'm suggesting this because of current economics. We are a way off from the 1G continuous acceleration being feasible.

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ExtonGuy t1_jd16fm9 wrote

Sure, it would work. Where are you going to get the "unlimited power"? Not even nuclear power is unlimited. It could be used to produce heat, which would be used to kick something out of the rear of the spaceship.

You just need something 50 times the mass of the payload (including that nuclear heater). So 1 part living system & heater, and 50 parts reaction mass to kick out. Now, how heavy is a nuclear reactor that can heat water (or whatever you're using) to super hot plasma?

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sifuyee t1_jd19i4v wrote

Issues, poppycock! Nothing wrong with spinning. Just attach the crew section to the engine section via tether and let it reel out so they're far enough apart that it's not disorienting as you spin them like a set of bolos. 80% of the time it works every time.

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ElmoFromOK t1_jd1odts wrote

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.

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The_Solar_Oracle t1_jd1s2bg wrote

> . . . I've read that the spinning spaceship (Circular disc) will not be useful, because; issues

There's nothing that makes spin-gravity a show stopper unless the habitat in question is very tiny and rotating fairly quickly, but it's also not a strict requirement for a mission to Mars and that's why it's seldom considered in detailed plans for manned missions to Mars in the near future.

Assuming the slowest normal trajectory (assuming you're not using a very low thrust but still man-rated electric rocket), going to Mars or returning from it takes about eight and a half months. There have already been human beings that have spent more time than that in space within individual missions, and they also fully recovered from any negative effects.

There, however, remains a question mark in regards to how deleterious Mars gravity may or may not be towards the human body. It's quite possible that some gravity, however low, may be enough to stave off the effects typically seen with extended periods of living in zero gravity. Very little observational data on the subject exists, however.

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space-ModTeam t1_jd21ky0 wrote

Hello u/OysteinM, your submission "Would it work to get 1G in a spacecraft going to Mars using acceleration?" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

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jeffwolfe t1_jd21oog wrote

The surface gravity of Mars is 0.38g. If you're planning to land and stay for any length of time, I wouldn't think you'd need 1g on the way.

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