The Space Flight Thread - Going out-of-bounds irl

[cigint]

If someone doesn’t figure out a way to create artificial gravity (centrifugal force doesn’t work), humans cannot survive interstellar travel.

Why doesn't it work? I thought the primary reason artificial gravity is needed is to not lose muscle and bone mass. It does prevent that.

Likewise, if a way to protect humans against cosmic radiation isn’t discovered (current tech won’t get it done)

We have dense polymers that can absorb the high-energy massive particles and lead shields can dampen photonic GCR. The problem is that shields weigh too much for our launch vehicles. But in this scenario we would be constructing the colony ship in orbit, not launching it from the surface. Of course, since we haven't built anything that large in orbit, it's not correct for me to say we "have" the technology. I mean that this is within our grasp at our current level of technology, unless I haven't taken into consideration something you know about.

 

[Quence]

Why doesn't it work? I thought the primary reason artificial gravity is needed is to not lose muscle and bone mass. It does prevent that.

It’s a curved surface that only kind of works if you walk in one direction. There are all sorts of stability issues for when you turn or reach to the side or even move your head from side to side. And the size of the spinning disk that would he necessary is unworkable for interstellar travel, not to mention the reliability issue for something mechanical and that large.

We have dense polymers that can absorb the high-energy massive particles and lead shields can dampen photonic GCR. The problem is that shields weigh too much for our launch vehicles. But in this scenario we would be constructing the colony ship in orbit, not launching it from the surface. Of course, since we haven't built anything that large in orbit, it's not correct for me to say we "have" the technology. I mean that this is within our grasp at our current level of technology, unless I haven't taken into consideration something you know about.

Tests have shown that various types of shields can absorb some high energy radiation particles, but those particles hit the shield materials and produce new particles that enter the spacecraft and are quite deadly to humans.

Perhaps there’s a way to create a magnetic shield around the ship just as the earth is protected from cosmic rays by a magnetosphere.

 

[Miller]

Scott Manley's review of NASA's Starliner report:

It's a miracle that they managed to reach the ISS.

 

[Wallace]

If someone doesn’t figure out a way to create artificial gravity (centrifugal force doesn’t work), humans cannot survive interstellar travel.

If/when we get fusion engines, you can just accelerate at a constant 1g. When you get to the halfway point of the trip, turn around and decelerate at a constant 1g.

 

[Quence]

If/when we get fusion engines, you can just accelerate at a constant 1g. When you get to the halfway point of the trip, turn around and decelerate at a constant 1g.

That’s forward motion but I don’t see it as a viable replacement for the effects of real gravity.

 

[teriyakiburns]

That’s forward motion but I don’t see it as a viable replacement for the effects of real gravity.

Constant acceleration simulates gravity because what we call gravity is constant acceleration of an object towards the centre of an idealised mass. We stick to the outside of the earth because we're constantly being accelerated towards its centre; the surface of the earth pushes back. Acceleration, or a change in velocity, is measured in terms of "gravities" or G, which is where the term "g-force" comes from; if an object is accelerated in one direction, it experiences a "gravity" effect in the opposite direction. That's why you feel yourself pressed into a the seat of your car when you accelerate. If you had no external reference, you would believe you were lying on your back or that the car had suddenly pointed up into the air. This is the reference frame, one of the basic concepts of relativity.

If you are inside a box with no windows, reducing your reference frame to what you can see and experience inside that box, and feel an apparent gravitational force, you cannot tell if you are being pulled down by a large mass, or if the box is accelerating upwards, because in both cases the effect is the same; you feel a "force" pulling you to the floor of the box. Give the box a window and you will be able to tell which is which, but you'll still feel the same apparent "force". A person standing inside a spaceship accelerating at 1G (that means it's constantly going faster) will experience earth-equivalent gravity until the ship stops accelerating.

 

[Quence]

Constant acceleration simulates gravity because what we call gravity is constant acceleration of an object towards the centre of an idealised mass. We stick to the outside of the earth because we're constantly being accelerated towards its centre; the surface of the earth pushes back. Acceleration, or a change in velocity, is measured in terms of "gravities" or G, which is where the term "g-force" comes from; if an object is accelerated in one direction, it experiences a "gravity" effect in the opposite direction. That's why you feel yourself pressed into a the seat of your car when you accelerate. If you had no external reference, you would believe you were lying on your back or that the car had suddenly pointed up into the air. This is the reference frame, one of the basic concepts of relativity.

If you are inside a box with no windows, reducing your reference frame to what you can see and experience inside that box, and feel an apparent gravitational force, you cannot tell if you are being pulled down by a large mass, or if the box is accelerating upwards, because in both cases the effect is the same; you feel a "force" pulling you to the floor of the box. Give the box a window and you will be able to tell which is which, but you'll still feel the same apparent "force". A person standing inside a spaceship accelerating at 1G (that means it's constantly going faster) will experience earth-equivalent gravity until the ship stops accelerating.

Not exactly. I believe that the more mass an object has, the stronger its gravitational pull. It’s described by Isaac Newton's Universal Law of Gravitation. Also, it’s theorized that mass emits particles called gravitons, which are responsible for gravitational attraction.

 

[Deep Nozzle Throat]

Didn't know there was a space thread. Neat.

The latest and greatest news from within NASA is Jared Isaacman's Standard Block 1 SLS proposal, which intends to conjure up an ICPS replacement (probably out of a Centaur V) and use it on Artemis III through IV. This has singlehandedly pissed everyone off, not least the fact that this decision was made apparently unilaterally (program heads were just finding out about this when the announcement was made on Friday).

There's a few problems here aside from a Congressional appointee acting unilaterally. The biggest of these is the fact that ICPS's successor, EUS, is Congressionally mandated, and multiple times has avoided getting axed through Congressional line-item approval. A stop work is currently in place on production, but the legal framework of doing so is up in the air. Congress will be debating the 2026 re-authorization act this week, so keep an eye on that.

I, personally, have mixed feelings about the idea. Getting more SLS launches brings the cost down, and descoping AIII to a LEO rendezvous is a reasonable buydown of risk, but conjuring up a brand new stage in the span of about 18 months is practically impossible without a tremendous amount of funding. Centaur V can't do it without major modifications. Same idea that got us from DCSS to ICPS, and that took 5 or 6 years. Plus the fact that nobody was consulted in the process, which even if this is fundamentally a good plan is probably going to summon Congressional ire.

Is it a backdoor plot to kill SLS, or the failings of a space cadet NASA admin? Only time will tell.

 

[gildersleeve]

The larger you make the diameter of the object your rotating the less noticeable the effect of spin is when doing artificial gravity from centrifugal forces. I believe the current limit is a mile in diameter if your attempting to make an idealized O'Neil cylinder (with steel) Which may still affect a ball thrown between two people. But not as extreme as you see when you see centrifugal gravity tests on earth where the diameter of the spinning room is only 50ft.

As an aside. I enjoy thinking about interplanetary travel and trade networks. I have always been partial to the idea of cyclers for trade. Essentially a tin can set on an orbit that encounters two objects, say earth and mars on a regular schedule. You only need to expend energy to accelerate to the object. Dock and set goods for trade, then decelerate to return to your station. The reciever does the same when it encounters their solar body. There doesn't need to be a crew on board the cycler. Of course this isn't fast, but that's not the point for the goods on board. You can make enough of them in the same orbit to have monthly to weekly encounters.
There's also the concept of beamrider networks. Having an array of laser satelites either solar, nuclear or future fusion™ to accelerate ships at 1g using solar sails. And then having a similar array at your destination to begin slowing you down at the midpoint of your journey, theoretically if you have enough energy to do constant accel/decel at the closest encounter you would get to Mars within 3-4 days iirc. Its not even nessicary to accelerate the object the entire time either. If it shortens the journey to a month or two that's acceptable. Keep expanding the arrays across solar bodies and you have an effective interplanetary highway system capable of shuttling people and cargo much faster than current chemical propulsion. The upfront investment is immense as it stands though. And the potential of using it as a weapon of course. Depending on where the array is.

On a more realistic bent, we need a robotic mission to survey lunar lava tubes. The geology is incredibly interesting and I view them as potential colonization targets. Better to use a hole already dug for sheilding than digging one yourself.

 

[Quence]

Vger 1 will be in contact with Earth until 2036. It’s traveling at almost 11 miles per second and yet it won’t reach the Oort cloud for many more decades.

The distances that would be involved with interstellar travel are mind-boggling.