Space Things

[Irace86.2.0]

Originally Posted by bcj

We're coping with this 24/7 right here in this gravity sink. WTF?
There's fuel available without dinking around with the moon or Marz.

Is English a second language for you? I ask because you seem to speak in unintelligible ways. That's not a dig. I'm just curious because your sentences are incomplete and indirect. We're coping with what? This what? With gravity? With fuel payload constraints?

Yes, we have plenty of fuel here, but we need it up there, so we can go to Mars and back easier. The Starship is 90% fuel with 4600 T of propellant, but only has a payload of 100-250 T depending on whether the rocket will be reused or not. That is because, as you put it, we live in this [large] gravity sink, and most of that propellant is used to escape earth's gravity. The energy needed to escape the moon's gravity is far less, so suddenly that payload gets much larger, or refueling Starship means there is a lot of unspent fuel that can be used on a mission to mars.

Let's put it this way: Say you want to drive around the equator at 25,000 miles, but you couldn't refuel; at 25 mpg, that is about 1000 gallons or having a fuel tank that weighs 8,000 pounds; probably need a bigger vehicle, and now it probably doesn't get 25 mpg; wouldn't it be easier to refuel along the way instead?

Option A) we can build an even bigger rocket than Starship to have enough fuel to escape earth's gravity, that can accelerate in space to mars, can decelerate to land on mars and then launch to escape Mar's velocity and have enough fuel to accelerate to earth and decelerate to land, but we must remember that 90% of the rocket is already propellant, so how big would this rocket be?

Option B) we can launch a bunch of payloads of fuel to orbit, launch a final large rocket to space and refuel before going to mars and back.

Option C) we can launch less payloads of fuel to orbit, launch a final rocket into space that doesn't need to be as big, refuel before going to mars, and then refuel on mars before heading back to earth.

Option D) we could refuel in space, go to the moon, refuel before going to mars, refuel on mars then head back to the moon and go back to earth.

Say we could do Option D): would we have enough fuel to reach higher velocities, so we could cut the time to mars shorter? Probably. It is the best chance to get there faster, if the procession of the planets allow a faster route, but going back to what I was saying before, we don't have a ship large enough that holds enough fuel such that we could flat out accelerate half the distance to mars and decelerate the second half of the distance. Our best scenario is refueling on the moon or in orbit around the moon, so Starship is full when it leaves the moons gravity, and then it will burn the rockets to about 50% fuel (minus burnoff), and then it will coast for weeks to months before igniting the burners to slow the rocket before landing on Mars, where it will then refuel, launch into space with refueling payloads, return to refuel, and then leave from space refueled.

Is refueling in space and the back and forth costing more time than saving time with a slower straight shot? Probably not. Average velocity would go up and trip time would decrease going faster. This is like doing a cannonball run from NY to LA and saying, 'wouldn't it be better traveling 65 mph and stopping less to refuel because you get better gas mileage than traveling at 110 mph and needing to refuel more often?" For a trip from NY to LA, that speed differential is a difference of saving 12 hours, but the refueling time is not 12 hours, so the extra few stops is entirely worth it.

[Irace86.2.0]

Originally Posted by Dadhawk

Actually if you could accelerate the ship at 1g or less constantly it would feel like Earth and potentially provide "artificial" gravity wouldn't it?

At an acceleration of 1G you can reach the speed of light (in theory) in about one year with minimal effect.

When there is no acceleration (you are coasting) you are experiencing zero g which is just about as bad to me.

Yeah, 1G would be ideal, for sure. Maximum g's in a rocket is around 3g. Less ideal. Angular acceleration is a better mechanism for inducing gravity.

Obviously we can't reach the speed of light, but I get what you mean.

My point isn't a practical one; it was more of a theoretical one that the fastest a rocket with unlimited potential to accelerate would necessarily have to spend half its time decelerating too. Such a hypothetical "fastest trip" would be miserable, accelerating at levels of G that would crush a human. As you pointed out, even at 1G the ship would accelerate to the speed of light in a year. As it stands, we don't have the ship size with enough thrust power and energy to go at or beyond G for very long, so this isn't an issue. We are talking second/minutes, not hours or days or weeks. At best we can hope to reach a faster coasting velocity that could shorten the trip considerably, but I don't know the math on what we could do with rockets at the thrust and scale of the ones we have with the need to decelerate and land at the end of a long trip when we have burnoff too.

Where is Bob Lazar with a gravity machine?

[NoHaveMSG]

Originally Posted by Irace86.2.0

Is English a second language for you? I ask because you seem to speak in unintelligible ways. That's not a dig. I'm just curious because your sentences are incomplete and indirect. We're coping with what? This what? With gravity? With fuel payload constraints?

You are too literal. Not everyone speaks directly, accounting for every qualifier a statement may infer the way you do. We have had misunderstandings in the past due to this.

As Dadhawk already said, I always thought the idea behind the 1g acceleration/deceleration was for gravity simulation

[Dadhawk]

Originally Posted by Irace86.2.0

They have their reasons. There is a lot of good reasons discussed here:

https://everydayastronaut.com/abort-towers/

This is talking about using liquid fueled and "built in" escape rockets instead of the solid fuel rocket towers used previously. there was some discussion of hypergolic engines but it was mostly positive other than the fuels are toxic to handle.

The situation I'm talking about is not the emergency situation but the ascent from the Moon. Maybe Starship's size is what requires more standard liquid fuels, but it does introduce an ignition risk.

[Irace86.2.0]

Originally Posted by NoHaveMSG

You are too literal. Not everyone speaks directly, accounting for every qualifier a statement may infer the way you do. We have had misunderstandings in the past due to this.

As Dadhawk already said, I always thought the idea behind the 1g acceleration/deceleration was for gravity simulation

In a practical sense, it can't be done linearly. It can only be done with angular acceleration.

[NoHaveMSG]

Originally Posted by Irace86.2.0

In a practical sense, it can't be done linearly. It can only be done with angular acceleration.

I wasn't talking about practicality, I just explained my understanding of what I thought the primary reason for the accel/decel idea behind long distance space travel was. There are quite a few obstacles to it, I thought it was neat as opposed to just rotating the craft.

[bcj]

Originally Posted by Irace86.2.0

Is English a second language for you? I ask because you seem to speak in unintelligible ways. That's not a dig. I'm just curious because your sentences are incomplete and indirect. We're coping with what? This what? With gravity? With fuel payload constraints?

Replying succinctly to your assertion that humans are unable to cope adequately with sustained acceleration.
What's so hard to comprehend?

Why concentrate solely on planetary destinations when planning the entire world wide space exploration agenda? Too limited.

I propose that more good will accrue by spending at least a fraction of the attention on manufacturing stuff (42 [HHGTTG]) in space.
Working out how to set up solar powered fractional distillation from random things already outside planetary reference frames would be preferable in my estimation.

[Irace86.2.0]

Originally Posted by NoHaveMSG

I wasn't talking about practicality, I just explained my understanding of what I thought the primary reason for the accel/decel idea behind long distance space travel was. There are quite a few obstacles to it, I thought it was neat as opposed to just rotating the craft.

Yeah, as a hypothetical, it would be good, but it also would negate some of my points on the fastest hypothetical trip possible, which would be accelerating to max G for 50% only to decelerate to max for 50%. I wouldn't want to weigh 450+ pounds for weeks to months. If they could do a G for the entire distance then that would be great, hypothetically, of course.

[Ultramaroon]

Originally Posted by Irace86.2.0

In a practical sense, it can't be done linearly. It can only be done with angular acceleration.

With enough fuel, anything is possible.

[Ultramaroon]

Originally Posted by bcj

Replying succinctly to your assertion that humans are unable to cope adequately with sustained acceleration.
What's so hard to comprehend?

He don't know you like I knows you.

[Irace86.2.0]

Originally Posted by bcj

Replying succinctly to your assertion that humans are unable to cope adequately with sustained acceleration.
What's so hard to comprehend?

Why concentrate solely on planetary destinations when planning the entire world wide space exploration agenda? Too limited.

I propose that more good will accrue by spending at least a fraction of the attention on manufacturing stuff (42 [HHGTTG]) in space.
Working out how to set up solar powered fractional distillation from random things already outside planetary reference frames would be preferable in my estimation.

Again, your first sentence is an incomplete sentence. I'm not trying to be the grammar police. It just gets confusing trying to determine what you are referencing in an incomplete sentence. You know in your mind, but it is confusing on the other end from my perspective.

I reread your former posts, and I get now what you were referencing, and I get your confusion or reason for your response. I distinctly said G's and not a G. Experiencing G's of acceleration, even two or more G's would instantly double your weight like going from 150lbs to 300lbs. Max G on a rocket is around 3G's, but in my hypothetical "fastest reasonable trip", maybe we would do more. Feeling higher levels of G's would be problematic, and then fatal, and then higher still, would leave our bodies putty like a jellyfish out of water.

On your second point, I don't know if this was directed at me and something I said, or if it is a general talking point you just wanted to mention because you don't seem to be referencing something I said directly or your last quote that I was responding to in an effort to now clarify your prior statements, but to respond, I don't think anyone is ONLY trying to go to other planetary bodies, and I don't know that any one company or government is planning "the entire world wide space exploration agenda," so I'm confused by that statement. You even post a link and address the fact that there are other space projects in the works.

The current plans by NASA using US space contractors are intentionally designed to do more than just get us to the moon and back. They are designed to be cheaper, faster and capable of more than a single purpose. This is like building a more complex and expensive building like a hospital (I'm a nurse, so I'm using a personal reference) that is future proof because it is modular and can be expanded upon; it doesn't have to be torn down and rebuilt from scratch when they need to expand its capabilities or size. Similarly, this will be an architecture that is necessary to save money and time, and it will allow NASA and partners to reach Mars and beyond in far more feasible ways under a smaller budget. If someone figures out a better means then I'm sure a company or government will do that.

[Spuds]

Actually 1g (or that of whatever planet you are going to) flat rate burn mixed with periods of higher g burns is a better architecture for deep space human exploration than single long burn up front and at the end. It takes longer, but you can always plan to resupply mid journey with high speed cargo flights. Cargo doesn't really care what acceleration you are pulling for long periods of time.

Anything is possible, nothing is easy.

[Irace86.2.0]

Originally Posted by Ultramaroon

With enough fuel, anything is possible.

We can make a ship modular to make it huge, but this is like stacking more trollies to a train. As you do that, the force needed to reach 1G of thrust is higher (F=ma). Okay, so you get bigger engines, but they also require more fuel, so you add more trollies.

A Bugatti will pull over 1G at times trying to get to 200mph. At its top speed fighting gravity it is barely accelerating, but if it didn't have air resistance or rolling resistance then it would be continuing to accelerate, and it would deplete its fuel in twelve minutes operating its engines at peak levels. Rockets deplete their engines in minutes, and they are 90% fuel. How large of rocket would you need, and how large of a rocket engine/s would you need to create the thrust to move that gargantuan mass at 1G through space? If it is even theoretically possible, it would surely be unrealistic for humans to produce using propellant based propulsion.

[ZDan]

Originally Posted by Irace86.2.0

I said he clearly is knowledgable about the specifics beyond what your typical CEO would know.

He has information on a few subjects, but his working knowledge is largely crap.

What those videos I posted, and he doesn't sound like Billy Madison, which is who you paint him out to be.

I don't know who Billy Madison is. But check *this* video. Another idea that actually isn't his own (vacuum train idea has been around for ~100 years) that he presents as his novel, ingenius, EASY idea for transportation: Trains in elongated vacuum tubes for hundreds of miles (not practical already), that ride on *air bearings*. IN A VACUUM (or low pressure) TUBE. He knows enough to spew b.s. but in fact his ideas on how things work in the real world is abysmal.

Also, colonizing mars is an idiotic idea with 21st century tech. But he wants it so bad he just dismisses some of the major health concerns and says "radiation isn't that big a deal".

He's smart enough to make non-science non-engineers *think* he's smart. But he does not have any kind of grasp on science or engineering.