Space Things

[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.

[Irace86.2.0]

Originally Posted by Dadhawk

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.

I thought the article would highlight why we are using them for an abort system (good storage and reliable), but why they aren't used for reusable portions of Starship (toxic/risky in mass/high frequency use cases, corrosive for reuse).

I think the key points would be that Starship and all components are suppose to be reusable, right, and they need to be from fuels that are producible on the moon/mars, right (more on that below)? I think if they used hyperbolic components on any part of the mission then those used components would have to be tossed or refurbished (Source).

This NASA article talks about all the negative events that happened with the storage and handling of hypergolic propellants (at that time, old article), which might be a big aspect on the earth, moon and/or mars.
https://ntrs.nasa.gov/api/citations/...0100042352.pdf

Hypergolic rocket propellants have proven to be a highly reliable asset in manned and unmanned spaceflight; however, their maintenance on the ground has proven to be relatively difficult. Do the operational risks from possible human errors or hardware failures causing a catastrophic incident outweigh the usefulness of hypergols even though they have been used for the last 50 years of manned and unmanned spaceflight? One would have to say probably not, since hypergols are so widely used in the space industry currently and are being proposed to be used on many vehicles in the future. Therefore, ground operations on hypergol systems have become increasingly scrutinized for possible unknowns, and rightfully so. The data shown in this report are not an example of why we should not be using hypergolic propellants on spacecraft and launch vehicles, but rather illustrate what we can and should do to mitigate possible unforeseen ground operation and/or design problems.

Seems like when we look at the MDRM series that I could pull many quotes from why they are going with cryo instead of hypergolic fuels, and it seems everything to do with weight/payload and the ability to make them on Mars. It then comes at no surprise that SpaceX switched from the Falcon 9's Merlin RP-1 based engines to the Raptor engine that is a pump-fed LOX/CH4 based engine. There is plenty of information talking about the risks of using cryo, risks of aborting, benefits of different approaches, their goals, and so on. In light of that, using hyergols for anything other than a long-term, stable propellent for emergency aborts seems like a non-starter.

Mars Design Reference Mission 5.0
https://www.nasa.gov/wp-content/uplo...p-2009-566.pdf

The technology that is proposed for the DRA 5.0 Mars descent and ascent propulsion systems uses a pump-fed LOX/CH4 propellant combination. The O2-based propulsion system was chosen not only to improve performance, but also so that ISRU could be used to produce the required ascent O2 at Mars instead of having to carry it from Earth. This is not a new concept, having been thoroughly analyzed in previous Mars Design Reference missions. Currently, no pump-fed LOX/CH4 engines are in production, and only pressure-fed engines are in development. Much research and testing is required to produce a highly reliable, pump-fed engine that could meet the human Mars mission requirements. The LOX/CH4 engines face the challenge of having to start after sitting idle for an extended period of time (in this case, on the martian surface). Pressure-fed engines have been considered to alleviate this concern. Without the rotating turbo machinery, pressure-fed engines are much simpler and more reliable than their pump-fed counterparts. However, while the engine dry mass for the pressure-fed engine is lower than for the pump- fed engine, the overall feed system mass is much higher due to the higher pressure that must be maintained in the propellant tanks (250 psia vs. 50 psia). The required helium pressurant (and tanks) is also greater. This problem is made even worse due to the lower (in general) Isp, and corresponding higher propellant requirement, of the pressure- fed technology. These factors result in much lower payloads that could be delivered. Therefore, pump-fed engines are chosen for CH4 engines in the current mission. Also, the work and testing that is required to verify that the LOX/LH2 engine starts after long idle times would, hopefully, solve any issues with the LOX/CH4 start capability.

It would be nice if a hypergolic propellent could be used as the ignition to get things going, almost like the hydrogen bomb was three bombs in one, or like how the Maserati precombustion chamber works. This way the primary propellant isn't hypergolic, only a small amount is needed in production, handling, storage and damage, yet the risks are lower.

[Ultramaroon]

Originally Posted by Irace86.2.0

We can make a ship modular to make it huge, but this is like stacking more trollies to a train.

I am SO yanking your chain.

[Irace86.2.0]

Originally Posted by ZDan

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

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.

I thought we were done, but okay, I'll bite. Seems like interesting stuff.

I'll concede that his understanding of physics, engineering principles, chemistry has likely improved, and in the beginning, it could have been much worse. It is reasonable to think they would improve over time, wherever they began, but he seems to have a comprehensive knowledge of his products at a deeper level than most CEOs, and I'll stand by that. It is hard to not come away with that conclusion after watching any number of videos of him discussing SpaceX components, as I shared.

Well, he didn't say vacuum tubes; he said low pressure, but technically any significant pressure differential is a vacuum, so a tube with marginally lower pressure than atmospheric could be a vacuum, even if the differential isn't great. What he proposed wouldn't work in a perfect vacuum because he specifically said the design would take "high pressure air on the nose," so how could it be a perfect vacuum and generate high pressure on the nose? I don't know the feasibility of transferring the ram air effect on the nose through some type of electric air compressor (electric supercharger) and pumping it through legs/skis at high pressure to create a low resistance surface. I don't know the feasibility of pumping air out of a tube to match the 0.3 bar of pressure at flying altitudes. Like a home vacuum will do 0.2 bar, so I don't know what electric pumps could do to such a huge space. I don't know if there are any theoretical benefits to using air pressure for levitation versus maglev technology, as it relates to energy expenditure or load limits. I am not an engineer. What's your objection?

The Boring company is likely the big plan for avoiding radiation on Mars by digging tunnels and underground structures. The dose radiation is not fatal though. The risk of cancer just goes up. It is generally agreed that an extra exposure of 1 Sv of radiation per year is associated with a 5% increase risk of cancer later in life, and they are saying that the exposure on mars would be around 0.25 Sv per year (more for the mission because astronauts get higher doses in space), but around 1 Sv in four years for easy math. If this was a linear relationship then 20 Sv would increase someone's risk of cancer by 100% or double their risk. Smoking increases ones risk of lung cancer by 15 to 30 fold, or 1,500% to 3,000%. Low dose of radiation over a longer time is worse than that same accumulative dose over a short time, so it may be hard to extrapolate the risks comparing it to say nuclear radiation exposure in high doses. There are processes in the body to repair tissues and damaged DNA, so exposure of time could up regulate repair mechanisms. We really don't have a definitive answer for the level of risk.

[Irace86.2.0]

@Dadhawk

What I proposed doing (using hyperbolic propellants as an ignitor when I mentioned the H-bomb/Maserati examples) is discussed in detail in this video at 29:08, and apparently SpaceX uses those on its Merlin engines for Falcon 9 and Falcon Heavy, but it doesn't use them on the Raptor engines. Instead, they use torch ignitors on the Raptor 1 engines for the pre burners and main engine, and on the Raptor 2 engines, they only use torch ignitors on the pre burners, which removes components that can fail, but makes startup a little more complicated.

Maybe like Destin says, there will be an option for Astronauts to light a burner from the ground or throw some hypergolic "water" balloons into the engines from the lunar surface I'm hoping we will learn more in the future.

[Irace86.2.0]

[ZDan]

Originally Posted by Irace86.2.0

I'll concede that his understanding of physics, engineering principles, chemistry has likely improved, and in the beginning, it could have been much worse.

? The vid I showed is from a few years ago. Not "in the beginning". Curious words, suggesting Musk-worshippers consider him kind of a diety! I don't. I think he's both an idiot (forgiveable) and a total asshole (not forgiveable).

Well, he didn't say vacuum tubes; he said low pressure

Jeebus effing gawd, specifically why I said "or low pressure".

Bottom line: It's a dumb idea that won't work. "Air bearings" in a vacuum (or "low pressure") tube, I mean it's laughable. Anyone who has any sense knows this. Which is why he reverted to fricking *wheels* to support the vehicle not long after that video. Somebody who wasn't afraid of being fired told him it was a stupid idea and wouldn't work.

Regarding Mars mission, it's a death sentence to anyone who signs up. While I agree with the *idea* of space exploration by humans, the possible benefit has to be weighed against the *cost*. Throwing a few humans to Mars might be a neat thing to do but IMO it is not worth ruining and/or extinguishing their lives, no matter how many people would willingly sign up for it.