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Why haven't we gone back to the moon?

by DruidArmy
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D H
#37
Sep2-14, 08:26 PM
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Quote Quote by vociferous View Post
I did read the entire article.
Did you read the part that said "Nobody knows how to do it"?

That is the key sentence in the entire article.

For instance, I do not interpret the article to imply that he felt it was impossible to use thrusters at all to slow the descent, which would be absurd since the Viking landers used thrusters on Mars.
That's a non sequitur. The Viking landers could use thrusters to land precisely because they were small. One of the myriad of nasty facts that confronts putting humans into space is the square-cube law. If you scaled a mouse up to the size of an elephant it would die. The square-cube law dictates that elephant physiology is very, very different from mouse physiology. The same applies to those little Viking landers. Space vehicles don't scale up because of the square-cube law. More mass needs to be added because of structural integrity issues. More thrusters needed to be added because thrust is proportional to throat area. That means even more mass. The end result is that a large vehicle is elephantine compared to the mouselike characteristics of a small vehicle.

Furthermore, I am not convinced that the turbulence is an insurmountable engineering program.
It is a huge issue, one we do not know how to solve.


We've been landing VTOL craft on Earth using nothing but thrust since before we landed men on the moon.
That's another non sequitur. Aircraft don't carry their own oxidizer, and they don't go anywhere close to the speed of a reentering spacecraft. It's more like 1/20th of the speed in the case of a VTOL aircraft vs a reentering spacecraft, and that means 1/400th the energy needs to be dissipated.


Even if, for the sake of argument, we just agree that it is impossible to land such a single mass on Mars, then we simply use a different engineering paradigm.
It's so simple if you simply hand-wave away all the problems!

There's only so much you can shrink a spacecraft that will safely land humans. The Apollo command modules were 6.5 times as massive as is the Mars Science Laboratory rover. Landing a vehicle that is 6.5 times heavier not just 6.5 times harder. It's harder than we can imagine. We don't know how to do it. The Apollo command modules carried the barest minimum of life support needed to bring humans from separation from the service module down to the Earth, where they would be whisked away via helicopter shortly after splashdown. A Mars lander would need to carry a significant amount of life support (air, water, food, life support equipment, etc.). And a hefty rover. And a launch vehicle.

Why a launch vehicle? Not bringing the astronauts back home is a death sentence. We haven't the foggiest idea of how to grow food away from home. For a little while, and for a few bites of lettuce to augment otherwise boring freeze dried food, yes, we can do that. A fully sustaining farm? We don't know how to do that.

Why a rover? Unless we can land several months worth of life support with that one vehicle, we need to send multiple landing vehicles. Those other landers are likely to land tens of kilometers apart. The Mars Science Laboratory represents the state of the art in precision landing on Mars. It's one sigma landing ellipse was 20 km × 7 km. The probability of landing within that one sigma ellipse is about 39%. Tripling each dimension (60 km × 21 km) yields a probability of 98.9%. Those aren't great odds, but close to the target for human spaceflight activities. We'll need that rover to go pick up the water, food, and equipment that landed tens of kilometers away.

I think the crux of the difference is between understanding the distinction between us not having a fabrication-ready design for a Mars mission today and a Mars mission simply being beyond our current level of technology.
I think the crux of the problem is that you don't know how impossibly hard it is, even using technology that doesn't exist yet. We don't know how to do it. I've mentioned but three of the things we don't know how to do. There are a number more.
phinds
#38
Sep2-14, 08:33 PM
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Quote Quote by vociferous View Post
Fair enough; I am just stating my opinion as you are stating yours .
Well, it does seem that your "opinion" is based on wishful thinking and a very selective reading and interpretation of the information available whereas Drakkith's is based on a pretty straight forward reading of the same information. I don't think anyone here is trying to give you a hard time but it IS frustrating that you don't seem to understand or appreciate the difficulties that have been mentioned to you.
vociferous
#39
Sep2-14, 09:44 PM
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Quote Quote by D H View Post
Did you read the part that said "Nobody knows how to do it"?

That is the key sentence in the entire article.


That's a non sequitur. The Viking landers could use thrusters to land precisely because they were small. One of the myriad of nasty facts that confronts putting humans into space is the square-cube law. If you scaled a mouse up to the size of an elephant it would die. The square-cube law dictates that elephant physiology is very, very different from mouse physiology. The same applies to those little Viking landers. Space vehicles don't scale up because of the square-cube law. More mass needs to be added because of structural integrity issues. More thrusters needed to be added because thrust is proportional to throat area. That means even more mass. The end result is that a large vehicle is elephantine compared to the mouselike characteristics of a small vehicle.


It is a huge issue, one we do not know how to solve.



That's another non sequitur. Aircraft don't carry their own oxidizer, and they don't go anywhere close to the speed of a reentering spacecraft. It's more like 1/20th of the speed in the case of a VTOL aircraft vs a reentering spacecraft, and that means 1/400th the energy needs to be dissipated.



It's so simple if you simply hand-wave away all the problems!

There's only so much you can shrink a spacecraft that will safely land humans. The Apollo command modules were 6.5 times as massive as is the Mars Science Laboratory rover. Landing a vehicle that is 6.5 times heavier not just 6.5 times harder. It's harder than we can imagine. We don't know how to do it. The Apollo command modules carried the barest minimum of life support needed to bring humans from separation from the service module down to the Earth, where they would be whisked away via helicopter shortly after splashdown. A Mars lander would need to carry a significant amount of life support (air, water, food, life support equipment, etc.). And a hefty rover. And a launch vehicle.

Why a launch vehicle? Not bringing the astronauts back home is a death sentence. We haven't the foggiest idea of how to grow food away from home. For a little while, and for a few bites of lettuce to augment otherwise boring freeze dried food, yes, we can do that. A fully sustaining farm? We don't know how to do that.

Why a rover? Unless we can land several months worth of life support with that one vehicle, we need to send multiple landing vehicles. Those other landers are likely to land tens of kilometers apart. The Mars Science Laboratory represents the state of the art in precision landing on Mars. It's one sigma landing ellipse was 20 km × 7 km. The probability of landing within that one sigma ellipse is about 39%. Tripling each dimension (60 km × 21 km) yields a probability of 98.9%. Those aren't great odds, but close to the target for human spaceflight activities. We'll need that rover to go pick up the water, food, and equipment that landed tens of kilometers away.


I think the crux of the problem is that you don't know how impossibly hard it is, even using technology that doesn't exist yet. We don't know how to do it. I've mentioned but three of the things we don't know how to do. There are a number more.
I am not trying to downplay the challenges. However, I believe that the challenge of landing people safely on Mars today is very similar to the challenge of landing people safely on the moon in 1960. We have the basic technological know-how, but it is near the edge (although I would argue that we are at a much better starting position for a Mars mission today than we were for a moon landing in 1960).

The cost of the Apollo program was around $100 billion dollars and it would not be surprising to see a Mars mission cost $1 trillion or more. I'm confident if the budget were there, just like the Apollo program, the results would follow.

The only counterpoint to this is a seven year old article about a decade-old conference that took place around the same time that President Bush committed NASA to a manned Mars mission, before any serious planning about how to effect that had occurred.

By contrast, much more recently, a workshop group of more than 60 individuals representing more than 30 government, industry, academic and other organizations has found that a NASA-led manned mission to Mars is feasible if the space agency's budget is restored to pre-sequestration levels. [1]

I am not an engineer, but I'm pretty confident that our current state of technology is commensurate with engineering such a mission in the next decade or two.

REFERENCES:

[1] http://www.space.com/24268-manned-ma...asibility.html
D H
#40
Sep2-14, 11:40 PM
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Quote Quote by vociferous View Post
I am not trying to downplay the challenges.
That is exactly what you are trying to do.


However, I believe that the challenge of landing people safely on Mars today is very similar to the challenge of landing people safely on the moon in 1960.
Getting to Mars now is much harder than was getting to the Moon then. The breakthroughs needed in the 1960s to land on and return from the Moon were simple compared to those needed to land on and return from Mars.

Another problem is politics and money. The Apollo mission was uniquely situated in history. There was a perceived threat in the US that Russia was getting ahead of the US technologically. Apollo would never have happened without that perceived threat, or without the perpetual duck and cover exercises (youtube video: https://www.youtube.com/watch?v=IKqXu-5jw60) throughout the 1950s and into the early 1960s. The US was very afraid of what Russia might do (and Russia was very afraid of what the US might do). It was a time of MADness.


By contrast, much more recently, a workshop group of more than 60 individuals representing more than 30 government, industry, academic and other organizations has found that a NASA-led manned mission to Mars is feasible if the space agency's budget is restored to pre-sequestration levels. [1]
Did you read your cited article? It targets a "manned mission to Mars By 2030s" -- in other words, 25 years from now. That is perhaps doable with pre-sequestration funding levels, with some international participation to augment that pre-sequestration level funding. It does not require Apollo-style funding. Apollo-style funding is a pipe dream. That kind of funding will not happen until another major perceived threat appears.

Let's say we do start a long term project to send people to land on and return from Mars. Rhetorical question: What happens after that? The answer is to learn from history. What happens after that is what happened to NASA after they landed a few men on the Moon. What politicians from both sides thought was "Mission accomplished, and now we better clamp down on NASA before they bleed us dry." The end result: NASA went through a rather bleak period from the early 1970s to the late 1980s where they received far less money in inflation-adjusted dollars than they receive now, post-sequestration.

I predict the exact same outcome should NASA focus on sending humans to Mars. We might accomplish that mission, but it will be followed by decades of stagnation. IMHO, a much better objective is for NASA to find a way to show that space is profitable. The asteroid recovery plans are the best thing NASA has come up with for a long time. Show that space is a profit center rather than a cost center and we'll have people in space for a long time to come. Some of them will be doing science, a good deal more science than the meager amount done now. Humanity will be stuck here on Earth with little dribbles of funding for space exploration every now and then if space exploration turns out to be not at all profitable.


I am not an engineer, but I'm pretty confident that our current state of technology is commensurate with engineering such a mission in the next decade or two.
I am an engineer. In fact, I am an aerospace engineer who works with NASA, and I'm pretty confident that this is not the case.
Chronos
#41
Sep3-14, 12:36 AM
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Even with our modern engineering savvy, manned space missions are obscenely expensive. The He3 carrot still dangles in front of us, but, who is willing to gamble vast resources without proven technology to utilize it?
phinds
#42
Sep3-14, 05:43 AM
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Quote Quote by vociferous View Post
I am not trying to downplay the challenges.
I can believe that you BELIEVE you are not but you have made it abundantly clear that you simply don't understand them and you in fact ARE downplaying them to a ridiculous degree.
enorbet
#43
Sep4-14, 10:49 AM
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I am of the considered opinion that it will not only not be mere decades but actually Lifetimes before we land humans on Mars, absent some (and not just a few) fairly extreme technological breakthroughs, not the least of which is propulsion and radiation shielding. I utterly hate concluding this, but "if wishes were horses....".

It seems to me that in a fairly short time, perhaps that decade or two, we could have a Moon Base IF we had the will, which we apparently don't. It is my understanding that despite the apparent fact that such mass conflicts as WWII are a thing of the past, and a more Guerilla/Covert type of conflicts are more likely, the US spends more in a day on Conventional Defense (even though there is no single perceived enemy as during the Cold War) than NASA receives in an entire year.

It is also my understanding that during the height of the Apollo Mission the expenditures reached more than 1% of the National Budget, still a mere fraction of the Defense Budget at that time and even less now.

Quote Quote by Wikipedia_Apollo_Project
In 2009, NASA held a symposium on project costs which presented an estimate of the Apollo program costs in 2005 dollars as roughly $170 billion. This included all research and development costs; the procurement of 15 Saturn V rockets, 16 Command/Service Modules, 12 Lunar Modules, plus program support and management costs; construction expenses for facilities and their upgrading, and costs for flight operations. This was based on a Congressional Budget Office report, A Budgetary Analysis of NASA’s New Vision for Space, September 2004.[71] The Space Review estimated in 2010 the cost of Apollo from 1959 to 1973 as $20.4 billion, or $109 billion in 2010 dollars, averaged over the six landings as $18 billion each
Very few people understand the payoff, considering all the advances in so many areas, of those expenditures. Even such mundane things as textiles and fasteners (affecting many kinds or work wear and hazard wear as well as specialized medical condition protective attire, just to name a few) let alone the huge effect on micro-electronics, without which we would not be having this conversation not to mention a complete shift in economic base to Information.... none of this and much more would have occurred.

However for the average businessman, politician, man-on-the-street this is all too abstract (read as "nebulous pie-in-the-sky") to actually divert expenditures from the closer to home, sexy new bomber (who cares if they rust away in some hangar? ...just in case, right?)

Many, even those "in the business" thought JFK's challenge was impossible to achieve at even twice the timeframe, but somehow a flame was ignited AND FUNDED and the rest is now History. I think it foolish to dismiss this as "just lucky" and impossible to reproduce.

Maybe it would take 20 years instead of 10. That is uncertain. What is certain is that we will never do it unless we begin to take it seriously and make it common knowledge just how beneficial Apollo really was on a global scale to an inestimable number of people, some of whom are alive today because of it.
Damo ET
#44
Sep5-14, 06:18 PM
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Quote Quote by enorbet View Post
Very few people understand the payoff, considering all the advances in so many areas, of those expenditures. Even such mundane things as textiles and fasteners (affecting many kinds or work wear and hazard wear as well as specialized medical condition protective attire, just to name a few) let alone the huge effect on micro-electronics, without which we would not be having this conversation not to mention a complete shift in economic base to Information.... none of this and much more would have occurred.

However for the average businessman, politician, man-on-the-street this is all too abstract (read as "nebulous pie-in-the-sky") to actually divert expenditures from the closer to home, sexy new bomber (who cares if they rust away in some hangar? ...just in case, right?)
Maybe it would take 20 years instead of 10. That is uncertain. What is certain is that we will never do it unless we begin to take it seriously and make it common knowledge just how beneficial Apollo really was on a global scale to an inestimable number of people, some of whom are alive today because of it.

Enorbit, they are words plucked straight from my thoughts!
I believe that this is the fundamental problem that the western world faces, and unfortunately no amount of education, reasoning or even scare tactics will convince the 95% of the population (which enjoy western freedoms) that spending in science of ANY disipline is worth the payoff. Give them the internet with every educational book ever written, every science theory ever postulated, every forum like this, and what do they do, search for boobs!

"I stupid people, they are everywhere, they don't even know they are STUPID!"


Damo
Drakkith
#45
Sep5-14, 06:29 PM
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Just because someone doesn't know much about science and technology, or has different priorities than you, does not make them stupid. Most people are not stupid.
enorbet
#46
Sep7-14, 05:50 PM
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Given the technological difficulties as well as the socio-political environment, I am betting..... let's say $10,000 that I will not only be dead but long dead before another single human sets foot on the Moon, forget about Mars. If I'm wrong and you wish to collect I will instruct my lawyer to place the 10K on my headstone in a ziploc baggie (he assures me he is trustworthy). If you think my estimate too long and think you can win this bet and this bet interests you, I also deal in bridges. :P
Damo ET
#47
Sep8-14, 06:37 AM
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Fair point Drakkith, that was a very generalized statement.

It is just so frustrating that our society values such trivial things/people over the genuine contributors to the advancement of our species in becoming more than just consumers and another transient lifeform on this planet.
What happened to the days when 'our' celebrities were people like Einstein?


Damo
phinds
#48
Sep8-14, 07:42 AM
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Quote Quote by enorbet View Post
Given the technological difficulties as well as the socio-political environment, I am betting..... let's say $10,000 that I will not only be dead but long dead before another single human sets foot on the Moon, forget about Mars. If I'm wrong and you wish to collect I will instruct my lawyer to place the 10K on my headstone in a ziploc baggie (he assures me he is trustworthy). If you think my estimate too long and think you can win this bet and this bet interests you, I also deal in bridges. :P
D H
#49
Sep8-14, 08:25 AM
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Quote Quote by enorbet View Post
Given the technological difficulties as well as the socio-political environment, I am betting..... let's say $10,000 that I will not only be dead but long dead before another single human sets foot on the Moon, forget about Mars.
That's a fair bet if you are seventy years old. If you are sixty or less, it's not such a good bet.

NASA is working on plans to send humans to Mars in the 2030s (e.g., 2039 counts, so about 25 years from now) and do so within the constraints of a pre-sequestration budget with only small, inflation-level increases over the course of that 25 years. That 25 year period gives more than enough time to develop solutions to the hard engineering problems outlined earlier in this thread, and it gives time to do so incrementally.

Funding at a pre-sequestration budget level means a bit more than half a percent of the federal budget. That's tiny compared to the unsustainable Apollo-level funding which peaked at 4.4% of the federal budget. This pre-sequestration level funding is arguably sustainable for the long term. An Apollo-style program is not, but this is not an Apollo-style program.
phinds
#50
Sep8-14, 09:46 AM
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Quote Quote by D H View Post
NASA is working on plans ...
Have you ever really looked at the outcome vs the plans for ANY major NASA mission? I point you specifically to the costs and timelines for both the Space Shuttle and the International Space Station. The plans are a joke compared to what really happens.
Domenico94
#51
Sep8-14, 10:10 AM
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Because we have not only the moon....there are many other planets to explore...like mars, for example, and so on..
Drakkith
#52
Sep8-14, 10:17 AM
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Quote Quote by Damo ET View Post
What happened to the days when 'our' celebrities were people like Einstein?
Remember that back in those days we didn't have movies, TV, radio, the internet, and other ways of getting information out. The only people who became famous were those who did something that made the newspapers, such as scientists, politicians, and sports stars.


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