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Old 13th October 2017, 09:23 AM   #281
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Originally Posted by Roboramma View Post
Well, in that case we do have to consider the issue of getting those people back to earth.

On the other hand, if we want to ignore that issue then we do have to consider the other issues related to colonization. We can't have it both ways.
Just building a cheap transportation link is a major leap forward. Selling the service to NASA to send large robots and bring back large samples would greatly advance humanity's scientific knowledge all by itself. Congress would probably be able to find room in the budget for something like that.
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Old 13th October 2017, 09:29 AM   #282
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Originally Posted by 3point14 View Post
Or until big rocks fall from the sky, we knacker the ecosystem or Donald gets bored and presses the button.
Any of those would still leave Earth in a far better position to support humanity than Mars.
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Old 13th October 2017, 09:47 AM   #283
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Originally Posted by theprestige View Post
Any of those would still leave Earth in a far better position to support humanity than Mars.
Well, no.

A big enough rock falling from the sky is an end event.

As is buggering up the eco system to the point where it simply cannot support life
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Old 13th October 2017, 10:09 AM   #284
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Originally Posted by 3point14 View Post
Well, no.

A big enough rock falling from the sky is an end event.
Is it? The 'dinosaur event' screwed the dinosaurs, but our ancestors survived, together with plenty of other animals and plants. But you did say "big enough", so yeah. Then Mars is just as vulnerable.

Originally Posted by 3point14 View Post
As is buggering up the eco system to the point where it simply cannot support life
Mars cannot support life. If it comes to a choice Earth will always be a better bet for "making do with what's left".
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Old 13th October 2017, 10:11 AM   #285
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Originally Posted by GlennB View Post
Is it? The 'dinosaur event' screwed the dinosaurs, but our ancestors survived, together with plenty of other animals and plants. But you did say "big enough", so yeah. Then Mars is just as vulnerable.
Plenty of dinosaurs survived as well. There are a lot of them today. So that big rock didn't even manage to off them either.
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Old 13th October 2017, 10:15 AM   #286
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Originally Posted by GlennB View Post
Is it? The 'dinosaur event' screwed the dinosaurs, but our ancestors survived, together with plenty of other animals and plants. But you did say "big enough", so yeah. Then Mars is just as vulnerable.

Not to the same rock.


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Mars cannot support life. If it comes to a choice Earth will always be a better bet for "making do with what's left".
Again, not with a large enough rock.

Yes, I realise it's unlikely.
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Old 13th October 2017, 10:18 AM   #287
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Originally Posted by 3point14 View Post
Well, no.

A big enough rock falling from the sky is an end event.

As is buggering up the eco system to the point where it simply cannot support life
Restoring Earth's ecosystem--and surviving in the mean time--would still be easier than standing up an equivalent ecosystem--and surviving in the mean time--on Mars.

Investing in safeguards on Earth to recover from a big enough rock would still be cheaper and easier than investing in establishing a self-sufficient human civilization on Mars.

ETA: And of course a humanity that somehow manages to bugger its entire ecosystem, to the point where Earth is unrecoverably less habitable than Mars, is a humanity incapable
of building an equivalent ecosystem on Mars, or maintaining it to the necessary degree.

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Old 13th October 2017, 10:23 AM   #288
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Originally Posted by theprestige View Post
Restoring Earth's ecosystem--and surviving in the mean time--would still be easier than standing up an equivalent ecosystem--and surviving in the mean time--on Mars.
You seem to be underestimating the size of the rock I am imagining.




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Investing in safeguards on Earth to recover from a big enough rock would still be cheaper and easier than investing in establishing a self-sufficient human civilization on Mars.
I can't disagree with this. I'd be bang alongside some sort of Spaceguard
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Old 13th October 2017, 10:28 AM   #289
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Originally Posted by 3point14 View Post
You seem to be underestimating the size of the rock I am imagining.
How about you come out and say it rather than tease us with your big rock?

Yes, there are risks to being only on Earth, but any rock big enough to crack the planet open we'll spot quite a while in advance. Proper countermeasures could be one of the ways we ensure our survival.

I'm all in favour of colonising other planets, for that reason and others, but it won't be a walk in the park. It would be a lot easier for the whole community to be wiped out on a planet with no breathable air.
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Old 13th October 2017, 10:34 AM   #290
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Originally Posted by Argumemnon View Post
How about you come out and say it rather than tease us with your big rock?
I don't know that I'm teasing. I did say, "A big enough rock falling from the sky is an end event."

Something similar to whatever it may have ben that knocked Mars out of whack or turned the hypothetical fifth rocky planet into the asteroid belt.


Quote:
Yes, there are risks to being only on Earth, but any rock big enough to crack the planet open we'll spot quite a while in advance. Proper countermeasures could be one of the ways we ensure our survival.
I wouldn't bet on that. I also wouldn't bet on being able to do anything about it absent the availability of routine spaceflight, ironically.



Quote:
I'm all in favour of colonising other planets, for that reason and others, but it won't be a walk in the park. It would be a lot easier for the whole community to be wiped out on a planet with no breathable air.
Yes, but the same big rock is not going to hit both planets.
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Old 13th October 2017, 11:17 AM   #291
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Originally Posted by smartcooky View Post
His 20% is like 200% 25% from most others.
That's closer.

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I remember the promises NASA made back in the early 1970's. The Space Shuttle was going to be like this...
Right, but at that time they didn't have experience with enormous solid rocket boosters. As far as I know, they are still the largest ever used. They produced 2.8 million lbs of thrust compared to 1.5 million on Ariane 5. Solid rockets were cheap on Little Joe and Little Joe II. They also seem to work quite well on Atlas V. I have doubts that any solid rocket booster of that size is practical. When you move a liquid fueled rocket you only have the weight of the empty tanks. You can fill them up at the launch pad. But, solid rockets have the full weight all the time.

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... a space plane with a flight-line maintenance type turnaround, launching every week, with re-usability that was going to make putting payloads into orbit cheap.
I think a lot of that had to do with the mass versus re-entry drag. The orbiters were heavy. In contrast SpaceShip One didn't even use a heatshield because of its low mass. We'll have to see if Sierra Nevada can make the concept work with their smaller, lighter shuttle.

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It ran way over budget, cost over $450m per launch (more than twice the cost of any other comparable launch system)
That's not true. The Titan IV cost $637 million per launch and this wasn't improved until it was replaced with Delta IV Heavy at $475 million in 2004.

Both the Shuttle and Titan IV systems cost more per pound to LEO than the Saturn V which was about half that. On the other hand, they were less than the $834 million cost of a Saturn IB. But this isn't a fair comparison. The Saturns and Titan IV's were in short production runs. The cost of Atlas V has been cut more than in half but over a period of 15 years of continuous production.

Quote:
and by having to satisfy the needs of the military (e.g. the payload bay design was changed so that it could launch the NRO's KH-9 Spy Satellite).
This is partly true but it wasn't specifically for the KH-9 which launched in 1971 and was always carried by Titan III's. The Air Force requirement was for an 18 meter length. The KH-9 was just over 16 meters. The Air Force did want 66,000 lbs to LEO even though the KH-9 only weighed about half that. The payload bay width of 4.5 meters was a NASA requirement. Actually, the initial NASA design in July, 1970 only called for 25,000 lbs. And then:
April, 1971: James C. Fletcher was sworn in as NASA Administrator at a White House ceremony. Fletcher decided to push for Congressional approval of the stalled space shuttle program, but found that would only be forthcoming if the US Air Force agreed to participate. In order for that to happen, NASA would have to incorporate the USAF requirements for the shuttle that it had so far ignored (greater payload, higher cross-range).

Here's where the big problem starts:
Nixon's Office of Management of the Budget (OMB) told NASA to expect no budget increases in the next five years (e.g. $ 3.2 billion per year, meaning no more than $1 billion per year could be spent on the shuttle).
And here's the result in November, 1971:
  • The Saturn S-IC flyback booster would use expendable engines, considered a drawback.
  • The new-design pressure fed liquid propellant booster would cost $4.2 billion to develop, plus a recurring cost of $275/kg to orbit.
  • Solid boosters would stage at 5800 kph. A solid booster shuttle would have a 2,221,000 gross lift-off weight equipped with 2 x 156 inch diameter solid rocket motors, loaded with 1.25 million kg of propellant and having a 130 second burn time. Lift-off thrust would be 1,332,000 kgf. Development cost would be $ 3.7 billion, and recurring shuttle cost to orbit would be $500/kg.

In an effort to save $500 million on development costs, NASA nearly doubled the to orbit recurring cost. Also, they originally wanted a two-stage design but settled on a 1 1/2 stage design because of budget constraints.

But, I need to mention something here. The design of the Space Shuttle Main Engines was beyond engineering ability in 1971. They had to invent computational fluid dynamics.

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SpaceX have actually done what they promised They have used reusability to deliver frequent and reliable, low cost payloads to orbit.
I assume you mean that he will do that; he hasn't done it yet. To his credit, his Dragon resupply craft is the only one since the Space Shuttle that can return payload.

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They aren't subject to the biannual and quadrennial whims of politicians
Actually they are. As I've already mentioned, SpaceX exists because of NASA contracts, not because Musk funded everything himself. What he funded was Falcon 1 which boosted 400 lbs into LEO.

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So far this year, they have had fifteen launches, all with 100% successful payload deployments, twelve of which they have successfully recovered the Stage 1 booster
Again, the stated goal is 10 reuses for each engine. We'll see.

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I grow tired of the haters and the TPS merchants people pointing out facts that don't fit my starry-eyed love affair of Elon Musk, I just don't get what motivates people to be so negative about someone who is clearly a visionary when he isn't being delusional and sometimes has the ability to see his ideas through and bring them to fruition.
As I've mentioned, his HyperLoop concept is pure baloney; it will never work. His car is okay, nothing revolutionary about it. I give him credit for reducing the cost to LEO and probably the cost to GEO. And credit for a resupply craft that can return payload. We're still waiting for the Falcon Heavy which will be a milestone at half the weight of a Saturn V. I'm hoping he'll be able to deliver the Dragon II. And, I'm hoping that his vehicles stop blowing up on the launchpad. His self-driving car remains a joke with lots of hype.

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I can only think that envy plays a key part.
I guess you can think that if you want. I've never had any desire to design electric cars or rockets and still have no desire to do a TEDx speech. I suppose I'll have to write a response to the Future of Life paper someday, but of course, Musk is only one signature and he personally knows less than nothing about AI.
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Old 13th October 2017, 11:18 AM   #292
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Originally Posted by 3point14 View Post
Not to the same rock.
True, as I acknowledged.

But a self-sufficient Mars colony (if it's even theoretically possible) will cost many $trillions to set up.

Today I read that the UK health secretary is seriously thinking of banning "walk-ins" to hospital accident+emergency units, to cut costs. You'd have to get verification from your doctor or similar. Arm broken with bone sticking out? Ooooh ... got a note? No? I jest somewhat, but not very much looking at the ways a fairly important economy has sought to save on spending.

Seriously. Nobody will agree to pay for the Mars "backup", especially given that it's far more fragile and vulnerable than what we have down here.
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Old 13th October 2017, 11:32 AM   #293
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Originally Posted by barehl View Post
I think a lot of that had to do with the mass versus re-entry drag. The orbiters were heavy. In contrast SpaceShip One didn't even use a heatshield because of its low mass.
SpaceShipOne doesn't go anywhere near orbit. It reenters at very low speed compared to the shuttle.
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Old 13th October 2017, 11:35 AM   #294
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Originally Posted by 3point14 View Post
I don't know that I'm teasing. I did say, "A big enough rock falling from the sky is an end event."
You keep saying that people don't know what size of rock you refer to. That's entirely on you if you keep that size to yourself.

Quote:
Something similar to whatever it may have ben that knocked Mars out of whack or turned the hypothetical fifth rocky planet into the asteroid belt.
I don't think there's enough mass for a planet in the belt. Ceres by far has the majority of its mass but it's too light to clear its neighborhood.

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I wouldn't bet on that.
Just like I wouldn't bet on the near-future feasibility of interplanetary travel. But we know we can divert asteroids.

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Yes, but the same big rock is not going to hit both planets.
Of course (barring some freak event!) but my point is that it's a lot easier for _any_ catastrophe to wipe out the entire martian colony. You can't run outside and survive on the planet's ecosystem.
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Old 13th October 2017, 11:41 AM   #295
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Originally Posted by Argumemnon View Post
You keep saying that people don't know what size of rock you refer to. That's entirely on you if you keep that size to yourself.
I really didn't think I was being obtuse. A rock big enough to end all life on earth. An end event. Seriously, I'm not trying to be obtuse but to be any more specific I'd have to start sounding patronising. Like now. And I don't want to do that.



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I don't think there's enough mass for a planet in the belt. Ceres by far has the majority of its mass but it's too light to clear its neighborhood.
I think it's an old, discredited theory.


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Just like I wouldn't bet on the near-future feasibility of interplanetary travel. But we know we can divert asteroids.

I would still be very skeptical that such a rock could be detected and moved in time.


Quote:
Of course (barring some freak event!) but my point is that it's a lot easier for _any_ catastrophe to wipe out the entire martian colony. You can't run outside and survive on the planet's ecosystem.
Yes, but it's also almost impossible for one event to wipe out both all life on earth and at the same time destroy any hypothetical Martian colony. That's the point, that's why it's described as 'insurance'.
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Old 13th October 2017, 11:47 AM   #296
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Originally Posted by 3point14 View Post
Yes, but it's also almost impossible for one event to wipe out both all life on earth and at the same time destroy any hypothetical Martian colony. That's the point, that's why it's described as 'insurance'.
Oh, absolutely, and it's a major reason to build colonies ASAP. I'm a big proponent of colonising space (and I don't worry too much about us "contaminating" dead rocks). I'm just worried that it might remain science fiction for the forseeable future. I'll be ecstatic if proven wrong.
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Old 13th October 2017, 11:53 AM   #297
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Originally Posted by 3point14 View Post
Yes, but it's also almost impossible for one event to wipe out both all life on earth and at the same time destroy any hypothetical Martian colony. That's the point, that's why it's described as 'insurance'.
One event? I totally agree with what you say.

But the 'insurance' colony is much more likely to be wiped out by an event before it proves to be of any use in that respect. And it will be more affected by minor attrition, what with having virtually no atmosphere.

For insurance against hurricanes, do you:

a) Build a hurricane shelter near your house
or
b) Build a second house in the worst slum in Bogota?
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Old 13th October 2017, 11:56 AM   #298
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The best way to make planetary colonies is to fix the atmosphere, which would make Mars, with its smaller mass, less than ideal. We'd have to thin Venus' atmosphere instead. Not sure how we'd get to do that.
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Old 13th October 2017, 12:00 PM   #299
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Originally Posted by GlennB View Post
One event? I totally agree with what you say.

But the 'insurance' colony is much more likely to be wiped out by an event before it proves to be of any use in that respect.
You don't go as far as building a Mars colony and then stop at just one. Once you're there, the goal should be building the infrastructure to turn local resources into more colonies.
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Old 13th October 2017, 12:01 PM   #300
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Originally Posted by phunk View Post
You don't go as far as building a Mars colony and then stop at just one. Once you're there, the goal should be building the infrastructure to turn local resources into more colonies.
Would it be preferable to have a single big habitat or lots of small interconnected ones, I wonder? In the same vein, would it be better to have large space stations instead?
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Old 13th October 2017, 12:02 PM   #301
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Originally Posted by 3point14 View Post
You seem to be underestimating the size of the rock I am imagining.
You're imagining a scenario where the cost of mitigating the risk is to set up a fully self-sufficient human civilization on Mars. Biomass, ecosystem, industrial base, etc.

Humanity can't pull that off right now. Sending "colonists" to Mars right now is not a "first step" in that direction. Sometime in the future, humanity will reach a point where it is both feasible and practical to establish such a civilization on Mars.

This is not that point. This is the point at which, if we are lucky and Musk is right, it might be feasible to maintain a science outpost on Mars, much the way we maintain science outposts in the Antarctic.

But you're thinking too small: A black hole could collide with the sun, dooming our entire system. We should colonize another star right away.
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Old 13th October 2017, 12:03 PM   #302
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There aren't any rocks (that have any chance of hitting the Earth) big enough to make Earth less hospitable than Mars. Of course, there are plenty of moons and asteroids out there that are big enough for the job - but none in orbits where they could hit the Earth in the next million years or so.

Of course, there are plenty of rocks and comets* that would make a hell of a mess and kill off a lot of the life on Earth - but something like the impact that wiped out the dinosaurs still left Earth as an easier place to survive on than Mars is.

* People who talk about detecting space rocks a few years or decades ahead of impact and nudging them out of the way tend to ignore comets. A large comet that hasn't been anywhere near the sun during the time that humans have been around could be equally devastating - and we'd probably only see it coming a few months - maybe twenty months - before impact.
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Old 13th October 2017, 12:12 PM   #303
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Originally Posted by ceptimus View Post
There aren't any rocks (that have any chance of hitting the Earth) big enough to make Earth less hospitable than Mars.
There could be comets though.

edit: shouldn't have responsed before reading your whole post

Originally Posted by ceptimus View Post
A large comet that hasn't been anywhere near the sun during the time that humans have been around could be equally devastating
They could be MORE devastating, they tend to have significantly higher impact speeds.

Last edited by phunk; 13th October 2017 at 12:14 PM.
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Old 13th October 2017, 12:17 PM   #304
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Originally Posted by ceptimus View Post
* People who talk about detecting space rocks a few years or decades ahead of impact and nudging them out of the way tend to ignore comets. A large comet that hasn't been anywhere near the sun during the time that humans have been around could be equally devastating - and we'd probably only see it coming a few months - maybe twenty months - before impact.
I must ashamedly admit that I don't understand why they would be harder to detect.
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Old 13th October 2017, 12:23 PM   #305
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Originally Posted by Argumemnon View Post
I must ashamedly admit that I don't understand why they would be harder to detect.
Because they spend most of their time well beyond the orbit of Neptune where they are too far away and too dimly lit to be seen. At those distances the comets don't have a tail - they're just big balls of mostly ice - the tails only appear when they get nearer the Sun and begin to heat up. Then they begin to approach the Sun (and maybe Earth if we're unlucky enough to be in the firing line) and effectively fall in a more-or-less straight line towards it. By the time they get near enough to become visible (maybe between the orbits of Mars and Jupiter) they're already going really fast and don't give us much time to do anything about deflecting them.

Last edited by ceptimus; 13th October 2017 at 12:26 PM.
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Old 13th October 2017, 12:25 PM   #306
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Originally Posted by Argumemnon View Post
I must ashamedly admit that I don't understand why they would be harder to detect.
Asteroids have slow, circular, usually stable orbits that are easy to predict once detected. If we detect an asteroid that's going to hit Earth, it'll probably be in a few decades from now when the stars are right and everything lines up in just the right orbital position.

Comets show up because something nudged them out in the Oort cloud and caused them to come screaming into the inner system in tight, elliptical, cigar-shaped orbits. If a comet's going to hit Earth, it's already coming straight for us.
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Old 13th October 2017, 12:29 PM   #307
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Originally Posted by smartcooky View Post
Well that is only a matter of time now. I think we'll see flying cars, or more correctly, personal aerial transport, a lot sooner than you think. We already have many people who have flown personal airborne vehicles.
Really? Show me these personal airborne vehicles.

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One man's delusion is another man's vision. I guess you would have thought Werner von Braun delusional when he talked about rockets to the Moon.
I'm not sure who you think you are talking to. I've traced the development of the spacesuits, rockets, guidance, and life support systems. I'm familiar with Braun's ideas, most of which were not used. He proposed a space station that would spin to create artificial gravity. Never built. His concept for a lunar mission required the space station. His lunar lander would have to have been assembled in orbit over a period of eight months and would have weighed 8.7 million lbs. It was 160 feet tall and 108 feet wide and used 30 rocket motors. His plan was to send three of these vehicles to the moon. Two would carry 20 crew each. One would carry 10 crew and 259 metric tons of cargo. They would stay on the moon for six weeks. Then they would leave the cargo lander and return to the space station in the other two landers.

Hmmm, sounds an awful lot like that Musk Mars mission, doesn't it? And there's more. Those materials would have been delivered to the station using 15 space shuttles, flying 360 missions, carrying 33 metric tons each. Each shuttle was expected to have a turn around of 10 days. Hmmm, sounds an awful lot like ... the Space Shuttle program. Oh, and after this moon mission, Braun wanted to plan for a Mars mission.

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Oh, I see. I think of foothold as having a base of some kind. Apparently, you use the term to mean visited. I guess by your definition we have a foothold on the top of Mount Everest and the bottom of the Mariana Trench.

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► 65 launches per year promised
This schedule is a 20 day turnaround. That would be double Braun, the visionary's estimate. Apparently his vision was a bit cloudy.

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► 1/100,000 failure rate promised - 1/67.5 delivered.
You do understand that this is half the failure rate of Falcon 9, right?

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That is only because there were a limited number made.
No, I've already explained this to you. It's because they were hand-made which was the only way possible in the 1960s.

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The first few SpaceX Merlin engines cost about $30 million each to make. Now they run out at about $2.2 million each...they have built a total of 52 Falcon 9 rocket cores so far... that's 468 Merlin Engines... its a concept known as mass production, maybe you've heard of it.
The Merlin 1C was first tested in 2007. NASA delivered the first F-1 in 1963. There's something separating these two. It's called time, maybe you've heard of it. Technology advanced considerably in 44 years. We don't build engines by hand today. Last but not least, the F-1 is a 1.5 million lb thrust design, something SpaceX is unlikely to ever be able to design or build. They've already degraded the thrust of the Raptor.

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Now imagine they had continued developing the F1 from the start rather than taking a 40 year hiatus and having to resurrect everything again.
There was no mission for Saturn V at that time. The only space station being considered was Skylab.

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Look, I get that you are a hater and all that have no counter arguments so I'm going to resort to name calling, but do you really believe that the human race will never venture out into the the Solar System, and that we will always be resident only on this planet for the next million years?
A million years is a long time. I suppose if someone developed faster than light travel, anything would be possible. Short of that, I can't imagine humans ever making it out to Pluto on any kind of mission. A mission to Mars or the asteroids should be at least possible to design with current technology. I'm not sure though. I would say it's a tossup whether humans or human-level robots get there first.

I've read countless science fiction scenarios about teraforming Mars which can't be done. I've read stories about supplying water from comets or asteroids. I'm not sure how realistic that is. There were stories about colonizing Jupiter's moons. I think what you have to ask is what reason there would be to set up a base. We don't have a base on the moon even though it is possible because there isn't any compelling reason. We have even less reason to go to Mars.
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Old 13th October 2017, 01:20 PM   #308
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Back to water on Mars ...

One of the jobs of the first (twin landing) wave of this mission is to "prospect for water". Damn right, too. It will be needed for the Sabatier process to manufacture methane, LOX (electrolysis producing H2 for methane also produces O2, which is very handy) plus O2 for breathing, drinking water and eventually water for hydroponic systems and others.

Prospect. That word worries me. There certainly is water, though it varies in its distribution. With a 150t payload per ship there's room for a hefty, relatively capable prospecting rover or three, but what if the nearest viable water source is 10km away? 500m away? Then there's the energy cost of digging and purification (Mars' water is very saline, I read, and electrolysis units will not be happy about that. Boil off and condense the water content of the soil?).

Do you produce H2O and O2 (according to your projected need) in situ and ship back to base, or haul the raw material and produce H2O and O2 back at base? What's the energy cost of shipment, in either case? Man, I'm seeing some serious numbers of solar panels here, even before we start the Sabatier process. The former requires heavyweight robotics, while the latter also must include major robotics but allows human effort for the trickier parts. Or build human habs out at the 'water mining site' and transport the people, then the product back to base?

However, having identified a suitable water-bearing site (if there is one in reasonable range at all) you could land subsequent ships close by, to make things a lot easier. Though then you'd have the first two ships in need of refuelling from a site that's some distance away.

Sure, the ships won't land empty, but their CH4 and O2 total load amounts to 1100t. However much the top-up (is 500t crazy generous?) you'll have to dig, process and haul an awful mass of stuff to produce that 500t. On solar-powered kit. What kit? Are SpaceX developing such diggers and processors? Are there prototypes? What do they look like? Enquiring minds want to know!

Bottom line (for me) - you don't send a single soul up there, nor waste any money/effort on extra rocketry, until you know for sure you have the water/O2/CH4 issue cracked. And that revolves around a solar power issue that makes powering the Sabatier process look like a stroll in the park, because digging and processing the water requires major physical intervention whatever way you look at it.

Think 12v battery on your car. It takes several hours to trickle-charge it from a mains supply (read:Sabatier process), but you'll run it flat in a minute if the car won't start (read:lug materials over the Martian surface)
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Old 13th October 2017, 01:21 PM   #309
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Originally Posted by Argumemnon View Post
Would it be preferable to have a single big habitat or lots of small interconnected ones, I wonder? In the same vein, would it be better to have large space stations instead?
Tunnels. The Boring Company isn't a coincidence either. Although I'm sure the naysayers will now poo-poo that idea now.

Originally Posted by barehl View Post
SpaceX is unlikely to ever be able to design or build. They've already degraded the thrust of the Raptor.
Because the twr optimized in that direction. But I guess it's easier to snipe when you're not really paying attention.
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Old 13th October 2017, 01:29 PM   #310
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Originally Posted by ceptimus View Post
Because they spend most of their time well beyond the orbit of Neptune where they are too far away and too dimly lit to be seen. At those distances the comets don't have a tail - they're just big balls of mostly ice - the tails only appear when they get nearer the Sun and begin to heat up. Then they begin to approach the Sun (and maybe Earth if we're unlucky enough to be in the firing line) and effectively fall in a more-or-less straight line towards it. By the time they get near enough to become visible (maybe between the orbits of Mars and Jupiter) they're already going really fast and don't give us much time to do anything about deflecting them.
Originally Posted by Beelzebuddy View Post
Asteroids have slow, circular, usually stable orbits that are easy to predict once detected. If we detect an asteroid that's going to hit Earth, it'll probably be in a few decades from now when the stars are right and everything lines up in just the right orbital position.

Comets show up because something nudged them out in the Oort cloud and caused them to come screaming into the inner system in tight, elliptical, cigar-shaped orbits. If a comet's going to hit Earth, it's already coming straight for us.
Ok so it's a matter of predictability, not visibility.
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Old 13th October 2017, 01:34 PM   #311
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Originally Posted by Argumemnon View Post
Ok so it's a matter of predictability, not visibility.
It's both. NEOs are more visible than outer solar system objects.
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Old 13th October 2017, 01:43 PM   #312
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Originally Posted by smartcooky View Post
Where were the demands for Richard Branson to come up with the numbers to prove that his Virgin Galactic is a viable concept?
Branson hasn't done anything yet except try to piggyback on the success of SpaceShip One. They lost the first prototype SpaceShip Two. I think the second one has done glide testing. So, it's about on par with Dream Chaser except they actually have a NASA resupply contract for Dream Chaser. So, Dream Chaser should have funding through orbital testing and at least a few actual flights. I'm not sure if SpaceShip Two is even supposed to be orbital. And I can't tell if it's just a thrill ride or if he plans anything practical. I also have strong doubts about his collaboration with Boom Technology to build another supersonic transport.

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Where are the demands for calculations and details from NASA for their manned Mars plans?
What manned mission to Mars? Back in 2014, NASA had a statement about wanting to go to Mars sometime in the 2030's. To the best of my knowledge NASA is not currently designing either ships or landers for such a mission. If you look at the proposed schedule it had a shakedown of the DeepSpace Transport in 2029 which would be assembled in 2027 - 2028 at the DeepSpace Gateway which would be built in 2021 - 2026. Then you would have a Mars mission in 2036. I don't think they've put out any contracts for either the Deep Space Transport or the Deep Space Gateway. I assume the SLS test flight in 2019 is funded. Let's look at what is actually going on.

Phase 1: NASA is currently working on upgrades to the Orion habitat module that would allow it a duration of 60 days. Seven companies were selected for proposals. They are also working on heftier electric propulsion. Three companies were selected for this. And you have two companies working on CubeSat.

Phase 2: NASA asked for proposals for a long duration habitat. There are six companies working on this.

Phase 3: This would be hardware. Presumably selection on the long duration habitat won't happen until the concepts are completed in September, 2018.

The current concept is that the habitat would be like the Destiny lab module on ISS since it was designed to last years in space. This module is 28 feet long and 14 feet wide. Then you add the slightly shorter MPL module that was carried on the Space Shuttle. But we'll have to see what the companies come up with. The long duration habitat and the electric propulsion would be two parts of the Deep Space Transport. You still need main engines and fuel tanks.
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Old 13th October 2017, 01:58 PM   #313
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Originally Posted by Pixel42 View Post
I would estimate that 99% of Brits know who Richard Branson is. Maybe 5% know who Elon Musk is.
They were smart enough to pick up Tubular Bells at the fledgling Virgin Records when no other record company wanted it. It sold 3 million copies and made Virgin Records. I assume he is still involved with Virgin Airlines. He has made several long distance balloon flights and once tried to sail around the world on a large sailboat. His venture with SpaceShip One is called Virgin Galactic.
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Old 13th October 2017, 02:01 PM   #314
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Originally Posted by Octavo View Post
Why do you make the assumption that people will be returning? It's true that the system has the capacity to take a few people back, but Musk has been clear about this several time. It's a one-way trip for the humans.
I don't see this ever happening. If this is what Musk thinks then he's got a few screws loose.
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Old 13th October 2017, 02:04 PM   #315
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Originally Posted by Octavo View Post
Tunnels. The Boring Company isn't a coincidence either. Although I'm sure the naysayers will now poo-poo that idea now.
According to a recent BBC Horizon programme there are plenty of caverns and lava tunnels on Mars.

ETA link: http://www.bbc.co.uk/programmes/p05fjpcr
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Old 13th October 2017, 02:04 PM   #316
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Originally Posted by smartcooky View Post
There are people who are visionary, and have the ability to see some of their visions through to reality. Then there is The Great Knocking Machine...
Normally this would work, but saying it with me in this thread carries enough irony to take the flesh off your bones. Seriously?
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Old 13th October 2017, 02:13 PM   #317
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Originally Posted by GlennB View Post
6 ships leaving, one (arbitrary minimum) returning. Makes (6*5)+4 booster launches all told, assuming 100% reliability. If you want more of those 6 ships back then add 4 more tanker launches per ship. Now, the project might well generate more trade for SpaceX at existing levels, or boost the market for space launches and drive up the amount of business in total, but the project is going to be fantastically expensive to reach that point. And that isn't me saying that, it's SpaceX. And that's without looking into technical issues on Mars itself. We were talking about water up there ...
Remember, we are only talking propellent here; a very small part of the cost of a launch. It doesn't cost you the price of your whole car for every tank of fuel you buy. When you take Mrs GlennB and the little GlennBs off for your family holiday to Grand Teton, do you include the purchase cost of your $39,000 Dodge Durango in your budget?

Each BF Tanker merely has to keep enough fuel on board for a deorbit burn and a landing burn. Same applies to returning BFR-SM from Mars... they won't need a whole fuel load, just enough to get down. They certainly will not need four tankers per returning BFR-SM to have enough for deorbit and landing.

Again, I repeat this for nth time, there is nothing wrong with the concept per se. You are asking for details where no details exist. Let me make this a nice simple example for you;

I propose sending a wheeled vehicle out to do an unspecified job somewhere. Lets say its to and from a place where there are no gas stations on route. I can only carry X amount of fuel and it won't be enough to go there, do the job and make it more then 3/4 of the way back. My plan is to use another identical wheeled vehicle carrying a full fuel load to meet the returning vehicle at the 3/4 point and transfer sufficient fuel to return both vehicles to base. Its a plan which I am confident will work.

However, you are not so sure. I haven't provided you any calculations to show how this will work. I haven't proved to you that I can successfully transfer fuel

In fact, you are asking irrelevant questions, because I haven't even said what vehicles will be used, or how much fuel they carry or what their fuel consumption is. All I have done is outline an overall plan to solve a problem.

Now do you understand?
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Old 13th October 2017, 02:20 PM   #318
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Originally Posted by barehl View Post
Normally this would work, but saying it with me in this thread carries enough irony to take the flesh off your bones. Seriously?
Sorry, who are you again?

From my perspective, you are just some guy on the web who calls himself "barehl: Master Poster".. oooooh! impressive name, but you seem no more qualified that anyone else here.
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Old 13th October 2017, 02:28 PM   #319
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Originally Posted by barehl View Post
Branson hasn't done anything yet except try to piggyback on the success of SpaceShip One. They lost the first prototype SpaceShip Two. I think the second one has done glide testing. So, it's about on par with Dream Chaser except they actually have a NASA resupply contract for Dream Chaser. So, Dream Chaser should have funding through orbital testing and at least a few actual flights. I'm not sure if SpaceShip Two is even supposed to be orbital. And I can't tell if it's just a thrill ride or if he plans anything practical. I also have strong doubts about his collaboration with Boom Technology to build another supersonic transport.
All very interesting I'm sure, but none of it answers my questions.

Has anyone asked him to provide calculations to prove the veracity of his plans?. If so, where are they; if not, why not?

Originally Posted by barehl View Post
What manned mission to Mars? Back in 2014, NASA had a statement about wanting to go to Mars sometime in the 2030's. To the best of my knowledge NASA is not currently designing either ships or landers for such a mission. If you look at the proposed schedule it had a shakedown of the DeepSpace Transport in 2029 which would be assembled in 2027 - 2028 at the DeepSpace Gateway which would be built in 2021 - 2026. Then you would have a Mars mission in 2036. I don't think they've put out any contracts for either the Deep Space Transport or the Deep Space Gateway. I assume the SLS test flight in 2019 is funded. Let's look at what is actually going on.

Phase 1: NASA is currently working on upgrades to the Orion habitat module that would allow it a duration of 60 days. Seven companies were selected for proposals. They are also working on heftier electric propulsion. Three companies were selected for this. And you have two companies working on CubeSat.

Phase 2: NASA asked for proposals for a long duration habitat. There are six companies working on this.

Phase 3: This would be hardware. Presumably selection on the long duration habitat won't happen until the concepts are completed in September, 2018.

The current concept is that the habitat would be like the Destiny lab module on ISS since it was designed to last years in space. This module is 28 feet long and 14 feet wide. Then you add the slightly shorter MPL module that was carried on the Space Shuttle. But we'll have to see what the companies come up with. The long duration habitat and the electric propulsion would be two parts of the Deep Space Transport. You still need main engines and fuel tanks.
Again, this is all very interesting, but none of it answers my questions.

Has anyone asked them to provide calculations to prove the veracity of their plans?. If so, where are they; if not, why not?
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Old 13th October 2017, 02:40 PM   #320
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Originally Posted by phunk View Post
SpaceShipOne doesn't go anywhere near orbit. It reenters at very low speed compared to the shuttle.
It reached 112 km altitude. Obviously, the feather wouldn't work for orbital velocity. I know that Mercury Redstone 3 did have a heat shield but it reached 187 km. I suppose he would have had more velocity by the time he reached the Karman Line. Still, it seems like the capsule drag would have been much lower for the mass.
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