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#551 Re: Interplanetary transportation » Un- conventional ways to LEO » 2006-09-23 18:24:40
A massive laser is difficult because of the size of the components, the power storage systems (capacitors, flywheels), and directing optics.
I'm assuming a launch system would have a dedicated nuclear power plant. I know the optics get harder when you get larger, but I've got to believe that experience with segmented telescopes makes it easier
First the launch vehicle still needs some kind of reaction mass thus limiting specific impulse to ~1000sec for Hydrogen, and kind of defeating the purpose. Maybe a little higher with an ablator.
One proposal I saw had a dimpled plate while in the atmosphere - which gives good thrust from heated air - then the plate is jettisoned to expose an ablative plate once you're out of the atmosphere.
The beam itself will be absorbed and scatterd by the atmosphere that will make accurate/efficient transmission difficult, you can probably hit the vehicle, but you want to heat only the collector and not the whole thing.
Again, I'm thinking that adaptive optics like the astronomers use to correct for atmospheric effects can be helpful here. It does make the system more expensive, but one costing I saw quoted +20% (and not +200% or anything).
And finally the time that a vehicle will be overhead of the laser site will be short, which nessesitates extremely high (>10G) acceleration rates to get to orbital velocity before the vehicle goes over the horizon. This also really magnifies the power requirements of the laser to extreme levels.
Yeah, cargo only, probably looking at 20 ton payloads. $/kg looks nice though. And we need most of the tech for the space elevator anyway - to power the climbers.
Oh, and the ISS would make a terrible counterweight for a momentum exchange tether, its all the wrong shape for it and is in the wrong orbit.
That's a great idea! I knew you'd come around 
#552 Re: Interplanetary transportation » External Fuel Burning Propulsion » 2006-09-23 18:04:03
You're mose welcome. Yeah, maybe today it would look more like an X-43. I don't think they went far with external combustion before figuring out they could get better performance with a shroud.
#553 Re: Interplanetary transportation » Un- conventional ways to LEO » 2006-09-23 15:30:30
I like the laser propulsion ideas, except for that the laser has to be so powerful and therefore expensive.
Why are lasers so expensive? Is it just the (probably nuclear) power supply? Is the (probably adaptive) optics? What would make them cheap? More SDI research?
#555 Re: Not So Free Chat » Has Multiculturalism Failed ? » 2006-09-23 15:11:47
You could call it the North American Co-Prosperity Sphere.
#556 Re: Interplanetary transportation » Earth to LEO - discuss » 2006-09-23 12:55:52
I have no personal intrest in traveling at reletevistic velocities, holding out for FTL
, so I leave you on your own to figure out the magsail. One thing that does intrest me about them is that once I read an article somewhere that claimed besides their thurst they provided excellent radiation shielding. Wish I remembered where that was...
May be hereish ...
http://www.newmars.com/forums/viewtopic.php?p=84792
Tom's right about the magsail being the solution to slowing down at the destination star - very nice properties like faster you're going the better it works ...
http://www.niac.usra.edu/files/library/ … Zubrin.pdf
Another interstellar sail idea: the sail is a relatively smallish square of uranium. It tows a box of antimatter which is released at the sail. The collision causes a smallish nuclear reaction, ablating the sail and providing thrust. Has an Isp of a million seconds ...
#557 Re: Interplanetary transportation » External Fuel Burning Propulsion » 2006-09-23 11:31:34
The first message in this discussion may be of assistance ...
#558 Re: Meta New Mars » Spammer » 2006-09-23 03:23:59
MMF spammer. Haven't seen one of those in a long time.
#559 Re: Science, Technology, and Astronomy » Protein folding pathway brought back in the mix? » 2006-09-22 22:46:35
Well, this new development actually hasn't been confirmed yet anyways; but even if it does work out, I find it remarkable researchers didn't think of this earlier;
The problem is that you have to do these search optimizations really carefully otherwise you're guaranteeing you'll miss global optima (in this case, how the proteins actually fold as opposed to how you now think that they fold).
just comes to show that Humanity is facing some human thinking and computational limitations as it progressed towards the future.
For all intents and purposes, we have infinite computational needs
#560 Re: Not So Free Chat » Bow Down Before Iran? » 2006-09-22 19:26:36
Welcome aboard Steve.
#561 Re: Meta New Mars » Spammer » 2006-09-22 03:19:43
My first spammer ...
#562 Re: Science, Technology, and Astronomy » General Relativity confirmed accurate to 0.05% » 2006-09-22 02:50:52
Does that mean that if you want more accuracy relativity is no good or does it mean that they verified it to that accuracy but haven’t found a suitable test for more accurate verification.
The latter. If you think you've found a GR violation greater than 0.05%, you're going to have a lot of convincing to do.
#563 Re: Unmanned probes » Mars Express (MEX) - ESA orbiter » 2006-09-22 02:33:13
Has the MARSIS data been released/published/submitted for publication?
#564 Re: Not So Free Chat » Bow Down Before Iran? » 2006-09-22 00:46:12
I keep the basic facts in my head and ignore the speeches, basically the Iranians, Lebanese and the Syrians started the War with Israel, and no amount of talking and propaganda is going to make me believe that the Israelis are responsible for that war. The Muslims have the Jews outnumbered by a considerable amount, hence the Israelis first priority is toward survival, with sparing the civilian lives of their attacking enemies being a distant second. The Israelis certainly cannot afford to lose one soldier for every terrorist they kill, it is simple mathmatics, hence they will want to use weapons that keep their enemy at a distance, these weapons unfortunately also kill some civilians, but Israel didn't start this war.
The modern state of Israel has been at war with its neighbors literally since day one. To speak of who "started" the most recent action is ludicrous.
#565 Re: Meta New Mars » We need new moderators » 2006-09-21 18:29:32
Yeah, was going to add you actually, love the stuff you're doing on the wiki.
Thanks, I love the wiki format. One day I'll be able to settle interminable arguments with a reference to a wiki page - but humans will probably set foot on Mars first.
I feel bad for not being around lately. Added.
I went on walkabout for six months (which I thoroughly recommend, by the way), so I'm not really one to judge
I'd add RobertDyck and GCRNRevenger (since they're here a lot), but I think they'd be deleting each others posts or something! :twisted:
Nonsense, they are both perfect gentlemen and should be co-opted immediately.
#566 Re: Meta New Mars » We need new moderators » 2006-09-21 15:25:39
I'm happy to delete spammers if you like.
#567 Re: Human missions » Red Planet Capital » 2006-09-20 15:46:03
NASA wants to give you money ...
http://www.redplanetcapital.com/
Here's the associated RoI for the fund ...
http://www.spaceref.com/news/viewsr.html?pid=19532
$11 million in 2006, $20 million per year thereafter (hey, it's a start)
Presentation by the fund tomorrow at AIAA Space 2006
• Focus:
* Nanotechnology
* Robotics
* Intelligent Systems
* High-speed networking and communication
• Current Mission Needs:
* Innovative Human Enhancements for Exploration
* Water Recycling, Reuse, Reduction
* In Situ Fabrication of Replacement Parts Technology
* Environmental Monitoring, Control and Revitalization
* Communications and Data Systems
#568 Re: Not So Free Chat » Bow Down Before Iran? » 2006-09-18 09:36:55
Why are we aways the first to forgive, the first to understand, they first to help our enemy back up on his feet and to help him rebuild?
Because we absolutely dominate the world. We won. The US can vaporize any other nation on Earth. At will. Economically, militarily, technologically, in every possible area of power, no one can possibly rival the US for 50 years, minimum. It is a situation unprecedented historically. Such a nation automatically has enemies, but our enemies are so powerless they are forced to resort to ignoble asymmetric warfare. They can never win and they can't even really damage us unless we damage ourselves by overreacting. We are generous because we can afford to be and because it is harder to recruit suicide bombers from among those who have hope for a better future for themselves and their families.
Islam is not a monolithic groupthink cult, just as Christianity is not a monolithic groupthink cult.
All the evidence I see on telivision seems to suggest that it is.
Stop watching tabloid television?
I do not see the Muslim equivalent of peaceniks that seem so prevalent in our society.
I'll see what I can do to get them more air time.
There is no equivalent to fundamentalist Islam in Christianity, nothing in christiandom approaches the scale and violence of fundamentalist Islam, nothing, there may be a few cults here and there, but nothing that has seized control of entire societies and has enforced religious blue laws with violence and harshness that approaches the Muslim Shaira.
"We have enough votes to run the country. And when the people say, "We've had enough," we are going to take over."
-- Pat Robertson, speech given to the April, 1980 "Washington for Jesus" rally
"If Christian people work together, they can succeed during this decade in winning back control of the institutions that have been taken from them over the past 70 years. Expect confrontations that will be not only unpleasant but at times physically bloody.... This decade will not be for the faint of heart, but the resolute. Institutions will be plunged into wrenching change. We will be living through one of the most tumultuous periods of human history. When it is over, I am convinced God's people will emerge victorious."
-- Pat Robertson, Pat Robertson's Perspective Oct-Nov 1992
"There is no such thing as separation of church and state in the Constitution. It is a lie of the Left and we are not going to take it anymore."
-- Pat Robertson, address to his American Center for Law and Justice, November, 1993.
"Ladies and gentlemen, I want to say this very clearly. If the people of the United States -- all across America, in their churches and in their civic groups and in their legislatures -- decide that they're not going to allow the Supreme Court to dominate their lives in the fashion that it has been in this nation, the Supreme Court does not have the power to change that. They are not going to be able to overturn the will of a hundred million American people. And I think the time has come that we throw off the shackles of this dictatorship that's been imposed upon us.
We had a war in 1776 that set us free from the shackles of the arbitrary rule of the British crown, and I think what's going on in Corbin, Kentucky, boy, those people like to live free. And I think the time has come that we do that..."
-- Pat Robertson, The 700 Club television program
"Individual Christians are the only ones really -- and Jewish people, those who trust God of Abraham, Isaac, and Jacob -- are the only ones that are qualified to have the reign, because hopefully, they will be governed by God and submit to Him."
-- Pat Robertson, The 700 Club television program
etc
etc
etc
#569 Re: Not So Free Chat » Bow Down Before Iran? » 2006-09-18 01:06:52
So say Lindsey popularized the idea. Any chance the Ayatollah or Osama picked it up and said, “hey that is not a bad idea”. Also does it have any basis in the Muslim text by some sort of skewed interpretation or another. So say I can discredit Lindsey. Can I discredit Glen Beck as well?
I'm sure Lindsey got the idea from his equivalent in Islam. No religion has a monopoly on fruitcakes.
Islam is not a monolithic groupthink cult, just as Christianity is not a monolithic groupthink cult. There are vicious fundamentalists on both sides that urgently need reeducation. Islam is currently going through the same crisis that Christianity went through two or three generations ago. Women want the vote, the kids want their MTV, people don't go to the mosque as much anymore. Add to that a high proportion of young men in the population and a high youth unemployment rate and you've got the conditions for revolution. The mullahs are fighting tooth and nail for the deal they've had for centuries, the government is looking to focus all that dissatisfaction on someone other than themselves - Israel and the US have been convenient scapegoats for a long time now. This is not healthy, but Israel and the US haven't exactly been making their job difficult of late. It is going to take a couple of generations for them to process the whole change, just like it did in the West. Afterwards, the world will have billions of new consumers and everyone except the environmentalists will be happy. In the meantime our goal should be to minimize the number of people that get killed or have their lives ruined to the extent that they embark on multi-generational vendettas.
#570 Re: Human missions » Ares and Ares » 2006-09-17 23:38:32
Imagine a solar-powered laser cutting torch in the vacuum of space. (I'm reminded of the qarish paintings on some covers of Wonder Stories and other pulps of the 1930's, in which passenger spaceships are depicted horribly being cut into sections by beam weapons, with the beams brightly coloured of course. How about situating our prospecting ship some distance from a rotating asteroid, and slicing it into manageable hunks as it rotates, just like a baloney sausage?
I don't think solar can do it. Some quick googling yields 0.01 kWh per cubic centimeter as the energy required to "spall" rock (apparently you don't want to melt it because then it'll quickly reset as a tough ceramic). The energy required can vary up or down an order of magnitude depending on the type of rock. So, say you have a Star Wars style CO2 laser with a power conversion efficiency of 30% (state of the art for high power lasers, although diode lasers exist with efficiencies of 65% and there are promises of 80%) hooked up to a 50 MWe nuclear reactor. It'll take you 31 weeks to make a 1 cm thick cut through an asteroid 1 km in diameter (53 hours if the asteroid is 100 meters in diameter).
This sounds reasonable, especially if you are just cutting out "cones of interest," but solar today gets about 0.1 kW/kg, so you'd need 500 tons of panels to get 50 MWe. They are trying to get that down to 1 kW/kg with thin film solar - so maybe you could do 10 MWe for 10 tons by 2025.
Of course, you don't need nuclear or solar, because a rotating asteroid is a huge flywheel (albeit an irregularly shaped one). Generator + contact wheel + rotating asteroid = as many MW as you can eat at 2 kW/kg off-the-shelf (3 kW/kg by 2010).
#571 Re: Not So Free Chat » Bow Down Before Iran? » 2006-09-17 22:18:15
I’ve been bothered by a lack of sources on the internet about the “third great Jihad”. It seems most of the sources just rehash the same article
written by the bona fide fruitcake Hal Lindsey who has made no secret of the fact that he is actively working to bring about a religious apocalypse. That's pretty much all the knowledge you need to decide whether to thoughtfully study the original article or to have it scheduled for internment at Yucca Mountain.
#572 Re: Life on Mars » Life found to exist in driest parts of Atacama desert. » 2006-09-17 02:32:31
Especially since you can get some liquid water at -50 celsius if it is saturated with calcium chloride (-20 with sodium chloride aka table salt). The average temperature at the Viking sites was -57. It is colder at the poles though.
#573 Re: Science, Technology, and Astronomy » Mercury Mirror Space Telescope » 2006-09-17 02:07:27
The whole assembly can be moved about slowly with a small reaction control system to allow it to image any location in space at any time.
The "any position at any time" claim seems to be contradicted by the requirement that the "slow" rotation in the plane containing the tethers remain constant. Say I want to look at something between the two counterweights, don't I have to wait for a full rotation before I can see it again?
Also, won't the repositioning movements cause ripples on the mirror due to acceleration and deceleration?
#574 Re: Human missions » I had ENOUGH! Project Pegasus is now... » 2006-09-17 00:29:39
Anyone here know more about 4 Frontiers?
Robert gave a bit of their history here ...
http://www.newmars.com/forums/viewtopic … 2&start=68
and their website says that they are going to report on their progress in the next few days at AIAA's Space 2006 conference in the next few days.
They were supposed to build an outreach center, but they seem to have scaled back to a web store ...
4Frontiers is creating an initial webstore product line that includes education packages, books, clothes, toys, games and other Mars and space items related to our informative entertainment business segment.
Have they published anything this year?
#575 Re: Interplanetary transportation » Un- conventional ways to LEO » 2006-09-16 21:44:19
No, please, this one is just bullshit ...