So it was the last thing Armstrong stood on before be went to the moon. Wow. Should we also cut out the last piece of ground he stood on and move it to a museum? Or how about the vehicle he drove to the pad?
The tower is not an engineering feat unto itself. It has no historical value other than "there was a big rocket sitting next to this at one time, but we can't show you that because it's gone."
For what it's worth, I do wish we had real flight vehicles to display. If the Apollo 11 Saturn V still existed, I'd be the first to say "let's restore it!" But it doesn't, and saving a little bit of scaffolding is not going to bring it back. A much better testament to the hard working men and women of the Saturn program would be to go forward into space. Even Von Braun wanted an Orion to take us to the planet Saturn. (Boosted into orbit on top of a Saturn V, of course.) For all the bad rap people have given him, he wasn't stupid. He knew that the chemical rockets couldn't manage manned interplanetary missions. But they could handle getting things to orbit where a space economy could begin.
It's one thing to save the Saturn V, or the Apollo crew module, but why does anyone find the tower significant? It's a bit like trying to save the construction elevator for the Empire State Building, long after the building is gone.
I understand that the tower has certain sentimental value to the astronauts. After all, their craft sacrificed themselves to send astronauts into orbit, or to the moon. The tower is all that's left of those glorious machines. But isn't that like keeping a death grip on a ring or hair locket long after a spouse has died? Physiologically, one has to accept the fact and move on. Doing otherwise would only be detrimental to the individual.
Shouldn't the astronauts let go of the tower and spend their time instead promoting one of the hundreds of high energy propulsion methods available? Wouldn't the best testament of the Saturn V be a thrust into space rather than shaking our heads and saying, "it was fun while it lasted?"
NERVA, GCNR, Nuclear Salt Water, Orion, Daedalus, Fusion rockets, terrawatt laser launchers, etc., etc., etc. We have the technology for crying out loud. Let's make the Saturn program proud. Let's go forward!
The Seawolf has a crew complement of 12 officers and 121 enlisted personnel for a total of 133 crew members. She's certainly no slouch.:-)
I suppose if we're just talking about a passenger shuttle craft, it doesn't have to be as big as all that in order to carry lots of people. The reason the shuttle has to carry so much 'dead weight' is because it has to support the crew for awhile when it gets up there, but if it could just go straight to orbit and dump its payload of passengers, it can probably be a bit smaller and still carry plenty of people.
Actually, a large portion of the shuttle's weight is allocated to its cargo. I've been in one of the shuttle mock ups and they have MASSIVE cargo bays (about the size of a school bus). According to one source they can carry up to 8,605 kg (18,970 pounds) of mass to the space station when the bay is pressurized. Assuming an average weight of 200 lbs. per person, plus another 3 tons for a special passenger module for the cargo bay, you could carry about 64 people per flight. Throw in a little extra weight for various incidentals and you could probably arrive at a reasonable figure of 50 passengers per flight.
The Seawolf is actually pretty small compared to a deep-space vehicle, I think, because of that one small thing. Sure, you could stick some ion drive units on there powered by the nuclear plant, but how fast would it go, then? How long would it take to accelerate? That's the real question.:)
Small? At 353x35x40 feet, she'd be plenty large for a space born vehicle. In comparison, a two bedroom camper with kitchen and toliet is 40 feet long and about the width of a conversion van. Since a peaceful space vehicle wouldn't need so many crew (no battlestations), it would be as good as a luxury liner.
As for thrust, the Prometheus for the JIMO mission thrusts about 1 newton per second (one kilogram of acceleration per second) on a 10 megawatt reactor. According to the navy's specs the PWR/S6W reactor on the Seawolf can put out 220 megawatts of power. Assuming a linear increase in power, that would give our fictional Spacewolf a thrust of 22 Newtons.
Of course, I doubt that the military would be happy with 22 newtons of thrust. They'd probably want a more powerful fission drive. Options include NERVA, GCNR (Gas Core Nuclear), Nuclear Salt Water, and Orion drives. All of those have a very high thrust in exchange for a lower Isp than Ion drives. However, their Isp is still significantly higher than today's chemical rockets, and yet they can produce comperable thrust.
I'm curious enough about this that I'd be interested in seeing a breakdown of how much each component and system of the Seawolf-class sub weighs. I don't want anything classified, of course, but if someone can give this information I'd really be interested in seeing it.
I seriously doubt you'd get anywhere near those specs. However, if you strip out the weapons, the ballast tanks, the screws, the reactor rotors, the sonar and reduce the crew, you'll probably be able to save yourself a good fraction of the weight. Space versions of some of the above would have to be installed in orbit, but you're probably still saving yourself a bundle.
Of course, all of this is just facts and figures. None of this means that launching a Seawolf into orbit is a good idea, bu
Short of an Orion, the largest proposal I've seen is 3,000 tons. And part of that is rocket engine weight. If you launched multiple times and constructed it in space, it could be doable. (i.e. The hull in one launch, the reactor and some internals in the next, and the weapon systems and the rest of the internals in the last.)
Can a Seawolf deal with re-entry heats?
If you're going to launch something that big, I think you'd keep it up there. Not much point in a large reentry craft.
Re:NASA should contract the Navy
on
NASA's Own X Prize?
·
· Score: 2, Insightful
Let me guess you suggest launching rockets using nuclear reactors. It's called rocket fuel for a reason.
Actually, there are quite a few Nuclear Rocket designs. The most applicable to this situation would probably be NERVA or GCNR. Both could provide heavy lift capability as well as efficient space engines. You'd still need some sort of propellant to convert into plasma, but oxygen and hydrogen are fairly common gasses that can be found all over the solar system.
Also, im pretty sure that making a shuttle out of solid metal is just a bad idea.
The holy grail of space travel is having good enough propulsion to be able to make a space craft out of "normal" building materials like steel. The only reason NASA uses advanced composites is because of the weight issues.
The Orion craft is often hailed as a missed opportunity in part because of its ability to be built out of traditional materials. In fact, the Orion design actually becomes more efficient as it gets larger. The largest Orion ever proposed (within the confines of modern technology) was an 8 million ton starship.
Oh and last time I checked most "nautical vessels" still needed food and water.
That's why they carry food stores. Military vessels are equipped to operate with cut supply lines for months at a time. Granted, military vessels usually purify the water around them for drinking, but a space craft could get away with recycling and excess water stores.
Oh and lets also not forget all of those wonderful "submarine accidents". You kinda failed to mention them, eh?
You mean as opposed to all those space accidents? You kinda failed to mention them, eh?
Never mind that PC's have been saying this since 1982, for the exact same reason: You put an invalid or non-system (floppy) disk in the drive.
You do realize that error is the same one you get when a hard drive goes bad? Sure, I should have considered the floppy, but:
1. It was the weekend and my mind was elsewhere.
2. This was one of those laptops that swap the floppy and the cdrom drive. For some unfathomable reason, they had actually stuck the floppy drive in the laptop and used a floppy disk. Considering that no one does that anymore (even then) it just didn't hit me that they might have had a disk in the drive. At the back of my mind, I kept thinking that there was a cdrom drive installed.
So complain all you want, but you can only diagnose a problem over the phone if you have a proper picture in your mind. Otherwise it would end up taking longer over the phone than driving there, ejecting the floppy, and driving back. (Total time: about 1 hour.)
I hate to break it to you, but that's how free speech works. There's no constitutional protection for anonymity. If you want to be anonymous, you're going to have to do it on someone else's authority. (i.e. Someone who would be willing to protect your identity despite becoming a target himself.)
And before anyone says you'd never be put to death because of domiain information, realize that treason is a capital offense.
Two words: Public Outrage
That's why it's so important not to allow secret trials. And for the most part, judges are pretty good at keeping things on the up and up (no matter what the FBI or CIA wants).
...like it's a big deal. This is the type of law that would only get enforced when you really piss someone off. If you're running an illegal site, you can expect that they'll heap this charge on with the 1000 others they levy against you. Without a motive like illegal activity, it's difficult to prove that you were being intentionally misleading. (Unless you're dumb enough to fill it out with "Snoopy, 10 Charlie Brown Drive, Gotham City" that is...)
Actually, the disk gave the message about a bad disk. i.e. "Invalid or non-system disk."
That's why it sucked so much. It sounded like a failed hard drive, which was unlikely since the laptop was new. Although the look on her face when I ejected the disk was almost worth the trip.:-)
You mean, like their computer won't boot because they left a floppy in the drive? (Had to drive 20 miles to work on a weekend once, because someone had a big presentation to give. Stupid floppies.)
Of course, Kerry's specifically mentioned his opposition to outsourcing in the past...
That's not necessarily a point in his favor. The question is what he wants to do about it. If solution is to close off our borders and make us internationally unfriendly, then it's a point against him. We need a measured response to problems, not a "cut it off at the knees" response.
How do you do that if you don't know what time it is?
Cripes. The sun rises in the east and sets in the west. If you know if it's morning or afternoon (not tough) you can look to the direction of the sun. Follow the rest of the instructions from there.
Dean, Edwards, Clarks and Liebermans platforms are "Hey! We're not Bush either!"
But Kerry has something they don't: charisma
Oh, and somehow the term "Hitler" gets thrown out when talking about him. The way I figure it, he's already lost the presidency. He's got no platform, and he's already invoked Godwin's law. Not a great situation to find yourself in.
I was referring to the aerodynamics of the rocket. The 75,000 pounder already had the fluid dynamics worked out. Otherwise it wouldn't have been firing for a half-hour.
The Party has annointed him so Vote.A vote for anyone else in your primary or caucus is a vote for Hitle...uh BUSH!
Didn't see this coming. Nope, not at all. Kerry supporters are so non-predictable.
Now, would someone like to tell me what Kerry's platform actually *is*? So far it seems to be, "I'm not Bush, therefore I should be elected." What's his stance on space travel, copyright laws, abortion, education, deficit spending, etc, etc, etc.?! Oh, that's right. "I'm not Bush."
Sure, you can get an approximation by doing that, but the watch method is more accurate (though not as accurate as using a compass).
How can it be more accurate when all you do is point your watch hand in the approximate direction of the sun? It would be much more accurate to take a stick, plunge it upright in the ground, and use it as a sundial. Draw the east-west line of the sun, then cross it with a perpendicular line. The perpendicular line gives you North/South. Now you have exact angles to use for direction. Whenever you fear you're drifting, just stop, repeat, and correct your course.
Now, if someone could just tell me the point of knowing north when you're 100% absolutely lost with no idea what is in what direction...
Or you could just look at the sun, figure out which way is east and west, and by extrapolation figure out north and south. Or is it easier to remember how to turn your watch than which direction the sun rises from?
Enough said - nearly a prototype is not ready for action.
The full scale 250,000 lbs of thrust model was never built. However, the 75,000 lbs of thrust model was built, was tested, and (for a space only vehicle) could be used as is. You'd need either multiple engines or a longer burn to produce the same effect as the 250,000 lb version, but 75,000 lbs at 800 Isp with a 1/2 hour burn is still more than sufficient for a Mars mission.
You just can't say something is ready to fly when you have a scaled down model, if nothing else decades of scramjet development have shown that.
Arguably, a scramjet is far more difficult due to the requirement that it fly in an atmosphere. A NERVA engine for a Mars mission would have no such requirement. As long as the smaller engines could be shown to be space-worthy and reliable, there's no immediate need to scale them up, or even concern ourselves with the difficulties of constructing proper aerodynamics.
I used to work in materials science, working alongside people from a nuclear research facility and the advances haven't been as big as you would think outside of electronic materials. The high temperature and radiation resistant alloys that were in use 30 years ago are still the ones to use. The ceramics developed for the shuttle are still the cutting edge for heat sheilding as well.
And those materials are still way better than the steel and carbons they had in the 1960's. There's also been a lot more research into Plasma containment. Not yet enough to build a "magnetic bottle", but enough to better control the flow and output of the fuel.
It's likely that competing technologies, probably including NERVA will get some funding to see if they will work. Fortunately something of this scale will get enough attention that a good proposal is likely to be chosen, not just a politically expedient one.
NERVA was actually NASA's first choice for a Mars mission back in the 80's. Unfortunately, the public is just as afraid of nuclear technology today as they ever were. If you witnessed the protests over Cassini, then you would probably realize that it will take some gutsy NASA officials to approve a nuclear engine, even solely for space travel.
Still, I hope you're right. Otherwise we'll be stuck with lame ideas like an ION drive final stage, or shipping dozens of solid boosters into an orbital construction yard for use on a Mars mission.
Sorry, try again. You forgot the weight of the mountings, suspension, deployment units, etc. There's more to the solar panels than just the panelling itself. Weight adds up quickly when talking about structure support and reinforcement. (The entire rover weighs 174 Kg.) Motors to deploy the panels are no slouches either, although NASA is probably using a small motor similar to those on an RC car.
BTW, the Rover has a maximum power generating capability of 140 Watts. It takes two batteries to keep the rover running when there isn't enough sunlight. NASA doesn't say what kind of batteries they are (their "specs" on the rover are kind of useless), but external sources claim that they are Lithium Ion batteries with a weight of 7.15Kg a piece (8.77 Kg with the support struts). That same article claims that the rover needs a constant 100 Watts to operate.
Let's do some math shall we?
Design 1: We ditch the batteries all together, and use a 150 Watt RTG. We'll estimate it's weight is ~2Kg of plutonium, plus another 2 Kg of material for the rest of the device and the mountings. The net weight increase is (2 + 2) - (8.77 * 2) = -13.54 Kg.
Design 2: We use a 150 Watt RTG, but keep one battery for high draw situations. The net weight increase is (2 + 2) - 8.77 = -4.77 Kg.
One way or another, it's a win-win situation. Sorry, we're back to the "tree huggers" stopping RTG missions.
I think you're missing the point here. We *have* nuclear engine designs that are *known* to work. The NERVA engines were nearly ready for full scale prototypes before the project was wound down. These engines will give you high thrust (75,000-250,000 lbs.) combined with highly efficient fuel usage (800-1000 Isp). Full scale engines have burned for a full half hour! That's longer than any chemical rocket I'm aware of. Sure, 75,000 pounds of thrust isn't much when compared to a Saturn V, but for a Mars mission, that much power at a longer burn time is the difference between months and years of travel time.
Considering that it would be cheaper to finish development on NERVA than to resurect the Saturn V and improve it's output for a Mars mission, the choice would seem to be obvious. Plus, we have the added benefit of 30 years of materials and nuclear science development. Of course, I'd much rather see GCNR engines, but if you want it done fast, cheap, and effective, NERVA will do it.
Slashdot Mirror
So it was the last thing Armstrong stood on before be went to the moon. Wow. Should we also cut out the last piece of ground he stood on and move it to a museum? Or how about the vehicle he drove to the pad?
The tower is not an engineering feat unto itself. It has no historical value other than "there was a big rocket sitting next to this at one time, but we can't show you that because it's gone."
For what it's worth, I do wish we had real flight vehicles to display. If the Apollo 11 Saturn V still existed, I'd be the first to say "let's restore it!" But it doesn't, and saving a little bit of scaffolding is not going to bring it back. A much better testament to the hard working men and women of the Saturn program would be to go forward into space. Even Von Braun wanted an Orion to take us to the planet Saturn. (Boosted into orbit on top of a Saturn V, of course.) For all the bad rap people have given him, he wasn't stupid. He knew that the chemical rockets couldn't manage manned interplanetary missions. But they could handle getting things to orbit where a space economy could begin.
I *wish* JavaScript had Java like syntax. I can't count how many times I've typed this:
//do something with item
//do something with item
for(int i=0; i<length; i++);
when I meant to type this:
for(var i=0; i<length; i++);
or even worse:
function func1()
{
for(i=0; i<length; i++) func2(i);
}
function func2(item)
{
for(i=0; i<length2; i++)
}
when I meant to type:
function func1()
{
for(var i=0; i<length; i++) func2(i);
}
function func2(item)
{
for(var i=0; i<length2; i++)
}
(For those of you who don't know JavaScript, "i" will be global without that "var" definition.)
And V'Ger, Can't forget V'Ger.
You're not funny.
Physiologically, one has to accept the fact and move on.
Hmm... sometime even spell checkers can bite you in the ass. That should read "Psychologically, one has to accept the fact and move on."
It's one thing to save the Saturn V, or the Apollo crew module, but why does anyone find the tower significant? It's a bit like trying to save the construction elevator for the Empire State Building, long after the building is gone.
I understand that the tower has certain sentimental value to the astronauts. After all, their craft sacrificed themselves to send astronauts into orbit, or to the moon. The tower is all that's left of those glorious machines. But isn't that like keeping a death grip on a ring or hair locket long after a spouse has died? Physiologically, one has to accept the fact and move on. Doing otherwise would only be detrimental to the individual.
Shouldn't the astronauts let go of the tower and spend their time instead promoting one of the hundreds of high energy propulsion methods available? Wouldn't the best testament of the Saturn V be a thrust into space rather than shaking our heads and saying, "it was fun while it lasted?"
NERVA, GCNR, Nuclear Salt Water, Orion, Daedalus, Fusion rockets, terrawatt laser launchers, etc., etc., etc. We have the technology for crying out loud. Let's make the Saturn program proud. Let's go forward!
The main thing I'm thinking is that you need to be able to send lots of people at once. What's the crew capabilities on the Seawolf? I didn't check.
:-)
:)
(I'm quoting this fact file.)
The Seawolf has a crew complement of 12 officers and 121 enlisted personnel for a total of 133 crew members. She's certainly no slouch.
I suppose if we're just talking about a passenger shuttle craft, it doesn't have to be as big as all that in order to carry lots of people. The reason the shuttle has to carry so much 'dead weight' is because it has to support the crew for awhile when it gets up there, but if it could just go straight to orbit and dump its payload of passengers, it can probably be a bit smaller and still carry plenty of people.
Actually, a large portion of the shuttle's weight is allocated to its cargo. I've been in one of the shuttle mock ups and they have MASSIVE cargo bays (about the size of a school bus). According to one source they can carry up to 8,605 kg (18,970 pounds) of mass to the space station when the bay is pressurized. Assuming an average weight of 200 lbs. per person, plus another 3 tons for a special passenger module for the cargo bay, you could carry about 64 people per flight. Throw in a little extra weight for various incidentals and you could probably arrive at a reasonable figure of 50 passengers per flight.
The Seawolf is actually pretty small compared to a deep-space vehicle, I think, because of that one small thing. Sure, you could stick some ion drive units on there powered by the nuclear plant, but how fast would it go, then? How long would it take to accelerate? That's the real question.
Small? At 353x35x40 feet, she'd be plenty large for a space born vehicle. In comparison, a two bedroom camper with kitchen and toliet is 40 feet long and about the width of a conversion van. Since a peaceful space vehicle wouldn't need so many crew (no battlestations), it would be as good as a luxury liner.
As for thrust, the Prometheus for the JIMO mission thrusts about 1 newton per second (one kilogram of acceleration per second) on a 10 megawatt reactor. According to the navy's specs the PWR/S6W reactor on the Seawolf can put out 220 megawatts of power. Assuming a linear increase in power, that would give our fictional Spacewolf a thrust of 22 Newtons.
Of course, I doubt that the military would be happy with 22 newtons of thrust. They'd probably want a more powerful fission drive. Options include NERVA, GCNR (Gas Core Nuclear), Nuclear Salt Water, and Orion drives. All of those have a very high thrust in exchange for a lower Isp than Ion drives. However, their Isp is still significantly higher than today's chemical rockets, and yet they can produce comperable thrust.
I'm curious enough about this that I'd be interested in seeing a breakdown of how much each component and system of the Seawolf-class sub weighs. I don't want anything classified, of course, but if someone can give this information I'd really be interested in seeing it.
I seriously doubt you'd get anywhere near those specs. However, if you strip out the weapons, the ballast tanks, the screws, the reactor rotors, the sonar and reduce the crew, you'll probably be able to save yourself a good fraction of the weight. Space versions of some of the above would have to be installed in orbit, but you're probably still saving yourself a bundle.
Of course, all of this is just facts and figures. None of this means that launching a Seawolf into orbit is a good idea, bu
Can NASA put 7,700 tons into orbit?
Short of an Orion, the largest proposal I've seen is 3,000 tons. And part of that is rocket engine weight. If you launched multiple times and constructed it in space, it could be doable. (i.e. The hull in one launch, the reactor and some internals in the next, and the weapon systems and the rest of the internals in the last.)
Can a Seawolf deal with re-entry heats?
If you're going to launch something that big, I think you'd keep it up there. Not much point in a large reentry craft.
Let me guess you suggest launching rockets using nuclear reactors. It's called rocket fuel for a reason.
Actually, there are quite a few Nuclear Rocket designs. The most applicable to this situation would probably be NERVA or GCNR. Both could provide heavy lift capability as well as efficient space engines. You'd still need some sort of propellant to convert into plasma, but oxygen and hydrogen are fairly common gasses that can be found all over the solar system.
Also, im pretty sure that making a shuttle out of solid metal is just a bad idea.
The holy grail of space travel is having good enough propulsion to be able to make a space craft out of "normal" building materials like steel. The only reason NASA uses advanced composites is because of the weight issues.
The Orion craft is often hailed as a missed opportunity in part because of its ability to be built out of traditional materials. In fact, the Orion design actually becomes more efficient as it gets larger. The largest Orion ever proposed (within the confines of modern technology) was an 8 million ton starship.
Oh and last time I checked most "nautical vessels" still needed food and water.
That's why they carry food stores. Military vessels are equipped to operate with cut supply lines for months at a time. Granted, military vessels usually purify the water around them for drinking, but a space craft could get away with recycling and excess water stores.
Oh and lets also not forget all of those wonderful "submarine accidents". You kinda failed to mention them, eh?
You mean as opposed to all those space accidents? You kinda failed to mention them, eh?
Never mind that PC's have been saying this since 1982, for the exact same reason: You put an invalid or non-system (floppy) disk in the drive.
You do realize that error is the same one you get when a hard drive goes bad? Sure, I should have considered the floppy, but:
1. It was the weekend and my mind was elsewhere.
2. This was one of those laptops that swap the floppy and the cdrom drive. For some unfathomable reason, they had actually stuck the floppy drive in the laptop and used a floppy disk. Considering that no one does that anymore (even then) it just didn't hit me that they might have had a disk in the drive. At the back of my mind, I kept thinking that there was a cdrom drive installed.
So complain all you want, but you can only diagnose a problem over the phone if you have a proper picture in your mind. Otherwise it would end up taking longer over the phone than driving there, ejecting the floppy, and driving back. (Total time: about 1 hour.)
I hate to break it to you, but that's how free speech works. There's no constitutional protection for anonymity. If you want to be anonymous, you're going to have to do it on someone else's authority. (i.e. Someone who would be willing to protect your identity despite becoming a target himself.)
And before anyone says you'd never be put to death because of domiain information, realize that treason is a capital offense.
Two words: Public Outrage
That's why it's so important not to allow secret trials. And for the most part, judges are pretty good at keeping things on the up and up (no matter what the FBI or CIA wants).
...like it's a big deal. This is the type of law that would only get enforced when you really piss someone off. If you're running an illegal site, you can expect that they'll heap this charge on with the 1000 others they levy against you. Without a motive like illegal activity, it's difficult to prove that you were being intentionally misleading. (Unless you're dumb enough to fill it out with "Snoopy, 10 Charlie Brown Drive, Gotham City" that is...)
Actually, the disk gave the message about a bad disk. i.e. "Invalid or non-system disk."
:-)
That's why it sucked so much. It sounded like a failed hard drive, which was unlikely since the laptop was new. Although the look on her face when I ejected the disk was almost worth the trip.
You mean, like their computer won't boot because they left a floppy in the drive? (Had to drive 20 miles to work on a weekend once, because someone had a big presentation to give. Stupid floppies.)
Of course, Kerry's specifically mentioned his opposition to outsourcing in the past...
That's not necessarily a point in his favor. The question is what he wants to do about it. If solution is to close off our borders and make us internationally unfriendly, then it's a point against him. We need a measured response to problems, not a "cut it off at the knees" response.
How do you do that if you don't know what time it is?
Cripes. The sun rises in the east and sets in the west. If you know if it's morning or afternoon (not tough) you can look to the direction of the sun. Follow the rest of the instructions from there.
Dean, Edwards, Clarks and Liebermans platforms are "Hey! We're not Bush either!"
But Kerry has something they don't: charisma
Oh, and somehow the term "Hitler" gets thrown out when talking about him. The way I figure it, he's already lost the presidency. He's got no platform, and he's already invoked Godwin's law. Not a great situation to find yourself in.
I was referring to the aerodynamics of the rocket. The 75,000 pounder already had the fluid dynamics worked out. Otherwise it wouldn't have been firing for a half-hour.
The Party has annointed him so Vote.A vote for anyone else in your primary or caucus is a vote for Hitle...uh BUSH!
Didn't see this coming. Nope, not at all. Kerry supporters are so non-predictable.
Now, would someone like to tell me what Kerry's platform actually *is*? So far it seems to be, "I'm not Bush, therefore I should be elected." What's his stance on space travel, copyright laws, abortion, education, deficit spending, etc, etc, etc.?! Oh, that's right. "I'm not Bush."
Sure, you can get an approximation by doing that, but the watch method is more accurate (though not as accurate as using a compass).
How can it be more accurate when all you do is point your watch hand in the approximate direction of the sun? It would be much more accurate to take a stick, plunge it upright in the ground, and use it as a sundial. Draw the east-west line of the sun, then cross it with a perpendicular line. The perpendicular line gives you North/South. Now you have exact angles to use for direction. Whenever you fear you're drifting, just stop, repeat, and correct your course.
Now, if someone could just tell me the point of knowing north when you're 100% absolutely lost with no idea what is in what direction...
Or you could just look at the sun, figure out which way is east and west, and by extrapolation figure out north and south. Or is it easier to remember how to turn your watch than which direction the sun rises from?
Enough said - nearly a prototype is not ready for action.
The full scale 250,000 lbs of thrust model was never built. However, the 75,000 lbs of thrust model was built, was tested, and (for a space only vehicle) could be used as is. You'd need either multiple engines or a longer burn to produce the same effect as the 250,000 lb version, but 75,000 lbs at 800 Isp with a 1/2 hour burn is still more than sufficient for a Mars mission.
You just can't say something is ready to fly when you have a scaled down model, if nothing else decades of scramjet development have shown that.
Arguably, a scramjet is far more difficult due to the requirement that it fly in an atmosphere. A NERVA engine for a Mars mission would have no such requirement. As long as the smaller engines could be shown to be space-worthy and reliable, there's no immediate need to scale them up, or even concern ourselves with the difficulties of constructing proper aerodynamics.
I used to work in materials science, working alongside people from a nuclear research facility and the advances haven't been as big as you would think outside of electronic materials. The high temperature and radiation resistant alloys that were in use 30 years ago are still the ones to use. The ceramics developed for the shuttle are still the cutting edge for heat sheilding as well.
And those materials are still way better than the steel and carbons they had in the 1960's. There's also been a lot more research into Plasma containment. Not yet enough to build a "magnetic bottle", but enough to better control the flow and output of the fuel.
It's likely that competing technologies, probably including NERVA will get some funding to see if they will work. Fortunately something of this scale will get enough attention that a good proposal is likely to be chosen, not just a politically expedient one.
NERVA was actually NASA's first choice for a Mars mission back in the 80's. Unfortunately, the public is just as afraid of nuclear technology today as they ever were. If you witnessed the protests over Cassini, then you would probably realize that it will take some gutsy NASA officials to approve a nuclear engine, even solely for space travel.
Still, I hope you're right. Otherwise we'll be stuck with lame ideas like an ION drive final stage, or shipping dozens of solid boosters into an orbital construction yard for use on a Mars mission.
Sorry, try again. You forgot the weight of the mountings, suspension, deployment units, etc. There's more to the solar panels than just the panelling itself. Weight adds up quickly when talking about structure support and reinforcement. (The entire rover weighs 174 Kg.) Motors to deploy the panels are no slouches either, although NASA is probably using a small motor similar to those on an RC car.
BTW, the Rover has a maximum power generating capability of 140 Watts. It takes two batteries to keep the rover running when there isn't enough sunlight. NASA doesn't say what kind of batteries they are (their "specs" on the rover are kind of useless), but external sources claim that they are Lithium Ion batteries with a weight of 7.15Kg a piece (8.77 Kg with the support struts). That same article claims that the rover needs a constant 100 Watts to operate.
Let's do some math shall we?
Design 1: We ditch the batteries all together, and use a 150 Watt RTG. We'll estimate it's weight is ~2Kg of plutonium, plus another 2 Kg of material for the rest of the device and the mountings. The net weight increase is (2 + 2) - (8.77 * 2) = -13.54 Kg.
Design 2: We use a 150 Watt RTG, but keep one battery for high draw situations. The net weight increase is (2 + 2) - 8.77 = -4.77 Kg.
One way or another, it's a win-win situation. Sorry, we're back to the "tree huggers" stopping RTG missions.
I think you're missing the point here. We *have* nuclear engine designs that are *known* to work. The NERVA engines were nearly ready for full scale prototypes before the project was wound down. These engines will give you high thrust (75,000-250,000 lbs.) combined with highly efficient fuel usage (800-1000 Isp). Full scale engines have burned for a full half hour! That's longer than any chemical rocket I'm aware of. Sure, 75,000 pounds of thrust isn't much when compared to a Saturn V, but for a Mars mission, that much power at a longer burn time is the difference between months and years of travel time.
Considering that it would be cheaper to finish development on NERVA than to resurect the Saturn V and improve it's output for a Mars mission, the choice would seem to be obvious. Plus, we have the added benefit of 30 years of materials and nuclear science development. Of course, I'd much rather see GCNR engines, but if you want it done fast, cheap, and effective, NERVA will do it.
Project Pluto. Tested at full power.
NERVA Just about ready to fly. Canned in favor of the Saturn V for moon flights.