I've encountered a few things with respect to ReiserFS:
I get to upgrade my filesystem so that I don't get to downgrade my kernel should I run into trouble.
Whenever something doesn't work right, (which never happened to me on Ext2), Hans Reiser tells me that "it's fixed in the newest version", and I get to upgrade my kernel and on-disk-format without the possiblity to back out.
When things DO go wrong, (which never happend to me on ext2/ext3), it seems I need to tell reiserfsck which sub-version of the filesystem is on my disk (Hans knows that very well on his disks, but I just use filesystems to store my files). Otherwise reiser-fsck may make a bigger mess than it started with.
When reiser-fsck is neccesary, it often requires a "rebuild-tree", which is time-consuming.
My filesystem was "suspect". So I start reiserfsck. It apparently does nothing, as it's done in 2 seconds (which is unlikely on a 640Gb partition) When reiser-fsck --rebuild-tree is started it informs me that it's going to take some 5 hours to complete. As I didn't have that time, I interrupt it. Filesystem gone. Apparently the first thing it does is invalidate the old structures. Now instead of "suspect" I don't have a filesystem at all, and have to sit out the 5 hours for which I don't have the time....
I sometimes have a disk-image of a different filesystem on my disk in a file. Hans Reiser tells me that a rebuild-tree would link the files inside the image into my filesytem! Fixed in newest version. Phew.
Too many (serious) problems, that I'm not ever going to try Reiserfs again. Sorry.
Right. If you have 16 places to vary the plaintext, you only get say 6bits per byte, or about 96 bits of freedom. You'll get "about" 2^96 different md5sums, or have a chance of one in 2^64 of hitting the ONE md5sum that had been signed.
So, you're saying the bank should limit "comment" fields to 16 places, and that will solve the problem?
It is very easy to think of ways to find "bits-of-freedom" in different applications. I reacted to a post where someone found it impossible/unlikely to make a tar.gz's md5sum come out correctly. Give me two seconds and I can come up with a way. 1... 2... You can still adjust the timestamps in the tar.gz for example to give you bits-of-freedom that will allow you to get the signed md5sum.
As an attacker, I might even consider telling gzip not to compress at all. Result: I don't need to reverse the gz step after every adjustment to the next candidate.....
Be careful with "it'll be hard to make this into a real exploit" kind of remarks: the making it into a real attack is easier than cracking the crypto.
For passwords, the collision avoidance of MD5 will make sure that your very complicated password is not "cracked" by some stupid child typing "hi" at your password prompt. But not much more.
The important issue starts when you use PGP to sign your message.
Suppose you sign:
mybank: Please transfer $100 to my son's account: 12345678 ref: Have a nice vacation!
then your PGP program will calculate the MD5 sum of this message and sign that using RSA (or DSA). As all know those algorithms are very very strong.
Next, the attacker will change your message to:
mybank: Please transfer $1000,000 to J. Crook account 87654321 Ref: XXXXXXXXXXXXXXXXXXXXXXXXXXXX
and when the crook can then adjust the XXX part in such a way that an MD5 has collision occurs.... You just authorized your bank to do something you may not have wanted....
There should be about 28 X's in there. That will allow the crook over 2^160 possible messages. Trying them all, there is a high probability that at least one of them has a hash collision with your signed original message. If calculating which one of the possible over 2^160 messages has the "right" MD5sum, costs significantly less than 2^160 operations, then that's considered breaking the hash....
The real news for the initial product seems to be a much faster transfer rate than the current SD format
Not quite: Also the transferrate is an "up to" figure. The write-limit with current flash-media is simply the writing to the chips that is limiting the speed. Even if you have USB2.0 480Mbps transfer medium, will not mean you can write at that speed to something....
A single wire is currently used to transfer say 400Mbps. So you use 128 of them to get 6.4 gB per second of bandwidth to your main memory. (that's beyond the cache!)
If you'd use wireless, and you'd use the 2.4Ghz "band" there is on the order of 2.4Gbits per second of bandwidth. If you stretch it a bit, you'd be able to get about 2.4 Gbytes per second. Use more bandwidth, and you'd be able to get enough for ONE cpu and ONE memory, but no SMP. And you still need your cache.
Now while the first CPU is communicating with it's main memory, you want the second CPU to do the same to a separate memory. Well, they are going to interfere if you don't channel the data trhough those copper guides, commonly called wires....
Note that when you put conductors on a PCB, you get to send more signals just a couple of cm further. But with wireless, you would "spoil" a whole sphere for other uses. Nah. This won't go far.
If you drive, you concentrate on the road, and if you don't do that, you face the consequences when the inevitable happens.
The problem with that is that the authorities have to wait for the inevetable to happen. After passing a "no phoning while driving" law you can use fines to "teach" people that driving and phoning are not compatible.
I've just upgraded my 5-year-old-sony brick to a new nokia. After playing with it for a day, I noticed a feature I missed. In 1 tenth of the formfactor (volume) of my phone, I can get a 256Mb USB memory stick. I want to be able to lug a couple of photos, some MP3s, etc etc on my phone instead of on a separate device. Instead of the puny 1Mb of memory it has now....
With the addition of: If you sort it into a special mailbox, you can quickly walk trhough it with a: "Most if this is spam" attitude. Then if you catch the odd "this shouldn't have been in there, you found someone who misspelled your name. Or you gave out @yourdomain, and they are sending you a legit update. If that happens you can inform the sender in the first case, or add a rule to sort the message differently in the second case.
The fun is to scam the scammer with EXACTLY the same trick as the scammer is using.
The "gain to the world" is that the business of scamming is made less profitable for the scammers. On one side because the baiters use up the time of the scammers by baiting them, on the other hand by scamming them out of some hard-earned....ehmm..... illegally gained dollars.
There are these DVD duplication stations that have a DVD burner and an robotic empty-burning-done mover. you can put a pile of some 50 DVDs on there, so you need to feed it with a new pile of empty DVDs every week or so.
Use a RAID array of 6+1+1 to buffer the data: 6 data disks, one redundancy disk, and 1 hot spare. Remember the hot spare. Your MTBF goes up enormously through the hot spare. Trust me. Or do the math yourself. But please do replace it once one of the disks has failed, and the hot spare has come into action....
Of course, if you require online accesss, then the offline dvds are useless.....
No, not sarcastic. Reportedly true story. If you have > $1M in the bank, you can chose (assuming your legislation allows that) not to spend the $300/month on the health plan.
I'm "digital age". If I want music ("software"), I don't want to have to shove around physical objects, and I don't want to pay for all that shoving that goes on behind the scenes. If I buy the contents of a CD online it's got to cost (cost as in cost to me , but also as in cost to produce) less than what I pay for a CD in a shop. But I'd like to enjoy the same quality as those that bought the physical token. Why not?
Suppose this new system has only one key per disc, coded for a particular private player, using 256-bit Rijndael encryption. It will indeed be uncrackable given only the disc, which is what the quote said.
Assume it's uncrackable, conclude it is uncrackable. Right.
Doing CSS is somthing the hardware of DVD players is cable of. Doing real-time Rijndael is not.
So, I'm guessing they just enter a new decryption key to the player and the disks.
Now, I doubt they have the chance to increase the key size. So if I'm not mistaken, if you put that disk in a Linux machine, I'm afraid it will take up to 60 seconds longer before it will play as libdecss requires that time to brute-force the key......
If you can't afford to save the replacement cost of your essential equipment, maybe it's worth considering whether you could afford it in the first place.
No. If you can't afford to pay for the damage yourself, you need to insure it. I have a house. I insure it as I can't afford to pay for a new one should it burn down. Most people can't afford the open heart surgery. So they get medical insurance. There is this story about a doctor who tells his patient: "You need a bypass. What is your insurance company?" -- "I don't have any." -- "But you're going to die if you don't very bad decision. You can't pay for the $100,000 that open heart surgery costs.". -- "Nope. Very good decision. I've saved well over that $100,000 by not paying the insurance fees, it's waiting in a bankacount for you to send me the bill."
Obaccident. I once did "rm -rf linux" from the/usr/src directory, deleting all my Linux modifications I had done. Ooops. Some of you may remember the old days: minixfs was WAY faster than ext2 in rm-rf of a whole tree. So when I got my prompt back I realized what I had done. Ok. Cool down: two seconds to think about what to do, and then I hit the power switch. One fsck later I had my linux source back. oof.
Are you sure it's the controller chip? It is usually the second largest chip on the fireball. This incident is unrelated to what you were doing. Happens regularly.
In theory, very hard to break. In practice, people severly limit the possible password space to search (how many passwords do you have that have your name, even though you know you shouldn't) so it reduces the amount to passwords you have to try.
The idea (mid seventies) was that one encryption would keep the user waiting at the login prompt for an acceptable 1 second. Checking 100 thousand possible "weak" passwords would be undoable. Computers became faster. A lot. I believe my computer can now do 100 thousand crypts per second. So, now we can not only check the 100 thousand words in the dictionary, but also a whole lot of variations. Like adding a single digit. In short, we can now almost exhaust a much bigger space like "all 8-letter all-lowercase" passwords.
If they are violating Segates patents, then they SHOULD be sued..
The problem is that someone making a modern harddisk and knowing something on how to do things will come up with the same idea. Prior art is something you can prove. But "it's easy for someone skilled in the field" is not.
A patent is an invention that is new (i.e. no prior art), and not obvious to someone skilled in the field. At least that's how dutch and european laws formulate things.
Suppose you're a webshop designer. In your logs you notice that 20% of the clients build up a shopping cart and then don't finish check out. You simplify the shopping process, right? What does this lead to? One click shopping! That is just one example where "someone skilled in the field" will come up with exactly the same idea.
Patents are intended to protect two types of inventions: The ones done in the garage, where the inventor needs some slack to gather funds, build a factory that makes the product, and then market that product and build a market share.
The other type is that where a big investment in time and money is done to develop something. In that case the company that did this investment needs time to recoup their investment.
We're talking about the second case here. Now I seriously doubt that Seagate invested big bucks to come up with ideas that are really innovative so that someone skilled in the field won't come up with them given the same problem.
The sheer amount of patents listed on a seagate harddisk makes it unlikely that they are all really innovating enough to be really patentworthy.
Do you really think that Cornice opened up a seagate harddisk and copied the patented features? I seriously doubt it. They probably came up with most of the 9 patent infringements themselves which proves that: "someone skilled in the fied" would come up with the same solution.
The reason Maxtor isn't sued is because seagate knows that Maxtor has a similar arsenal of patents that they are infringing. So either they have or will have (*) a deal where each promises not to bother the other about patents.
Roger.
(*) The first time one of them sends a letter to the other stating: "You're violating one of our patents, let's talk", the other will send back: "You're violating 10 of our patents. Indeed, let's talk". End result: they agree not to mention the subject again, without any money going either way.
So to get into orbit at 100km above the earth you need about 27MJ/kg of kinetic energy and 1MJ/kg of potential energy. Add them together and you get 28MJ/kg. Note that for the 1MJ/kg I rouded 9.8 m/s^2 to 10. This was NOT your average physics-exam-question, where you're supposed to get the exact answer to the question.
This is a back-of-the-envelope calculation. It shows the order of magnitude of the kinetic and potential energies required to reach orbit.
Now surely, a milestone has been reached. However, handling 10 times more energy to reach almost enough speed to go into orbit is going to be tricky. Even with this milstone behind us. Handling 10 times more energy on reentry is ALSO going to be tricky. Anybody remember what did columbia in? It's the massive amount of energy involved in being in orbit. It would be nice if you'd be able to take a long time in coming back so that this energy can be disspated slowly. However, once you hit the atmosphere, you start to slow down, and you start to fall. No two ways about it. So it's a problem. Needs to be solved. Ceramic tiles on the bottom of the space-shuttle work so-so.
But back of the envelope says it's not 10 times, it's about 27 times. Could be 20 times. Could be 35 times. I don't care. It clearly shows: "we're not there yet".
(If the back-of-the envelope calculation would show say 1MJ/kg of kinetic energy, and 27MJ/kg of potential energy, then the energy argument cannot be used to say: we're not quite there yet. In fact, then I'd actually think that it's minor problems to actually go into orbit. But over 20 times more energy means significant scaling-problems....)
Completely right. But engineering is about knowing when you can neglect certain quantities.
The earth's radius is something like 6000km. Adding 100km adds in 1.7%, due to the quadratic relation, that would mean a decrease in gravity of about 3.4%, so if you want to do more accurate math, feel free to correct my calculations by less than 5%.
Orbital speed is not constant. But in low-earth-orbit (like space shuttle), the fact that you're an insignificant amount further than the radius of the earth, means that they are all about 90 minutes. If you go from 100km to 200km above the earth the speed goes down something like 1.7%. Again, for an order of magnitude calculation completely insignificant.
To get to 100km height, you need m * g * h in energy. per unit of mass you get: g * h = 9.8 * 100 *10^3 ~=~ 1 MJ/kg.
In orbit, you'll circle the earth every 1.5 hours. That means a speed of about 7.4km/sec. This requires (again per unit of mass) 1/2 * v^2 = 0.5*7400^2= 27 MJ/kg.
So, reaching (low earth-) orbit requires about 27 times more energy than what was demonstrated now.
Now there are a few things to keep in mind. You'll have to lug along the fuel to accelrate the last part of your ascent. That means that just taking 27 times more fuel won't cut it.
We're at least two orders of magnitude away from commercial manned spaceflight. (where spaceflight is defined as "in orbit"). Sure: Big step, but not quite there yet....
Start your calculation with the number of Gb of space you "need". Say that this is 160Gb. Then you have the option of: L0: no raid: 1x 160Gb or 2x80 L1: raid1: 2x 160Gb. L1: raid5 (3 disks): 3x80Gb. L1: raid5 (4 disks): 4x60Gb L1: raid5 (5 disks): 5x40Gb and you could even go for a hot spare: L2: raid5HS (4 disks): 4x80Gb. L2: raid5HS (5 disks): 5x60Gb L2: raid5HS (6 disks): 6x40Gb
Now, from 4 disks you probably need an extra IDE controller in your computer. Factor that into your costs, and you can chose the protection level (L0 means you can tolerate 0 lost disks. L2 means 2 disks, but in fact not at exactly the same time, but you can tolerate two bad disks).
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- I get to upgrade my filesystem so that I don't get to downgrade my kernel should I run into trouble.
- Whenever something doesn't work right, (which never happened to me on Ext2), Hans Reiser tells me that "it's fixed in the newest version", and I get to upgrade my kernel and on-disk-format without the possiblity to back out.
- When things DO go wrong, (which never happend to me on ext2/ext3), it seems I need to tell reiserfsck which sub-version of the filesystem is on my disk (Hans knows that very well on his disks, but I just use filesystems to store my files). Otherwise reiser-fsck may make a bigger mess than it started with.
- When reiser-fsck is neccesary, it often requires a "rebuild-tree", which is time-consuming.
- My filesystem was "suspect". So I start reiserfsck. It apparently does nothing, as it's done in 2 seconds (which is unlikely on a 640Gb partition) When reiser-fsck --rebuild-tree is started it informs me that it's going to take some 5 hours to complete. As I didn't have that time, I interrupt it. Filesystem gone. Apparently the first thing it does is invalidate the old structures. Now instead of "suspect" I don't have a filesystem at all, and have to sit out the 5 hours for which I don't have the time....
- I sometimes have a disk-image of a different filesystem on my disk in a file. Hans Reiser tells me that a rebuild-tree would link the files inside the image into my filesytem! Fixed in newest version. Phew.
Too many (serious) problems, that I'm not ever going to try Reiserfs again. Sorry.Right. If you have 16 places to vary the plaintext, you only get say 6bits per byte, or about 96 bits of freedom. You'll get "about" 2^96 different md5sums, or have a chance of one in 2^64 of hitting the ONE md5sum that had been signed.
So, you're saying the bank should limit "comment" fields to 16 places, and that will solve the problem?
It is very easy to think of ways to find "bits-of-freedom" in different applications. I reacted to a post where someone found it impossible/unlikely to make a tar.gz's md5sum come out correctly. Give me two seconds and I can come up with a way. 1... 2... You can still adjust the timestamps in the tar.gz for example to give you bits-of-freedom that will allow you to get the signed md5sum.
As an attacker, I might even consider telling gzip not to compress at all. Result: I don't need to reverse the gz step after every adjustment to the next candidate.....
Be careful with "it'll be hard to make this into a real exploit" kind of remarks: the making it into a real attack is easier than cracking the crypto.
For passwords, the collision avoidance of MD5 will make sure that your very complicated password is not "cracked" by some stupid child typing "hi" at your password prompt. But not much more.
The important issue starts when you use PGP to sign your message.
Suppose you sign:
mybank: Please transfer $100 to my son's account: 12345678 ref: Have a nice vacation!
then your PGP program will calculate the MD5 sum of this message and sign that using RSA (or DSA). As all know those algorithms are very very strong.
Next, the attacker will change your message to:
mybank: Please transfer $1000,000 to J. Crook account 87654321 Ref: XXXXXXXXXXXXXXXXXXXXXXXXXXXX
and when the crook can then adjust the XXX part in such a way that an MD5 has collision occurs.... You just authorized your bank to do something you may not have wanted....
There should be about 28 X's in there. That will allow the crook over 2^160 possible messages. Trying them all, there is a high probability that at least one of them has a hash collision with your signed original message. If calculating which one of the possible over 2^160 messages has the "right" MD5sum, costs significantly less than 2^160 operations, then that's considered breaking the hash....
The real news for the initial product seems to be a much faster transfer rate than the current SD format Not quite: Also the transferrate is an "up to" figure. The write-limit with current flash-media is simply the writing to the chips that is limiting the speed. Even if you have USB2.0 480Mbps transfer medium, will not mean you can write at that speed to something....
A single wire is currently used to transfer say 400Mbps. So you use 128 of them to get 6.4 gB per second of bandwidth to your main memory. (that's beyond the cache!)
If you'd use wireless, and you'd use the 2.4Ghz "band" there is on the order of 2.4Gbits per second of bandwidth. If you stretch it a bit, you'd be able to get about 2.4 Gbytes per second. Use more bandwidth, and you'd be able to get enough for ONE cpu and ONE memory, but no SMP. And you still need your cache.
Now while the first CPU is communicating with it's main memory, you want the second CPU to do the same to a separate memory. Well, they are going to interfere if you don't channel the data trhough those copper guides, commonly called wires....
Note that when you put conductors on a PCB, you get to send more signals just a couple of cm further. But with wireless, you would "spoil" a whole sphere for other uses. Nah. This won't go far.
Insert chips from other side?
The problem with that is that the authorities have to wait for the inevetable to happen. After passing a "no phoning while driving" law you can use fines to "teach" people that driving and phoning are not compatible.
I've just upgraded my 5-year-old-sony brick to a new nokia. After playing with it for a day, I noticed a feature I missed. In 1 tenth of the formfactor (volume) of my phone, I can get a 256Mb USB memory stick. I want to be able to lug a couple of photos, some MP3s, etc etc on my phone instead of on a separate device. Instead of the puny 1Mb of memory it has now....
With the addition of: If you sort it into a special mailbox, you can quickly walk trhough it with a: "Most if this is spam" attitude. Then if you catch the odd "this shouldn't have been in there, you found someone who misspelled your name. Or you gave out @yourdomain, and they are sending you a legit update. If that happens you can inform the sender in the first case, or add a rule to sort the message differently in the second case.
I add a couple of extra spamassassin points to Emails that are not addressed to one of my published addresses.
So he took a risk. His risk. His choice.
....ehmm..... illegally gained dollars.
The fun is to scam the scammer with EXACTLY the same trick as the scammer is using.
The "gain to the world" is that the business of scamming is made less profitable for the scammers. On one side because the baiters use up the time of the scammers by baiting them, on the other hand by scamming them out of some hard-earned
There are these DVD duplication stations that have a DVD burner and an robotic empty-burning-done mover. you can put a pile of some 50 DVDs on there, so you need to feed it with a new pile of empty DVDs every week or so.
Use a RAID array of 6+1+1 to buffer the data: 6 data disks, one redundancy disk, and 1 hot spare. Remember the hot spare. Your MTBF goes up enormously through the hot spare. Trust me. Or do the math yourself. But please do replace it once one of the disks has failed, and the hot spare has come into action....
Of course, if you require online accesss, then the offline dvds are useless.....
No, not sarcastic. Reportedly true story. If you have > $1M in the bank, you can chose (assuming your legislation allows that) not to spend the $300/month on the health plan.
I'm "digital age". If I want music ("software"), I don't want to have to shove around physical objects, and I don't want to pay for all that shoving that goes on behind the scenes. If I buy the contents of a CD online it's got to cost (cost as in cost to me , but also as in cost to produce) less than what I pay for a CD in a shop. But I'd like to enjoy the same quality as those that bought the physical token. Why not?
That's what they did last year. IIRC the traced perpretator claimed his son stole/copied the DVD....
Suppose this new system has only one key per disc, coded for a particular private player, using 256-bit Rijndael encryption. It will indeed be uncrackable given only the disc, which is what the quote said.
Assume it's uncrackable, conclude it is uncrackable. Right.
Doing CSS is somthing the hardware of DVD players is cable of. Doing real-time Rijndael is not.
So, I'm guessing they just enter a new decryption key to the player and the disks.
Now, I doubt they have the chance to increase the key size. So if I'm not mistaken, if you put that disk in a Linux machine, I'm afraid it will take up to 60 seconds longer before it will play as libdecss requires that time to brute-force the key......
If you can't afford to save the replacement cost of your essential equipment, maybe it's worth considering whether you could afford it in the first place.
/usr/src directory, deleting all my Linux modifications I had done. Ooops. Some of you may remember the old days: minixfs was WAY faster than ext2 in rm-rf of a whole tree. So when I got my prompt back I realized what I had done. Ok. Cool down: two seconds to think about what to do, and then I hit the power switch. One fsck later I had my linux source back. oof.
No. If you can't afford to pay for the damage yourself, you need to insure it. I have a house. I insure it as I can't afford to pay for a new one should it burn down. Most people can't afford the open heart surgery. So they get medical insurance. There is this story about a doctor who tells his patient: "You need a bypass. What is your insurance company?" -- "I don't have any." -- "But you're going to die if you don't very bad decision. You can't pay for the $100,000 that open heart surgery costs.". -- "Nope. Very good decision. I've saved well over that $100,000 by not paying the insurance fees, it's waiting in a bankacount for you to send me the bill."
Obaccident. I once did "rm -rf linux" from the
Are you sure it's the controller chip? It is usually the second largest chip on the fireball. This incident is unrelated to what you were doing. Happens regularly.
In theory, very hard to break. In practice, people severly limit the possible password space to search (how many passwords do you have that have your name, even though you know you shouldn't) so it reduces the amount to passwords you have to try.
The idea (mid seventies) was that one encryption would keep the user waiting at the login prompt for an acceptable 1 second. Checking 100 thousand possible "weak" passwords would be undoable. Computers became faster. A lot. I believe my computer can now do 100 thousand crypts per second. So, now we can not only check the 100 thousand words in the dictionary, but also a whole lot of variations. Like adding a single digit. In short, we can now almost exhaust a much bigger space like "all 8-letter all-lowercase" passwords.
If they are violating Segates patents, then they SHOULD be sued..
The problem is that someone making a modern harddisk and knowing something on how to do things will come up with the same idea. Prior art is something you can prove. But "it's easy for someone skilled in the field" is not.
A patent is an invention that is new (i.e. no prior art), and not obvious to someone skilled in the field. At least that's how dutch and european laws formulate things.
Suppose you're a webshop designer. In your logs you notice that 20% of the clients build up a shopping cart and then don't finish check out. You simplify the shopping process, right? What does this lead to? One click shopping! That is just one example where "someone skilled in the field" will come up with exactly the same idea.
Patents are intended to protect two types of inventions: The ones done in the garage, where the inventor needs some slack to gather funds, build a factory that makes the product, and then market that product and build a market share.
The other type is that where a big investment in time and money is done to develop something. In that case the company that did this investment needs time to recoup their investment.
We're talking about the second case here. Now I seriously doubt that Seagate invested big bucks to come up with ideas that are really innovative so that someone skilled in the field won't come up with them given the same problem.
The sheer amount of patents listed on a seagate harddisk makes it unlikely that they are all really innovating enough to be really patentworthy.
Do you really think that Cornice opened up a seagate harddisk and copied the patented features? I seriously doubt it. They probably came up with most of the 9 patent infringements themselves which proves that: "someone skilled in the fied" would come up with the same solution.
The reason Maxtor isn't sued is because seagate knows that Maxtor has a similar arsenal of patents that they are infringing. So either they have or will have (*) a deal where each promises not to bother the other about patents.
Roger.
(*) The first time one of them sends a letter to the other stating: "You're violating one of our patents, let's talk", the other will send back: "You're violating 10 of our patents. Indeed, let's talk". End result: they agree not to mention the subject again, without any money going either way.
The first civillan died on challenger. All others who went into space were officially in the miltary. Really.
Completely right.
So to get into orbit at 100km above the earth you need about 27MJ/kg of kinetic energy and 1MJ/kg of potential energy. Add them together and you get 28MJ/kg. Note that for the 1MJ/kg I rouded 9.8 m/s^2 to 10. This was NOT your average physics-exam-question, where you're supposed to get the exact answer to the question.
This is a back-of-the-envelope calculation. It shows the order of magnitude of the kinetic and potential energies required to reach orbit.
Now surely, a milestone has been reached. However, handling 10 times more energy to reach almost enough speed to go into orbit is going to be tricky. Even with this milstone behind us. Handling 10 times more energy on reentry is ALSO going to be tricky. Anybody remember what did columbia in? It's the massive amount of energy involved in being in orbit. It would be nice if you'd be able to take a long time in coming back so that this energy can be disspated slowly. However, once you hit the atmosphere, you start to slow down, and you start to fall. No two ways about it. So it's a problem. Needs to be solved. Ceramic tiles on the bottom of the space-shuttle work so-so.
But back of the envelope says it's not 10 times, it's about 27 times. Could be 20 times. Could be 35 times. I don't care. It clearly shows: "we're not there yet".
(If the back-of-the envelope calculation would show say 1MJ/kg of kinetic energy, and 27MJ/kg of potential energy, then the energy argument cannot be used to say: we're not quite there yet. In fact, then I'd actually think that it's minor problems to actually go into orbit. But over 20 times more energy means significant scaling-problems....)
Completely right. But engineering is about knowing when you can neglect certain quantities.
The earth's radius is something like 6000km. Adding 100km adds in 1.7%, due to the quadratic relation, that would mean a decrease in gravity of about 3.4%, so if you want to do more accurate math, feel free to correct my calculations by less than 5%.
Orbital speed is not constant. But in low-earth-orbit (like space shuttle), the fact that you're an insignificant amount further than the radius of the earth, means that they are all about 90 minutes. If you go from 100km to 200km above the earth the speed goes down something like 1.7%. Again, for an order of magnitude calculation completely insignificant.
To get to 100km height, you need m * g * h in energy. per unit of mass you get: g * h = 9.8 * 100 *10^3 ~=~ 1 MJ /kg.
In orbit, you'll circle the earth every 1.5 hours. That means a speed of about 7.4km/sec. This requires (again per unit of mass) 1/2 * v^2 = 0.5*7400^2= 27 MJ/kg.
So, reaching (low earth-) orbit requires about 27 times more energy than what was demonstrated now.
Now there are a few things to keep in mind. You'll have to lug along the fuel to accelrate the last part of your ascent. That means that just taking 27 times more fuel won't cut it.
We're at least two orders of magnitude away from commercial manned spaceflight. (where spaceflight is defined as "in orbit"). Sure: Big step, but not quite there yet....
Start your calculation with the number of Gb of space you "need". Say that this is 160Gb. Then you have the option of:
L0: no raid: 1x 160Gb or 2x80
L1: raid1: 2x 160Gb.
L1: raid5 (3 disks): 3x80Gb.
L1: raid5 (4 disks): 4x60Gb
L1: raid5 (5 disks): 5x40Gb
and you could even go for a hot spare:
L2: raid5HS (4 disks): 4x80Gb.
L2: raid5HS (5 disks): 5x60Gb
L2: raid5HS (6 disks): 6x40Gb
Now, from 4 disks you probably need an extra IDE controller in your computer. Factor that into your costs, and you can chose the protection level (L0 means you can tolerate 0 lost disks. L2 means 2 disks, but in fact not at exactly the same time, but you can tolerate two bad disks).
Then simply chose the cheapest solution.
I'd probably go for 3x80 myself.