pa1983

I have not been playing KSP a lot the last few years after I quit building space planes. Was a bit hard to find something fun to do motivating me to play but eventually I decided to use KOS and do some scripting. I cant code or script realy so that was interesting After doing some scripts that could take a specific rocket up in orbit or a spaceplane up and land I decided I needed something "Universal". Even with a handful of scripts and rockets when I played career with limited parts one have to invent rockets as the parts are unlocked so realy my new shiny rockets and there scripts where useless until the "end game". So I needed something that worked with most rockets. That is when I started to work on my "Universal Rocket Launch System" or URLS as I like to call it. Its written for KSP 1.2.2 and KOS, I suppose never versions "should work"? You can download the script here. https://dl.dropboxusercontent.com/u/27196441/urls.zip The goal with the scrip is to put ANY payload in a 100-103km Low Kerbal Orbit. Now Im no programmer or scripted, And Im definitely not good at maths so my "formulas" might be a bit strange but they get the job done at least tough there not always as precise as I would like them to be. The script consist of a number of guidance modes. But basically the rockets pitch is calculated and set based on its altitude using a formula I created. The rockets velocity is calculated based of altitude to using a formula I derived and the engines are throttled accordingly to maintain proper acceleration trough the gravity turn. I actually derived my gravity turn formula used for the pitch with a rocket I called the Delta I. It could naturally do a gravity turn so I recorded that data, created a simple script that mimicked that and also tuned the thrust of the stages accordingly. Once I had this simple script I had enough data to create the gravity turn formula I mentioned earlier and the formula for the target velocity and all other formulas I needed. Now the problem is that not every rocket behaves like the one I used as a benchmark, the Delta I. The most common problem I noticed was either a to powerful first stage and a weak second stage and this created a problem. If the second stage is to weak aka low TWR it will not gain altitude fast enough, basically it will fall short of the intended profile of the gravity turn. Since the velocity is calculated based on altitude a second or 3:e stage could actually find it self costing at a pitch up attitude and just run out of fuel since the script did not demand full thrust because the orbital speed at that altitude was meet. As fare as the script was concerned the orbital velocity at that altitude was correct and sure it was but since vertical velocity was around zero the stage would just cost until the fuel ran out. So my next guidance mode I had to create is also based of altitude BUT the formula I derived calculates what time the rocket should be at that altitude. If we assume the rocket turns as programmed by she script and accelerates properly we should always know at what time our rocket should be at a specific altitude. So this secondary guidance mode basically calculates the time the rocket should be at Altitude X and it checks that against the time since launch and if we are ahead or behind to much this guidance mode takes control over the throttle. This mode wont allow the velocity of the rocket to go below 90% of the velocity that was the target, simple reason is that we dont want the rocket to fall out of the sky but other then that it can override the velocity as much as desired to "catch up". This secondary guidance mode will allow even a second or 3:e stage to coast in to orbit. Usually when the second or 3:e stage struggles to get in to orbit its usually enough just to move fuel from that stage to the previous stage, that gives more D/V on previous stage and a lighter second or 3:e stage giving them better TWR. The last guidance mode is basically there to put the rocket in LKO and this mode is activated either when the AP is deemed high enough or the rocket is high enough in orbit. To be able to understand what the script is doing I created a User Interface. It will show useful data the script uses and what guidance modes are in use and what part of the script has completed. This is very useful when designing a rocket to fly with the script. One can pretty easily determine if a stage has the proper TWR or not for example or adjust thrust limits on solid rocket boosters for example since the script has no control over those. I will now explain what the screen shows from top to bottom Apoapsis altitude - this is just apopasis altitude in meters so pretty strait forward Periapsis altitude - this is your periapsis altitude in meters. Vertical speed - this is your rockets vertical speed in m/s so useful to tune thruster limits and engine configurations. Vertical speed target - this is the vertical speed in m/s your rock should travel at the first 1000m after launch. Orbital Velocity - this is the orbital velocity in m/s of your rocket and its used for simplicity from launch to LKO. Velocity deviation - this shows the difference between the calculated velocity and the actual velocity in m/s the rocket is travelling at. Positive number and the rocket is going to fast and a negative number and the rocket is going to slow. Time in flight - this is the time the rocket has been flying since launch shown in seconds only. Deviation from ideal trajectory - this will show you how much behind or ahead in time in seconds the rocket is on its trajectory, ideally you want no deviation but some will eventually occur as the rockets vertical speed declines the accuracy is reduced. Target pitch - this shows the pitch the rocket is suppose to have not what it is, apparently it was very "hard" to script something that would show the rockets actual pitch so you should check this pitch value against the navball to make sure your rocket actually has the authority to pitch over as demanded. Then we have guidance modes. Only one guidance mode can have full authority at a time and what mode has authority will be shown with the word "Active" next to it. Vertical Velocity - This guidance mode is used the first 1000m of the accent, the rocket tries to go strait up and accelerate at a predetermined rate. Orbital Velocity - This is the primary guidance mode for the gravity turn and the one you want to spend most of the time in. It controls the velocity of the rocket according to altitude and should work for any rocket with good enough TWR. Time deviation - this is the secondary or fallback guidance mode. Its primary job is to take control from "Orbital Velocity" guidance mode if the rocket for example has an excessive TWR, like solid rocket boosters that was not properly configured with a thrust limit. Its more commonly activated when a second or 3:e stage has a to low TWR and it will make sure full throttle is used to try and coast the rocket in to orbit. I have also had instances where boosters smashed one of my main engines of and then this mode could save the rocket to. You dont realy want to be in this mode because then your rocket is not balanced to work well with the script but since this guidance mode is based on altitude it will be less accurate at say 50km or higher since the vertical speed decreases and the rockets starts to level of so even the best rockets might spend 10-20 sec in this mode before going in to the last guidance mode. This mode is also triggered if the rocket is 5 seconds behind or ahead of its intended point in time. Orbital Manoeuvrers - this is the last guidance mode and its basically there to get your in to LKO. It is activated either when the rocket has high enough altitude or when the AP is high enough. We dont want the AP to go higher then the intended LKO do we. The last part in our User Interface is Mission parameters. The word complete will be shown next to a mission parameter when it has been executed. Gravity turn - gravity turn is completed. LKO - rocket is in a stable Low Kerbal Orbit. Payload delivery - payload has be deployed. Deorbit burn - the orbital stage has done a retro burn and will now reenter Kerbin at 30km altitude and burn up. Now there area few other things that needs to be mentioned about the script. If an attribute in the User Interface reads "null" the that only means the data is no longer correct or available and therefore no data is shown to confuse the user. The script will check for engine flameouts and will stage as long as there are flamed out engines. The script will also check for active engines and stage until active engines are detected. Every time the rocket stage it will default to full thrust on the engines just to make sure it wont fall behind on its intended trajectory since the TWR will usually be lower with a new stage then an empty one. The scrip uses action group 10 to jettison faring or anything else you want to get rid of, this will happen at 54000m. If you want to jettison your faring earlier you can have that in your staging sequence as usual. The reason I opted for 54000m to jettison fairings is the the fact that I got destructive wobble with 3.75m parts up to about 50000m. Since the script is universal I need a safe altitude to deploy the fairings. The script will stage one last time in orbit to jettison then payload, but action group 9 is also triggered and can be used to separate a payload from the last stage and also extend antennas if you need an uplink to control the payload. Also the scripts formula to estimate velocity is a bit off in the early part of the gravity turn compared to the rocket it was designed for (Delta I) so its pretty common for it to report that the rocket is a bit behind in velocity but still show that the rocket is on time aka no Time Deviation. Try out the Delta II rocket supplied with the script for a good benchmark rocket to use as a reference. For the first stage I usually use a TWR of 1.5 based of the Vacuum numbers, if I use the atmospheric numbers I tend to go with 1.3. The scrip is primarily intended to make launches easy and routine and not to make them the most efficient to save that little bit of fuel. You should tune your rocket so it spends most time in the "orbital velocity" guidance mode for best performance but the script is intended to fly pretty much anything that can be flown manually tough its not designed for space shuttles. I have tested pretty much all my rockets, good and bad once and also most stock rockets in KSP and they do work (staging order might need tuning tough). You can download the script here. https://dl.dropboxusercontent.com/u/27196441/urls.zip It will include the Delta II rocket (improved version of the Delta I but performance the same) and also a Soyuz ST (picture below) that I designed using the script. I would recommend flying them first to get an idea of how the script works and how you can use it to tune your rockets. So now its up to you to break my script and tell me what it cant do So feel free to post any good or bad launches in this thread.

Firmware patch is coming the 15th October at the earliest samsung sees. http://www.nordichardware.se/SSD/HDD/prestandaproblemen-i-samsung-840-och-840-evo-korrigeras-i-firmware-uppdatering.html http://www.golem.de/news/samsung-ssd-firmware-fuer-840-evo-gegen-tempoverlust-kommt-mitte-oktober-1409-109434.html http://www.sweclockers.com/nyhet/19375-samsung-lovar-atgarda-prestandaproblem-i-840-serien-ssd-med-ny-firmware

No samsung realy wants to keep a lid on things as much as they can. Never samsung again for that reason. Customer support is just terible. It was good before I think. When I got a bad LCD monitor 5 years ago or something they sent a brand new one out ASAP after a phone call. But the new 3:e party support that dont have any contact with samsung just sucks so much. The retailers I spoken with confirms that the end user has no chance realy with there support nowdays. They are to big on retailer told me. The fact that people like me and hundred of others have made us heard eventually triggered tech sites to write about it. Nordichardware thanked me for the brining it up and helping them best I could collecting more data for there article. But it sad that it took almost 2 months before samsung responded to the uproar from frustrated users. Never Samsung Again! Sweclockers responded to one of my e-mails but never none of the later once with anandtechs article etc. But they wrote an article finally about it. its like 200K swedish users in there forum so. Any news there gets attention. http://www.sweclockers.com/nyhet/19362-samsung-840-och-840-evo-ssd-lider-av-prestandaproblem

Nordichardware.se wrote an article. Have have had email contact with them the past two weeks. Its in swedish but google translate should work. http://www.nordichardware.se/SSD-Recensioner/sa-kringar-du-prestandaproblemen-i-samsung-840-och-840-evo.html

Samsung acknowledges the problem and is working on a firmware fix. No ETA but this is progress. At least they can be held responsible now sense they admit to the problem. http://www.anandtech.com/show/8550/samsung-acknowledges-the-ssd-840-evo-read-performance-bug-fix-is-on-the-way

Well I ended up ordering replacement Crucial MX100 for all effected systems I built. Anandtechs wrote in there comments to the new sandisk SLC drive that they have information they will reveal in a few days about the 840 /840 EVO bug so I would stay tunned to that web page the next few days and see what happens.

Yes its good to show other models are not effected.

830 and 840PRO uses MLC NAND and are not effected as fare as we know.

Yea for now. Sadly wont last forever. interesting to see another 840 effected tough since the 840 EVO gets the most attention.

Well only a fraction of users would know about the problem and fewer would user a fix. In the end I dont think its viable option. I will clam manufacturer fault here in Sweden either its covered by samsung or not here in Sweden any product with a proven manufacturing fault you can send back for a replacement. And if they cant fix it well then they have to refund you. And I already spoken with one of my resellers and with the amount off evidence it should not be a issue they told me. All they wanted are links to threads to confirm that more people are effected then by law they are obligated to help me. And if samsung wont release a fix I can skip the howl replacement product step the law allows the reseller to take if its a possibility. Theres no way a reseller can fix a broken SSD.

Yes people tested that. People that wants to know more should read trough the overclock.net thread. They are implementing such fuctions in those test programs to do just that. But rewriting data restores performance. So if you have some way of doing that it should work as a temporary fix. But expect the problem to return in a few months. This is also the reason I think Samsung could make a fix like that part of ware leveling. Either move data after X amount of time or do a read the of LBA's sequentially at idle and rewrite any slow data. If the degradation happens after average 2 months that would mean it cost you 6 PE cycles per cell a year assuming the cells have data stored so a small fraction of the 1000 PE cycles per cell would be used every year.

As fare as I have seen the degradation ONLY happens in cells containing data so yea you wont see this on a new or unused 840 or 840 EVO. So where the SSD is fast is where it has not stored data or stored data recently. Windows users can use this program on there own risk. It will read actuall files and tell you how fast they read and how old they are. A user wrote it over at overclockers.net so us it on your own risk. I used it on the 840 500GB with no problems tough. https://dl.dropboxusercontent.com/u/27196441/840/SSDReadSpeedTester1.00.zip Results will look something like this if your files reads slower the older they are. Linux users can use this script. https://dl.dropboxusercontent.com/u/27196441/840/SSD840bench.sh Just add the dir after the script you wish to test. Root is not required. If your drive is effected the best forum so fare seems to be over at overclockers.net. Link to the thread is in my first post. Registering is easy there. The UK forum denied my registration. Probably because its connected to a store and they want UK users only. The sad thing is that pretty much every one that has tested there drives after being informed of the issue have had the fault. I have seen users that tested multiple 840 EVO being so sure the next on they test will have it they are willing to bet there lives on it more or less. So the issue seems to effect every TLC samsung model so fare with very few exceptions. New drives usually dont showt he problem until 2-3 months with static data on the.

I also know its less durable etc. Its not realy the users concern if Samsung messed up the reliability of TLC NAND if the user celected a SSD that has a life span that fits the users needs. On all our systems we will never hit the advertised write limit. Also only one system can fully exploit the performance due to sata 6Gbit, the rest are stuck on 3Gbit and are basically boot drives for Linux and some basic services. Back when Gen1 and 2 SSD's where out static life span of data was some times in the specs. if I recall 10 years where not uncommon for SLC and MLC drives back then. The basics of NAND is that SLC uses two voltage states to reprecent 0 an 1. MLC represents it with 4 states to encode 00, 01, 10, 11. TLC needs 8 states to encode 000 to 111. The controller basically programs the cell with a voltage it knows represents a series of bits. Problem is if you try to store 3bits with 8 states in a 3V range the margin is half compared to MLC with 4 states and a 3V range. If I recall teh 840 EVO programs it cells with 15-18V so the 8 states needs to fit in there. So that means the controller need to write very accurate voltage level but also be able to read it back later and determent what bits the voltage represent on the fly. To me the later seems to be the problem. The TLC might just be degrading so fast that ECC has to kick in. If I recall anandtech wrote that TLC used 24bit ECC and MLC 15bit ECC. Couple that with MLC being more proved and should take a lot longer to degrade where it would cause problems for the controller this might explain the slow read performance on 840 EVO afte a few months. Also even if the TLC is at fault a firmware should be able to refresh cells making the Tech more viable. For light use, typical desktop or boot drive even if the TLC drive shuffled the static data around every so often it might cost 6-12 PE cycles on a 100% full drive etch year. Not a big cost I say with 1000 PE cycles. From my small sample size and from what I see the 840 seems to degrade slower so I suspect the 21nm TLC NAND dont degrade as fast as the 19nm NAND in the EVO but thats just speculations. Need more drives to be sure of that. My 840 only degrades to EVO speeds after 11 months instead of 3 months so. That theory would to some part explain why we only see 840 owners reporting the fault at a limited number unlike 840 EVO owners and also why 840 owners reports it now and not before to a bigger extent. I my self is no fan of TLC BUT Samsung good reputation, Sandforce 2 bad reputation, OCZ being junk the 840 and 840 EVO seemed like good enough for many people and the reviews where good to. In my primary rig I run a MLC Crucial M4 SSD. Also in my HTPC i use an Intel 320. But if it was not for this degradation of the read speed on the 840 and 840 EVO I cant see what use MLC or SLC would do in a system that makes very few writes a year and hardly requires the performance of high end SSD's. SSD for me in my router and NAS is just to keep noise down, power use and save space instead of having an old HDD hosting the OS. The cost between a low end SSD and a low end HDD is not that big.

I know the differens between SLC, MLC and TLC. NAND. In practice its just a question of the number of voltage states used during programing. The 840 EVI uses15-18V to reprisent 8 states, 3bits. But the 840 EVO also uses the TLC NAND in SLC mode for faster writes called torbowrite. Just uses some dedicated TLC NAND for that. The MX100 is considered better since it has MLC NAND. But NAND is NAND, not realy that much of a difference. Problem is that the more bits you reprecent the smaller the margines on the voltage used for programing. NAND cant keep data for ever ither. What samsung saves is not cost per chip but they can use fewer chips for the same amount of storage. The 840 500GB has less then 300h on it after 1.5 years. Used for surfing and storing photos. At the time 500GB MLC was way to much and even TLC whit less PE cycles would last longer then the machine. So no reason for a expensive MLC SSD at the time. My linux router uses the EVO, it sees 10-100MB written to it a day I would say. I could never use all the PE cycles even on a TLC SSD.

Well due to the nature of how SSD's works you might not notice it at first. An SSD even at 50MB/sec and access times in the low 0.2ms will still feel faster then a hard drive especially at random access. But people have noticed slow downs in daily use. Depends very much on how heavy your use scenario is. People that do daily backups have noticed a big increase in time it takes for the scheduled backup to complete. Any way I hop the information was helpful to some one.

Yes but the thread is mainly to inform people that are unaware of the problem and might be effected. If they are member in any of the forums mentioned I assume they will go there. And even if they are not a member the information migth help them in a RMA case if thats the route they want to take. Yes seems to be a popular alternative and cheaper even.

If I read the forum description properly this topic should be allowed I think. I would assume there are plenty of people here that might own an Samsung 840 or 840 EVO that might find it useful. Im also posting in hardware forums, more then one to be exact. This is the first on this topic I created just to make people aware of the issue not to cause trouble. And I would like post to be on the topic, perfectly fine to ask questions but the problem exist and is not the fault of the users.

So this tech site Article is laying then with the hundreds of use reporting the problem? http://www.3dnews.ru/901747 Or another well known forum and tech site discusses the problem. http://linustechtips.com/main/topic/214537-samsung-840-evo-ssd-performance-degradation/

Read what I wrote and posted. I have used SSD since generation 2 and know very well how they work. Ether read the threads created by other effected users where a lot more effected users have respond whit the same problem so this is FARE beyond user error and control when it comes to a fix. Any one knowledgeable with how SSD's works can concluded that this is a Hardware/firmware issue. Question is what will samsung do about it. I did not create this thread because there is one or two users with the problem but hundreds of reports from users that know they suffer from the same problem and there are fare more that are effected that are not aware of the problem as of yet. Peleny of threads where people have the problems to with out knowing it just by looking at the image dumps of HD tune or HD sentinel. The threads I posted are just the biggest once available for public viewing. I can tell you there are more discussions going on all over the Internet about this. Samsung have taken in 840 EVO's from users to diagnose the problem so its not some minor issue where talking here that the user can fix. A firmware upgrade is a minimum IF that can fix the problem. If its hardware related then a fix might not be possible on existing 840 and 840 EVO. I very good at computer hardware and know perfectly well what sata chipset supports trim or not and what there I/O and bandwidth performance they have. So yes it uses native Intel Sata 6Gbit ports. I have had at least 7 different SSD's and installed more in other systems and none of them behaves like this. Most of my machines run gentoo linux with the discard option and proper partition alignment. The 840 500Gb I showed image dumps is a machine that runs windows 7 premium 64bit.

The past two months people have slowly noticed that there is a problem with the Liner Read performance of Samsung 840 EVO, The 840 have also shown to have the same problem. Update: 3dnews has written a article about it. Its in Russian but google translate works well enough. http://www.3dnews.ru/901747 I have also updated the forum links below with more forum threads about the problem. End of Update. To make the story short the SSD will over time lose Liner Read performance in data stored for a long time. So you windows files, games, programs that are pretty static will reduce in read speed after a few months usually and then degrade rapidly. This is not how SSD's usually behave since the technology it self usually allows read speeds to stay unaffected but writes can degrade for a number of reasons. Data that is new will show full read speeds so benchmark programs that write temporary files for reading will not show the problem. I know a few forums where users have started to collaborate on the problem and I will give links to them down below. http://forums.overclockers.co.uk/showthread.php?t=18615995 http://www.overclock.net/t/1507897/samsung-840-evo-read-speed-drops-on-old-written-data-in-the-drive http://www.reddit.com/r/buildapc/comments/2g1jfi/seems_that_the_samsung_840_evo_is_notorious_for/t3_2g1jfi http://linustechtips.com/main/topic/214537-samsung-840-evo-ssd-performance-degradation/page-3 If y our a member on any of those forums I and you are effected by the problem I suggest you make a post. So the long story is that this is a unusually problem with an SSD since read speed even on a badly misaligned SSD should still be very fast but the 840 EVO and 840 can drop to 50MB/sec or less and for some go down to a crawl of 1-2MB/sec on some old files meaning it only gets a fraction of its max speed fresh out of the box. Problem is not just during benchmarks but confirmed by many that real files actually reads slower. I have been involved with many effected users in IRC and other forums so its a big problem and not just a few effected users. I my self own an 840 EVO and an 840 but also have access to another 840 500GB that is 1.5 years old that runs at an average 50MB/sec on about 1/5 of its storage space. Theory's on the problem are many, bad ware leveling that places old static data in a way allowing slower access like only on channel being used from the controller. Others think the TLC is bad some how others thinks its a TLB bug with the look up table. Samsung seems to be investigating but since there support is supplied by a 3:e party its hard to say what they are actually doing about it. Over at overlocker.net a user developed a program that will allow on to test any files for read speeds to make it easier to find effected files instead of manually copying files to ram disk or an fast realiable SSD. I my self have contacted samsung support. I have also contacted sweclockers.com and nordichardware.se and they are looking in to it since they found the evidence very compelling and will have drives available for testing later. Dont know yet what will come of that tough but I hope for an article. Here are some images on how an effected 840 or 840 EVO will look like in HD tune 5.5. This one is a 1.5 year old 840 500Gb running windows 7 premium installed the normal way (no cloning etc) so TRIM is on (Dont effect reads any way) and should be aligned properly since windows 7/8 is SSD aware. It runs on the Intel Z77 Sata 6Gbit port Some images of the same SSD using this program a user at overclock.net wrote. I suggest using the trail version of HD tune 5.5 to test out the problem. To get the speed map you have to wait for the read test to complete once thats done you can click on speed map. HD Sentinel 4 also works but its speed map is not as visually representative but its graph benchmark is just as good. Samsung support has apparently got multiple calls about the issue and they recommended using this link if you want to submit a complaint about the problem https://contactus.samsung.com/customer/contactus/formmail/mail/MailQuestionGeneralNew.jsp?siteId=592&PROD_ID=G303850 For those that want a temporary fix to speed things up can either defrag the SSD. Yes you should not do that to an SSD since it has no purpose on a "proper" working one but since rewriting the data on the 840 and 840 EVO regains some if not all off the lost performance temporarily a defrag will re-orientate the data since the defrag program assumes its a hard drive and realy has no control over what LBA's is addressed to what cells since the SSD will change that all the time to even out any ware on the cells. Also using Secure Erase will work but for some max performance have not been restored but a new some what lower base line. But Defrag rely only works once on static data since the defrag program will think the data is ordered systematically since it dont know how an SSD works. Secure erase should work every time but doing that every 2 months realy sucks. And I have spoken with users that have done it 2 months or so ago and its not a long term fix even if some users seems to think so but thats simply because the problem takes a few weeks at minimum to manifest again. So I urge you all to test your drives, you can post dumps of HD tune 5.5, HD Sentinel 4 since they read existing data of the SSD. There are other programs that do this to but you must know for sure that this is the case when you test. IF it writes data to do its read test performance will not be effected since what ever is wrong is done to the data after a longer period of time. This issue is not a small one and even people thinking this is a user error have found there 840 and 840 EVO effected once they have tested them and just like me people owning two or more have found most if not all of there 840 and 840 EVO effected by the slow read speed on old data. I my self have own other SSD's (intel 320, Crucial M4) and non of them have them has this problem. It only seems to be Samsung TLC based drives (840 and 840 EVO), MLC drives for other manufacturers and from Samsung so fare has not shown the problem so no need to worry about other units.

Yea I have suggested the same thing many times and unlike what some think it should be fairly easy for a programmer to set it up I believe.

Yea my dropbox account got baned so had to fix that and remove those files. I had en accident so been sick the past week or so, mostly bed rest. Before that I had to RMA my Monitor, dead pixels and stuff. So have hardly played 0.24 since it came out. See if I can drop some more of them on dropbox later but I cant have them there for to long or my 20Gb per day limit will get me baned again. And a BIG thanks to Overfloater for uploading them to youtube! Music and Video is under CC license that what I always intended to reuse is allowed as long as credit is always given to the creators for the music and video. Overfloater wrote that out in the description so should not be hard to figure out if any one wants to remix or share them in some way.

Only thing that we realy need is intercoolers and proper intakes for them. ATM any jet engine can go at any speed pretty much with out overheating. Real world jet engines will overheat due to friction at high speeds causing the intake air to overheat the engine. After all even a jet engine can only run so hot and needs relatively cool intake air to cool some of its sensitive working parts like bearings, turbine blades etc. Plus the hotter the intake air the less fuel can be burned to produce trust since the amount of fuel dictates turbine temperature. Jet engines are primarily temperature limited. So any way an intercooler is needed and a proper intake for the rapier engines. Now I my self use jets extensively for SSTO's and they make it possible to go anywhere in an SSTO in the solar system and back with payload and no refueling BUT its a bit unrealistic for the final game to have jet engines going that fast relatively speaking. So for game balancing Intercoolers and special intakes would be nice. Now intecoolers could be used with JET engines to. The SABER engine has been proposed as a aircraft engine mode only version that still could do Mach 5 but do not have the rocket mode. So I think for best balancing we need intercoolers, they are the heaviest part so they should be heavier then the engine they also require a proper intake for most efficient use. Esthetics's and drag reduction. They could still be used with both JETS and RAPIER but with out an intercooler per engine the max speed should be mach 3-4 before overheating at 100% throttle and with intercooler mach 5-6 should be doable before overheating. SQUAD would need to add the intercooler part at a minimum and all jet engines an rapiers would need a max speed with and without intercooler that also factors in fuel use in to the equation to determent the engine temperature and thereby when the engine would fail and go in to a broken mode.

Simplest fix for this is to start out with the Fuel tanks. Mount them in parallel instead thats the easiest way to maintain CoM. Second option is to use a forward tank and a rear tank and use pipes to make sure they drain equally. A center tank can be used to in this configuration with proper piping. But the parallel method is the easiest to master. Once you have your tanks placed add engines and cockpit and make sure CoM is in the cetnter of the tanks then add wings in such a way that the craft maintains CoL appropriately. Lot of people wants CoL rear of CoM but thats not necessarily better in KSP from my experience. Many of my best crafts have had CoL forward of CoM. Also a good idea to rotate the craft 90 degrees on it side and check CoL. It can shift significantly forward or rearward that can cause the craft to spin out of control during roles and turns. Add rudders etc to compensate for this if needed.

Well rigth now one gets to much money doing missions and also to little sciense doing a full DUNA or Mun contract in my book. Howl thing is unbalanced. I have like 4 millions now I think and Im still working on unloc king the new tech tree, have not been playing much at all the last year. I built mostly SSTO's back in 0.18-0.22 but in sandbox you can make tons of money even with a crappy rocket built in less then 5 minutes. Contracts atm are unbalanced, pays to well in some cases and contracts that are in teh scope of the real Moon landing and proposed Mars landing hardly gives any Science points except for what you can collect out side the mission parameters. I make more money and science by just sending probe cores and some times kerbals by just having them sling shoot by Mun, Minmus or Duna and then fly back home again collecting science and testing parts on the way. Making money is way to easy and contracts are way to boring and illogical.