Temstar

Pitch up or down during reentry is a sign of too much weight at the rear of the plane I think. It\'s like how a shuttlecock always turn so that the heavy end faces downwards as it falls. All that fuel at the back of the plane plus three dead engines is really pushing the rear of the plane forwards fighting the control surfaces to get in front. If you have a lot of fuel left it would be a good idea to do some non-necessary orbital maneuvers to burn up the excess fuel before attempting reentry. Maybe they should give us a fuel dumping gadget in the future. =P

10,000m above ground on Earth is nothing like 10,000m above ground on Kerbin. Earth\'s exosphere is at least 100,000km above the surface, on Kerbin you\'re out of the exosphere once you\'re above 70km. 10,000m above Earth puts you in the troposphere where most planes fly. 10,000m above Kerbin is probably either upper stratosphere or the mesosphere where jet engines are not even suppose to work. You can see that because the basic jet engine only works till about 6,000m. That turbojet is actually an incredible piece of engineering being able to produce thrust till 20,000m. To put that into perspective that 20,000m on Kerbin is like 100km+ on Earth in terms of atmosphere density. SpaceShipOne had to use rocket engine to just get that high at the apoapsis yet here you have an air breathing engine that can still produce thrust at what would be considered beginning of space on Earth. On top of this those jets have physics defying thrust to weight ratio. Air breathing engine is always going to have lower thrust to weight ratio compared to rockets because they need a heavy and complex air intake which rocket engine avoids completely. Air is what 1000+ times less dense than liquid/solid oxidizer so the plumbing involved in getting outside air into the combustion chamber is enormous compared to what\'s required to pump liquid oxygen into the combustion chamber. In KSP that turbojet has better thrust to weight ratio than every other engine except those RCS thrusters. That\'s why it\'s so simple to build SSTO in KSP compared to real life.

You\'ve been given bad advices bro Right, that\'s bad. The idea of a balanced plane is to have the center of lift right on the center of mass. Center of mass is pretty easy to understand, center of lift is the sum of lift from all your wings and control surfaces. For example most planes have a center of mass towards the rear of the plane because all the heavy stuff like engines, fuel and fat sections of the fuselage is at the back. That means when you add wings to the aircraft you got to add it so there\'s more lift at the rear at the plane then front. Hence why delta wing aircraft have the main wing at the back and the smaller canards at the front. The best way to tell if your center of lift is exactly where your center of mass is is to fly straight and level with no control input. If they are matched then you nose will neither pitch up or down. The tricky part is shifting center of mass - remember as you use up your fuel gradually the nose of your plane become lighter than your rear. You need to counter this with trim and clever engineering. In KSP one way is to make your nose a bit heavier so at take off the tendency is to pitch down slightly. Counter this with trim and half way through your flight the center of mass will be exactly on center of lift. Towards the end if your flight your rear will be heavier again so you have to counter by trim in the other direction. Those are called canards. You use them if you need lift at the front of the plane. They improve the plane\'s maneuverability by giving you two separate set of horizontal control surfaces. Delta wing aircraft have a problem getting their nose up at take off and the canard is there to help with that by providing lift at the front of the plane. Don\'t angle them, see below for why. Don\'t do that, use vertical stabilizer for this. V-tail is used in real life by things like F-22 but they make the control much more complicated because when you move their control surfaces they introduce both yaw and pitch force rather than one or the other. If you want only yaw or only pitch you need a very complex control system (usually fly-by-wire) which can cancel yaw/pitch of one tail with the other. I personally doubt KSP can do this properly. So stick to either completely horizontal or completely vertical surfaces. Remember, you MUST have at least one vertical control surface on your plane or it\'s going to be unstable since it has no control over yaw forces. Wrong again, basically if you put landing gear behind the main wing you ensure your plane will never be able to nose up at take off unless you have canards and said canards are generating so much lift they can lift 50% of the weight of the plane by themselves. That\'s a hard ask for canards considering their size compared to the main wings. Remember when a plane nose up at take off they do around the wheels of the main landing gears. So the more aft the main landing gears are the more weight the plane have to lift before the plane nose up. Imagine it this way: if the main gears are exactly at the center of mass of the plane and we retract the nose landing gear then the plane will be on a precarious balance like a seesaw. It will only require a tiny bit of force to tip the nose (or the tail) of the plane up. Conversely the further away the main landing gears are from the center of the mass the harder it becomes to tilt the heavier half of the plane up. Whoever gave you those advices are off the mark four for four

No I don\'t use the RCS to reach orbit. I had intended to use this craft as a shuttle in the future when docking comes into play and the RCS will be for translation when docking. After all the whole point of SSTO is to get people and cargo cheaply into orbit by not dumping any rocket parts. I originally put on SAS to counteract a mysterious yaw force. Eventually I discovered the reason: my fuel lines confused the game as KSP can\'t handle two fuel lines coming out of one tank, it will just use one of the two lines. This caused one side to hold more fuel than the other and hence the yaw. I fixed this issue but forgot to take the SAS off. After flying the plane without SAS I agree they\'re not needed. It makes sense lightening the plane even by a slight bit will greatly improve fuel left upon reaching orbit. The hardest thing about making a SSTO both in real life and KSP is to get the propellant mass fraction high enough. For Earth a craft needs 25 to 1 ratio fuel to vehicle hardware ratio to be able to achieve SSTO. On Kerbin it\'s a lot less, I calculate the current incarnation of Dreamchaser to be: Empty: 15.16 Take off: 25.76 So in other words, almost 42% of the planes takeoff weight is fuel. If you add on two SAS it becomes 16.76/27.36, which worsens the propellant mass fraction to slightly above 38%, hence why the plane suddenly have a lot more trouble reaching orbit. Surprisingly removing the SAS also seems to improve handling somehow as I suddenly feel a lot less 'phantom force' when in orbit. Anyway back when I made Dreamchaser I didn\'t know about the brake button. Now that I do I realize I only need one drag parachute (if any). So in addition to removing SAS I\'ve cut down the number of parachute to 1. I\'ve also made some improvement to the flight program: [list type=decimal] [li]Turn on Adv SAS to keep the plane centered on the runway, max throttle and hit ignition on the turbojets. Upon reaching the end of the runway turn off Adv SAS and pull back on the stick. Once the plane leaps off the end of the runway it will nose up. Alternatively if you miss the end just keep Adv SAS off and after gliding on the grass a bit it will pitch up.[/li] [li]Pitch up to 60 degree angle and let it climb[/li] [li]At 12,000m, hit stage to fire up the aerospike rocket engine[/li] [li]At 19,000m disengage the jet engines[/li] [li]At around 50,000m you will have an AP of about 60,000m. Disengage Adv SAS and pitch down to horizon. By the time you pitched down the AP will be about 70,000m which[/li] [li]Keep your nose on the horizon and keep the engine running until 2,000m/s[/li] [li]Wait till T-30 till AP and fire up the engine again to 22,000m/s. After that do small burn as you near AP for final circularisation[/li] Manage to reach orbit with about 350 fuel left. Still room for improvement of course. The ideal will be to reach orbit with one continuous burn. If you find a better flight program let me know. Attaches is the improved Dreamchaser Block II.

Delta wing aircraft tailstrike is a well known problem and a 4th tailwheel is actually quite a common solution. Here\'s a picture of Concorde with its tailwheel deployed.

If you go watch Apollo 13 again the FDAI and danger of gimbal lock came up a few times in the movie. If I understand correctly the ship is set so that gimbal lock range is set at the north and south poles of the ecliptic plane. That is the directly 'above' and 'below' the sun as viewed from the plane of earth\'s orbit around the sun. The idea is in a normal mission you should never need to point the Apollo spaceship directly 'up' and 'down' in respect to the ecliptic. Of course with Apollo 13 venting oxygen and RCS thrusters firing wildly trying to compensate for the venting the ship was tumbling all over the place. There\'s a scene where CAPCOM was telling Jim Lovell to 'watch that middle gimbal' and Jim who was frustrated trying to bring the ship under control was all 'Yes we\'re well aware of the GODDAMN gimbal, I\'ve got the damn thing right in front of me!' Fun fact: Jim Lovell, Neil Armstrong, Buzz Aldrin, Michael Collins and a few other Apollo astronauts came from the Gemini program, and just like our own Command Pod Mk1 the Gemini spacecraft DID have a 4th gimbal so it didn\'t have this gimbal lock problem.

The Apollo ones are called FDAI: Flight Director Attitude Indicator. The crews call it the '8-ball' http://www.space1.com/Artifacts/Apollo_Artifacts/FDAI/fdai.html The Apollo crews had it hard. See that red area on their ball? That\'s the gimbal lock range where two axis of the gimbal are aligned and will cause the loss of attitude reference for one degree of freedom. The Apollo crews are trained to always avoid pointing their ship in this area. If gimbal lock does happen the crew will have to move the ship out of gimbal lock range (blindly, without a working FDAI) and reset the FDAI using stars as reference. Has this happened on Apollo 13 they would have been stuffed since all the debris floating around prevented them from seeing the stars properly. This problem could have been resolved with a 4th power driven redundant gimbal but MIT guys told NASA it wasn\'t worth the weight and complexity in their opinion. While Neil and Buzz were walking on the moon Mike Collins aboard the Command Module joked 'How about sending me a fourth gimbal for Christmas?' So yes, be glad our nav balls have a fourth gimbal

Remember also, our sun is a G-type main-sequence star, where as Kerbol is a M-type red dwarf. Kerbol\'s energy output and solar wind are weak sauce compared to our sun so comets will need to be much closer to develop a tail.

Here\'s my landing site:

So on today\'s trip to the Mun I spotted a very unusual object near my landing site: I decided to fly closer for a better look and this is what I got: Now if I recall my high school geography right, arches can only form in nature from wind/water erosion. Since Mun doesn\'t have atmosphere or liquid water how is it possible this object came about?

Comets can get that big, this guy http://en.wikipedia.org/wiki/Comet_Hale%E2%80%93Bopp for example is the same size as Minmus

I use two turbojet engines to climb at 45 degrees. Then at somewhere between 8,000 to 9,000m I fire up my rocket engine and pitch up to about 60 degree to get up above the atmosphere as fast as possible. At 19,000m I switch off the jet engines and go purely on rocket. Then at about 40,000m I pitch down to pick up more horizontal speed. The spaceplane I use is: http://kerbalspaceprogram.com/forum/index.php?topic=12625.0 Surprisingly the weight penalty from bringing two deadweight jet engines from 19,000m to 70,000m is more than offset by the fuel saved in the first 19,000m, especially the first 8,000m where the plane uses pure jet power. I tried the same plane with two rocket engines and it can\'t even make orbit.

Cos I was thinking of using it as a drag stripe and need a way to accurately measure top speed and acceleration over a set length.

I aimed for the ultimate aim of SSTO - airline style horizontal take off and landing. After spending better part of the day working out the bugs I\'ve finally come up with a working craft. Orbiting burn guideline: 1. Turn on Adv SAS to keep the plane centered on the runway, max throttle and hit that spacebar and listen to the turbojets roar into life. Being a big fat SSTO Dreamchaser is quite heavy, so no need to nose down on the runway. 2. The runway is actually a little bit above the ground. Nearing the end of the runway flip Adv SAS off and pitch up. As the wheels leave the runway the plane will nose up. Immediately switch Adv SAS back on and the plane will start climbing. Retract landing gear. 3. Pitch up to 45 degree angle and let it climb 4. At 8,000m, hit stage to fire up the aerospike rocket engine. 5. At 19,000m disengage the jet engines. Around this point there should be some pitch instability due to fuel being used up in the forward section of the side stacks and loss of effect from control surfaces. if Adv SAS can\'t handle it turn it off monumentally and control your pitch manually. The instability should be fairly short lasting. 6. Once apapsis is at 70,000m, do an engine cut off and perform a course correction and nose down to the horizon. 7. Wait till about T-30 seconds till AP and fire up the engines again to build speed, get to about 2,000 m/s and turn off the engine again if AP is still ahead of you. 8. Nearing the AP, fire the engine again for final circularisation. I haven\'t touched C7 before so I\'m still practicing landing with a trainer, but this plane should have plenty of lift to glide down to KSC runway particularly with empty fuel tanks. The drogue parachutes are reinforced and rated for up to 130m/s for a 6G deceleration, do not deploy chutes at greater than 130m/s. Rocket engine kicking in Course correction and waiting for AP

The turbojet says something about ramjet intake. Maybe in the future it will work like this: turbojet + circular intake = normal turbojet, works for say <15,000m turbojet + ram air intake = more powerful ramjet, works <25,000m, has reduced efficiency at high air density and/or low air speed basic jet + circular intake = normal jet basic jet + ram air intake = explosion

Aerospike IS a rocket engine, even in real life. Aerospike rockets have the exact same machinery as normal rocket engine (fuel and oxidizer turbopump, combustion chamber, regeneratively cooling, etc), it just has an unusual nozzle that\'s more efficient at a wider range of altitudes.

If you have canards get rid of them. Canard + vectored thrust engine results in Su-30MKI style supermaneuverability which allows you to perform post-stall moves like flying forward with engine pointed in all kind of wield angles: The problem is supermaneuverable planes cannot be controlled by manual control, you need fly-by-wire controls which is something like an Advanced SAS except it doesn\'t fight the pilot. It constantly applies slight input to control surfaces and engine thrust angle to counteract instability while still responding to pilot input. We don\'t have something like this in KSP so flying a supermaneuverable plane is nearly impossible.

So for the Mun, given it\'s physical properties we know it probably originated the same way as our Moon - http://en.wikipedia.org/wiki/Giant_impact_hypothesis. So what about Minmus? How do you think it came about? Me I think it\'s a captured comet nucleus. Minmus seems to contain a lot of ice on it\'s surface but it\'s far too small to be an Europa analogue. The inclined orbit and small size seems to suggest it was captured by Kerbin\'s gravity in the past. Only problem with this theory is its orbit is too well circularized. If this thing is a dirty snowball from the outer planets then after being captured you\'ll expect it to have a pretty elliptical orbit. That said both Phobos and Deimos are likely to be captured asteroids yet both have a very circular orbit right on Mars\'s equatorial plane, so there would well be a mechanism to circularize captured objects.

I was expecting the jet fuel to be different to liquid rocket fuel like how liquid rocket fuel is different from RCS monopropellant so I was very surprised to find out they\'re actually the same. That makes no sense, jet engines need avgas or kerosene were as rockets use LOX/RP-1 or LOX/LH2 or some other more exotic mix of fuel and oxidizer. Even though RP-1 is very similar to kerosene the tanks for rockets will be very different to fuel tanks for jets and shouldn\'t be compatible.

Is it just me, or is that new aerospike engine a bit overpowered? I ran test on all my boosters from fast accelerating light lifters to lumbering heavy weights and in all cases replacing LV-T30 with aerospike noticeably improve rocket performance. That extra bit of weight is nothing when you look at its thrust and fuel efficiency. Then I thought maybe this engine is suppose to be hard to place since it can\'t sit on top of decouplers, rendering it only useful for parallel stage side boosters or very cleverly engineered rockets, turns out my 12-tanks-to-LKO orbital tanker was perfectly happy sitting on the pad on top of 6 needle thin spikes. It would seem possible also to setup aerospike engines for upper stages for giant rockets too by using decoupler only in the center stack and have the aerospike engines clustered around it and attached to the below stage with struts (might get a bit hairy during staging), so what\'s the point of LV-T30 now?

With 0.15 out we are now able to add landing legs inverted without fooling around with karts. So I ran a quick test on docking again with a test rocket. Here is my test ship. The aim is to grab the nearly spent rocket stage behind me with either set of legs. So the idea here is to see how well I can dock with forward vs reverse landing legs. Immediately in VAB I noticed a difference - you can\'t get as tight of a grouping mounting legs backwards on fuel tanks or even decoupler as you can forwards. In the above picture you can see the difference. Notice how I was able to place the forward legs so far inside the decoupler that the pivot is almost flush against the decoupler wall, where as the rearward legs can only be attached onto the wall of the tank. The rear legs are easy to test, I just have to keep the legs closed and stage. Unfortunately it turns out there\'s no grip at all on the rearward facing legs, the rocket stage immediately slips out. So it\'s onto the forward set. After reloading I flipped the spaceship around and inched my way inside the decoupler nose first. Success, the forward landing legs were able to firmly grip the decoupler. Wobbling the spacecraft around pivots the rocket stage in front of me without any loosening of the grip, looks like a pretty firm dock. I then turned SAS off and the ship started rolling like a top. Even turning SAS back on was barely able to bring the ship under control. I turned SAS off again and sure enough the rolling started again. Leaving the SAS off resulted in the ship rolling faster and faster until the forces involved violently tore both ships apart. It seems like the spent rocket stage is somehow exerting a rolling force on my spaceship without any source of acceleration, physics engine bug? I don\'t recall this happening in my earlier test docking two crewed spaceships, maybe this only happens with debris? Next step I plan to put a large spaceship in orbit and then try to dock to its tail with a smaller spaceship to test stability. If docking is successful and there\'s no miraculous force trying to spin both ships I\'ll then try to do an orbital maneuver. If that\'s successful then I say we\'ve found a way for Apollo style Munar Orbit Rendezvous mission. Test ship is attached for those wanting to try for themselves.

A local council in West Australia fined NASA for $400AUD for littering when Skylab came down. True story

I made a thread about docking with landing legs here: http://kerbalspaceprogram.com/forum/index.php?topic=12026.0 Now about those legs. From my experiment that arrangement above is not that good. Together the six legs will prevent any lateral movement between the two spacecraft (within reason, I\'m sure if you really tried you could break them). However they don\'t really 'grip' the opposing ship as such, so if the two ships where to move apart without any lateral movement then the two arms will slip off. How I thought very long and hard about this and this is the improved docking arm I came up with: The improvements are: [li]Tip of the arm now uses decoupler rather than fuel tank, this is because decoupler seems to have a bulging mid section for the claws to grip onto[/li] [li]claws are now placed at the very tip of the decoupler right on the lips, improving length of the grip as well as make the legs close together tighter [/li][li]notches are added on the arm to provide some traction for the claws to grip onto[/li] [li]increased number of claws per arm from four to six to increase strength[/li] When I get some free time I\'ll try the docking again and see if this makes things better. If it works I\'ll try to connect four spaceships to that station (notice I put a passive 'female' docking arm on the tail end of of that craft). If the improved 'hand to hand' docking turns out to be firm I\'ll try the male-female docking and see how that works. If it also turns out to be a solid dock then Munar Orbit Rendezvous mission profile for Munar landing is a go.

You have to make the final approach very nearly front on. Don\'t try to dock at 45 degree angle and counting on the legs to correct your ship because they will just snap. Of course the tricky part about this is a ship without pilot focus will have Adv SAS off so it will drift all over the place. Jumping in between the two ships trying to correct them will help but it still takes a lot of patience and a little bit of luck. If your position doesn\'t look right don\'t force it. Back off and realign the ships. That dock was the 5th attempt. Of the previous four attempts two slipped out, one my legs didn\'t grasp the arm and instead bumped the target ship and sent it spinning and one I broke off one of the legs when closing them and had to reload. Here is a shot of the docking right after I deployed legs before the legs could lock my ship into position. As you can see I had the two docking arms nearly lined up before closing the legs.

Hand holding at 75,000m Kerbinrise