Loren Pechtel
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Posts posted by Loren Pechtel
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1 minute ago, Plusck said:
Oh, but it will. The boosters are already connected low down on the central stack. Adding a strut from the top of the boosters to higher up on the stack will make triangles radially around the rocket which distribute the forces exerted by your gimballing engine and your torque wheels. It will most certainly reduce the wobble that is visible in the pic you posted.
Once you are out of the thick atmosphere and lose your boosters, you should need less control input anyway. You can right-click your central rocket engine and toggle gimbal on and off as required. You can also switch SAS on and off to dampen the wobble.
One big reason for wobble is that the part doing the controlling is at the very top of the stack, together with the torque wheels. To turn, the torque wheels push one way and the engine vector changes to push the other way. However, due to the large number of weak joints the top will start moving quite quickly, while the middle of the rocket is still pointing in the original direction. The controlling part "feels" this movement first, and reverses the movement to stabilise at the new heading. However the springiness of the joints makes it snap back too quickly, so it again reverses the movement... and meanwhile it is telling the rocket engine at the other end to do the opposite. This sort of oscillation is unavoidable with SAS on the best of rockets, and on a noodly one it can rip the whole thing apart.
Next bird I will try strutting that way. Is there any other fix beyond unlocking fatter rockets?
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11 minutes ago, FullMetalMachinist said:
I would get rid of those struts and instead strut from to tops of the radial boosters to the central stack. However, that type of instability that needs fixing with struts is one of the hallmarks of an inherently unstable rocket, and maybe should be redesigned using the tech that was unlocked by the previous mission. But if you're set on using this rocket again, then struts from the radial boosters to the center should help. Be sure you go from the outside in, and not the center out with the struts. The part that you first attach a strut to gets all the weight and drag of the struts applied to it, and the little nub that remains after separation continues to add weight and drag to the parent part. So if you go from the center out, when you decouple the boosters, you won't see the struts any more, but the little nub will still be there, taunting you with increased drag and mass. Better to attach them to the boosters first, where those pesky nubs will fall away with the spent stages.
Thank you, although that will do do nothing about the wiggling I saw in the central stack.
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28 minutes ago, Snark said:
Just to take a step back, here... rather than simply trying to fix the rocket, is it worth trying to fix the problem? i.e. what's the purpose of this vehicle?
Reading between the lines (apologies if I've missed something along the way, the thread has gotten pretty long at this point), I gather that what you're after is a vehicle that can schlep four tourists to orbit and back home, and that's pretty much it, yes? Maybe some science along the way, as a low-hanging fruit, but mainly what the ship is about is "get four tourists to LKO and then home again", yes?
So, my suggestion: rather than trying to fix a particular design, start with the payload and design up from there.
Your center core is a great idea. Command pod, couple of crew cabins. Decoupler so that it's the only thing coming back, good. I would suggest putting a pair of AV-R8 winglets left and right on the rear of that vehicle-- it will give you steering ability on reentry. If you're only going to LKO, you can get by without a heat shield, as long as you have good steering ability so you can make maximum use of body lift. You could even stick a couple of fixed fins on the middle of the craft, around the CoM.
So that's your reentry vehicle. What next?
Below the decoupler, you put your upper orbital-insertion stage. Suppose this is two of the 2-ton LFO tanks with a Terrier. (I'm guessing you have to stack 'em because you haven't unlocked the tall skinny 4-ton tank yet.) So at this point you've got a craft that's probably somewhere around 8.5 tons, carrying 4 tons of fuel. With a Terrier, that's over 2100 m/s of dV, which is 2/3 of the needed dV to get to orbit, right there. So all you need to do is give that thing a boost of a bit over 1000 km/s and you're good to go.
Let's say, for example, that you put 3 more of the 2-ton tanks under it, with a Swivel. That'll raise total mass up to around 17 tons, of which 6 are fuel in that stage, so you'll get on the order of 1300 m/s dV. When you build that, disable the top two tanks so that the bottom tank will drain first. Your craft is really going to have some aero stability issues with that light, winged thing up at the front, so give this stage four of the AV-R8 winglets, put just as far to the rear as you can manage.
Theoretically that's enough dV, but it's pretty low TWR and we'd like to have some safety margin. So now comes the MOAR BOOSTERS part of the design. Strap on four radial Thumpers around that bottom stage. With decouplers, nose cones, and maybe some more AV-R8's at the back of the boosters, that brings your total ship mass up to something like 48 tons. If you want launchpad TWR of 1.5, you'd set the thrust limiters on the Thumpers to around 70%.
That ought to get you to orbit just fine, with a much lower part count. Take off on the SRBs; by the time they burn out, you're already pitched over at 45 degrees or more, and the relatively low TWR of the Swivel stage won't matter as much. Just remember to enable the tanks on that stage as the bottom one drains, so you can keep continuous power.
(Actually, you could give the SRBs a bit more legs by setting up the four radial boosters in two pairs. Instead of setting all four of them to 70%, you can set one pair to 85% and the other pair to 55%, so that the hi-power pair ditches runs out of fuel and ditches first. Sort of a poor man's asparagus.)
Anyway, just a thought.
It wasn't meant to be the prototype of a class, I was just building a rocket to gather as much science and contracts as practical. The only craft I've made more than one of is the little science rover I sent around the launch complex--I built a second one after unlocking more instruments to put on it. (And then I build a third similar one because I got a contract to test the Juno engine while splashed down. I drove it slowly into the water and tested the engine. Since I now had a radial intake on top the engine still worked--and somehow so did the steering. I was expecting to recover it from the ocean but I was able to drive it back to the runway.)
31 minutes ago, FullMetalMachinist said:Well, one option is the Kerbal Joint Reinforcement mod. It takes the stock joint reinforcement that happened in 0.23.5 and pushes it even further, making all your joints between parts even more rigid. Now, there are some very well respected users on the forum that would say that KJR is more of a crutch, and that if you need it to function, then it's really a sign that your basic rocket design needs improvement. I'm not refuting that opinion, just pointing out that differences between players exist.
Another option is careful, strategic use of connector struts. The main thing to keep in mind when using struts is that they add a lot of drag, so use as few as you can get away with while still making your rocket more stable.
The last option is perhaps the least attractive. Basically redesign your rocket from top to bottom, keeping in mind the whole time that it should look and behave like a real life rocket. This is fairly difficult, and at times counter-intuitive. If you have a design that you're mostly happy with, but is still wobbly, you can upload the .craft file somewhere (dropbox, google drive, kerbalx.com) and let myself or other players try it out, and modify it if necessary, to give you some ideas on what works and what doesn't.
Other than that, useful screenshots and very descriptive problems usually get the most useful advice. If all else fails, keep trying. This game is not for the faint of heart, and can seem a bit daunting to begin with. But it is so worth the effort when you do something awesome for the first time. I'll never forget the accomplishment I felt when I first landed on the Mun. So just keep at it, you'll get better with practice, and there are plenty of helpful players on the forum when you have problems.
I strutted between the outer engines, it didn't help. Where should I strut?
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8 minutes ago, FullMetalMachinist said:
Sounds like you were able to more or less brute-force your way through that contract & orbital experience. That's a big part of this game, trying different stuff to see what works and what doesn't. I'm glad that you were able to end up with a favorable result. And sorry that I couldn't give quite good enough advice to make it easier for you. If you have any other specific troubles, start a new thread, or keep adding to this one, and those of us on the forums will do our best to help you out.
What's the cure for a wobbly rocket like that one was?
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9 minutes ago, FullMetalMachinist said:
In that case your problem is either that your reentry angle is too steep, or your ship is not wanting to point any direction but prograde. Meaning that you're either not spending enough time in the upper to mid levels of the atmosphere to bleed off some speed before you get really low, or you're "lawn darting" into the ground, yes? Ideally you could just keep your engine pointed retrograde and let it slow you down, but I assume you've tried this and it didn't work?
To fix the first problem is relatively easy, just raise your periapsis that you reenter at (you are coming in from low Kerbin orbit, right?).
The second problem is a little more tricky, and might necessitate a slight redesign of your rocket. Even if you're not exploding on the way in, I would still suggest trying the 'head shield on top' design. They are quite helpful at shedding speed as well as heat, and also can give you the chance to turn your rocket away from prograde, exposing the big belly of your craft, which gives you some body lift to counter your speed even more. To that end, you could try adding the AV-R8 winglets to the bottom most part that you will be reentering with, to give you some more control authority than just the reaction wheels inside the command pod in order for you to, again, point away from prograde to take advantage of body lift to slow you down enough to deploy 'chutes. Note that adding winglets to the front of your craft may make it more unstable during launch, so be careful.
That was exactly what I was trying--after my deorbit burn I had about 1000 m/s left and used it on the way down. Just as it was running out of fuel I flipped and could never get back to tail first.
I put some struts between the boosters to see if that would help the wobbles. If anything it was slightly worse. Turning off SAS helps--but my first try that way caused it to flip like in the screenshot.
I managed to wobble my way up, although again with a bad turn. I ended up with my apoapsis over 400km but the contract only says "orbit", it worked. This time I jettisoned the engine at a higher altitude (and speed--I wasted even more fuel this time) and only had the capsule during the worst of the reentry. I was able to keep it tail first. It also helped that I came down over water instead of a mountain. All in all I earned about 4x what the rocket cost, around 100 science and 200 prestige. No comments from my tourists about getting more than they paid for. (The tourists were only asking for suborbital.)
I wish I could haul tourists around without such a long reentry capsule.
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12 minutes ago, pincushionman said:
I'm going to go so far as to say you have too much booster and not enough center stack. You have six massive boosters and a center stack that looks to be only as massive as two boosters. And the boosters are stacked tanks.
As a result, the CoM of each booster will move back as fuel drains, and there isn't enough mass in the center stack to "overpower" that action - especially if you're running the center engine at the same time (as its own CoM will also be moving back). Are you running seven engines, or just the six boosters? If you're running the center too, you probably have enough TWR to try it using only the boosters and using the center engine after you drop them.
Picture in the VAB, then drain all your first-stage tanks and compare the positions of the vessel CoM. I'm guessing it starts too far aft and doesn't exactly get better as fuel drains.
Also, describe your turn. If you're trying to turn more than a couple degrees from prograde at 350-ish m/s (sound barrier), you're screwed.
The outer boosters are to get me out of the atmosphere, the inner one is a Terrier--not worth lighting until I'm in space. The COM is basically in the exact center of the outside boosters.
I probably do have too much, I didn't switch back to 4 outer boosters after trying adding more thrust fighting the stuck in the launchpad bug. I don't understand about not enough center stack. It's got almost 3000m/s of delta-v and did what it was supposed to do, even covering for my late turn.
11 minutes ago, FullMetalMachinist said:So at this point the thing that was hurting you on the way up, is hurting you in the same way on the way down. Those two crew cabins are really light for their 1.25m cross section. That means that on the way up, they're fighting to be at the back, and on the way down, after you've staged everything away, the mk 1 capsule is the heavy bit, and the crew cabins are the light bit that again wants to be at the back. Which means you're heading in for reentry head first. Which is not good. One thing that you can try is to simply put a heat shield on the very top of your rocket. So instead of the mk16 parachute on top, put a decoupler, then heat shield, then nose cone to cut drag on the way up. You'll have to use radial parachutes instead of the mk16. On the way in from orbit, your rocket will want to point prograde naturally, thus putting the heat shield out front (the nose cone might blow up, but who cares?). After you've gotten past the hot part of reentry, decouple the heat shield, and try to angle your craft so that it has the long side toward the wind. This will give body lift, and help slow you down enough to deploy your radial 'chutes.
After you've gotten past this first bit of career, you can use fairings instead of the whole 'heat shield on top of your rocket' strategy. Though, note that in stock 1.0.5 the fairings have a bug where their lift and drag forces are placed way in front of where they should be, and thus make your rocket very flip-happy. Claw's Stock Bug Fix Modules fixes this, among other things.
The problem wasn't burning up--I got no temperature alarms. The problem is nose first there's not enough drag--I was going Mach 1 when I ran out of altitude.
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26 minutes ago, FullMetalMachinist said:
Are you playing career? If so, I would do my best to unlock the tech node that gives you the AV-R8 winglet. Replace all those basic fins with it (actually probably not a straight replace, I would get rid of all the Basic Fins and put one winglet on each side booster). It's steerable, which will help greatly with stability issues. Also, if you're using the LV-T30 "Reliant" I would switch them to the LV-T45 "Swivel", which has engine gimbal, which will also help. You're kinda setting yourself up for failure though. Those crew cabins are really light and draggy, and the back end of your rocket is really heavy with all those engines and fuel. Any way you can redesign to give it a more "arrow" like shape (i.e. straight, with weight at the front, and draggy fins at the back)?
On a related note, what does your launch flight profile look like? You mentioned that you flip even if you don't touch the controls. That could mean that you're just going straight up. Which is not the best thing to do. You can certainly get to orbit that way by going straight up to above the atmosphere then burning sideways, but it's really inefficient. A better flight path looks like a loooooong, gentle, continuous turn, until you get to orbit. Basically you start out straight up, but once you're going about 100 m/s or so, start a turn to the east by about 5 degrees. Then you stop touching the controls and let gravity pull you down into a long, gentle turn. At 10km you should be around 45 degree tilt, at 30km around50 or 60, and by 50km almost all the way over, pointed at the horizon.
Also you said that you flip at about 7km up. That's potentially a really critical part of your flight. Depending on your launch TWR (which you said was around 1.5), that could be about the time that you're breaking the sound barrier. Once you do that drag goes WAY up, and if your rocket is a little unstable, things could very suddenly go bad. I would suggest adding a bit more fuel to those side boosters to get your launch TWR down to something like 1.25. That will keep you from going supersonic until you're above 10km where the atmosphere is much thinner.
Hope this helps, and let us know about any other questions you have.
I do have that winglet, I'll try that and the different engines.
The reason for going straight up was being sure it wasn't anything I was commanding--I know I need to start turning by then but I have managed to spin rockets out by turning so I was eliminating that as a factor.
I made the changes you suggested and got a **very** wild ride to orbit. Starting at about 2,000m it practically shook itself apart (over-correction from the SAS, perhaps?? Or is my rocket too weak??) and when that calmed down it still shook as I started my turn. Since I turned late I did a very wasteful profile but I had enough extra that I made it to orbit anyway.
And I'm kicking myself for not putting a material canister on this, I thought I had gotten that data from suborbital flights but now I see otherwise.
And then things went very wrong in the end. I had quite a bit of fuel in the upper stage so I burned it on the way down to slow down. Just as it was about to burn out the whole craft flipped to nose first. I blew off the booster but I could never recover, I was coming in too fast for the chutes.
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On 2/14/2016 at 4:48 PM, Geromey said:
I`ve currently got an Asteroid in a low Kerbin orbit and i`ve attached lots of small parts to the asteroid. Because of the way asteroids work in KSP, its one big Refueling station, Mining the asteroid to refuel its supply!
Don't they eventually run out of fuel, though?
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12 hours ago, Streetwind said:
There's also still that old bug where sometimes rockets get stuck to the tier 2 launchpad (but not the other tiers).
Try using launch stability enhancers to lift your rocket slightly off the pad.
Yup, that was it. I put some launch clamps on and it took off like it should. Now to figure out why it wants to start spinning around at about 7,000m up. SAS on, I didn't touch the controls after launch and yet this happens:
That was the second spin, I didn't manage to grab a snapshot at the right instant the first time around. I added a second reaction wheel in case there wasn't enough authority in the first one but it did exactly the same thing.
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I'm trying my first orbital mission. Sitting on the pad I'm seeing a TWR of 1.59 (from MechJeb), throttle to full, launch and it sits there. As the engines burn the TWR goes above two--but it still doesn't budge.
As an experiment I put on 6 boosters around the core of 4 I originally was using. This time it sat on the pad for 13 seconds then lifted off--but not crawling into the sky like I would expect if it had just reached enough thrust to lift. Note that this design lifted at a lower TWR than the previous one still sat on the pad.
It also goes totally wonky at about 7000 meters. I tried adding more fins, no change. SAS on, I'm not even trying to do a turn.
3 tries, the same behavior each time.
This game has a learning curve about like real rocket science!
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5 hours ago, FullMetalMachinist said:
Curioser and curioser... That is an interesting problem. At the risk of sounding like a broken record, the fastest way for you to get useful advice and help is to post a screenshot. If you're unsure how, see this post. Another useful thing you could do is upload your .craft file to Dropbox, Google Drive, or KerbalX.
Confirmed. The staging was wonky. The culprit seems to have been the decoupler got grouped with the parachutes and pre-deployed them when it was fired. I fixed that and they didn't fry--but something was wrong. I had to manually fire both stack decouplers on the rocket, they didn't stage properly.
Also, I messed something up and didn't get credit for the SRB test.
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12 minutes ago, fourfa said:
Funny, I updated a third thing while you must have been reading. Last thing is if you're really REALLY not pre-deploying the chutes, then you're just going too fast when they deploy. Anything over 250m/s and they'll rip off with the canned "destroyed by aero forces and heat" notification. Not being able to slow down below 250m/s before hitting the ground - that's also pretty common particularly with suborbital flights. Early career players tend to launch those straight up, re-enter straight down hoping to land back at the KSC, and never realize that a long arcing trajectory is crucial to re-entering safely. That long arc is what gives you enough time experiencing atmospheric braking to slow down enough. I've done the same thing myself many times.
I learned that lesson simply going to the upper atmosphere and Google quickly enlightened me.
I do think it's likely something is messed up with the design and they are pre-deploying regardless of the staging setting, though.
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5 minutes ago, fourfa said:
"The housing burned away releasing the chutes" is not a thing I've ever seen happen, though it does sounds exactly like what happens when you accidentally stage the parachutes in space before re-entry. We believe you are not doing it intentionally - KSP has a problem that makes this happen all too often.
If you go to outer space and stage your chutes, absolutely nothing happens (yet). The chutes stay in their containers, and there is no visible change. But once you enter the atmosphere with staged chutes, a couple things happen eventually. The chutes have two tweakable bars if you right click on them: one for the atmospheric pressure at which it will initially deploy (partial deploy - dragging behind you but not fully extended), and the second for the altitude above ground at which it will fully deploy and slow you down all the way (1000m by default). The default setting on the second is usually fine.
The first - partial deploy - by default is set to 0.05atm, which is in the very very high atmosphere where the chutes are still useless, and if deployed there, will invariably be destroyed along with a notice like "your parachute was destroyed by atmospheric forces and heat." If you change that partial deploy tweakable before re-entry to 0.50 (well into the lower atmosphere, by which time ships will often have slowed down to the safe 250m/s deploy speed), you can safely stage your parachutes in space, and they'll just pop out automatically at a safe time.
What's KSP's problem? Well, its default behavior in the VAB is to stick the parachute staging on the same stage as your final ship engines and decouplers. This whole thing sounds precisely like you made a ship that goes to space (200km part test), and when you added the chutes in the VAB, they were automatically added to the same staging event as your part test. Unbeknownst to you, they "staged" or entered a armed, ready-to-deploy state. Nothing changed externally, and you didn't notice the sound of the chutes staging because it happened at the same time as a decoupler and engine activation. Then when re-entering at terrifying speed, the chute dumbly obeyed its default deploy threshold of 0.05atm, threw the chute out, and was destroyed.
Two ways to check or change it. One - the staging of the parachute (the chute icon on the right side of the screen in the VAB, or the left side in flight) should be on its own numbered stage, with nothing else with it. You might not yet have discovered that you can drag these icons around in flight (as well as in the VAB), re-order them, move whole stages up and down - give it a try. Second, you can right-click the chute in space and change it to 0.50 and see what happens. Let us know how it goes.
Now, that makes sense! I've been fighting it about where it put the parachutes in the stacking on that design ever since I deleted a cabin from it. They aren't stacked with the SRB but I could believe something has gone wrong and it's completely consistent with what I have been seeing.
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5 minutes ago, Plusck said:
I quite agree. It's embarrassing having to ask but that "streaming" and "message about them being destroyed" does sound very much like they have been staged.
The parachutes should not be cyan at any time. If they are cyan, they have been staged. If you get a message that they have been destroyed then (AFAIK) they have been staged. If they are cyan, right-click them and disarm them, then rearrange their icons into a new unstaged stage so that you can release them later.
If you hear an explosion and see fireworks and you shake all over the place and suddenly you don't have any parachutes, then it is indeed an overheating problem. But it doesn't sound like this is what is happening. Instead, it sounds like a staging problem.
I wouldn't have accidentally staged them repeatedly. I don't think I had my headset on when I was doing this so I wouldn't have heard an explosion but it certainly seemed to me like the housing burned away releasing the chutes which were of course promptly destroyed.
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34 minutes ago, Snark said:
The ideal tourist vehicle is basically just a Mk1 command pod, with enough Mk1 cabins slung behind it to carry the desired number of kerbals. (If you've got a probe core with SAS unlocked (like a HECS), you could dispense with the command pod and fly it pilotless.) Put some steerable fins on the back end-- the AV-R8 winglet is great for this, it's unlocked fairly low in the tech tree. This will make the craft nicely steerable while in atmosphere.
A craft like that can enter just fine from LKO without any heatshield at all: it's light, draggy, and generates lots of body lift. Just enter nose-first, keep it pointed 30 degrees or so above prograde, and body lift will be your friend.
If you're reentering really steeply, to the point where it's actually more punishing than return-from-orbit even though the velocity's a lot lower, then reentry heat could be an issue. Options include: 1. stick a heat shield on the front end, with a nosecone on top to help with drag during takeoff (the nosecone can just burn off during reentry), and/or 2. have a little bit of fuel and a small rocket engine left over, which you can use for retro-thrust to slow to manageable speed before reentry. Just a few hundred m/s of dV should be plenty.
Except that with proper design, it can actually be helpful for slowing down, because it's large, light, draggy, and good for body lift. You want your ship to resemble an empty soda can as closely as possible, in terms of shape and density, and an empty SRB is pretty good that way.
Doesn't have to be. Just empty it out. An empty SRB doesn't weigh much, it's not even required to get up to orbital speed, and the shape + mass are ideal for optimizing body lift on reentry.
Yeah, once I unlocked the Mk1-2 I saw that Mk1 + cabin(s) was lighter. I don't understand the advantage of leaving the SRB on, though--more mass, same cross section.
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10 minutes ago, FullMetalMachinist said:
Sorry if this has been mentioned and I missed it, but I have a question about this bit. Are the actual parachute parts exploding off of your ship, or is it just that the parachute icon in the staging list has turned red? I only ask because if you're using the mk 1 pod with 'chutes on the sides and reentering tail first, they really shouldn't blow up, especially if you have a heat shield.
If that's not the case, and it's just the icons turning red, then your chutes are fine. Don't worry, you wouldn't be the first to be fooled by this. All the red icon means is that if you deploy them at that moment, they will be burned up. All you have to do is wait until drag slows your ship down enough for the icons to turn green.
Hope this helps.
They are actually exploding. I see the chutes stream (I did not deploy them) and then get the message about them being destroyed. It even gets the one on the nose cone.
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3 minutes ago, Plusck said:
200km suborbital trajectory for an SRB test?! That is a vicious contract. I hope it pays well because yes, your options are limited to:
a) making it part of a much bigger mission (Mun fly-by or something) and pointlessly lug an SRB high into a Mun-encounter-without-circularising burn or something like that;
b) expensively making it very nearly orbital so that you can recover your people in one still-moist piece;
c) slightly less expensively abandoning a probe to certain death.
Yeah, I didn't realize the re-entry problems it was going to cause. I took my previous tourist rocket, added fuel and the SRB (and some science) and figured it would work. As I envisioned it, cheap--it would only add fuel and the part itself to the launch. It's not going to take that much more to make it nearly orbital. I could do it with fuel alone if I was sure of the numbers.
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10 hours ago, Snark said:
Decoupler tests just require you to stage the decoupler. If all your green check marks are checked, then staging it should work-- as long as you actually have the correct decoupler that matches what the contract is asking for.
Would be handy to see a screenshot of your SRB test ship-- I'm still having trouble picturing it from your description, are you saying you used the Mk1-2 command pod on it? That's the big 3-kerbal capsule, and it's a beast, it's crazy stupid heavy (weighs FIVE TIMES what the Mk1 command pod does), so it's best avoided unless either 1. you have a strong reason to need it (like it's specified in a contract), or 2. it's part of a much bigger ship so the pod mass doesn't matter much.
If you can make it so your reentry vehicle is just a Mk1 pod trailing an (empty) SRB behind it, that should be easy with a shallow-arc trajectory: enter nose-first and use your command pod's torque to keep the nose pointed 20-30 degrees above prograde. This will generate lots of body lift and you should come in nice and easy.
Well, that's true. But you could lob it up high and keep a bit of fuel in reserve to slow yourself on the way down, just before hitting atmosphere.
I've never flown the Mk1-2 pod, only used it for the test. I unlocked it thinking it would be a better way to haul tourists around but then saw that I have no way to possibly use it at present--I don't have the 2.5m heat shield.
As for the SRB--I've always jettisoned it after the test. It doesn't have a shield, it's going to burn anyway. The reentry vehicle is a probe body, pod, crew cabin (tourist mission), service bay with power and a couple of light experiments and shield.
For my next attempt I'm going to try to put the periapsis into the atmosphere rather than the lithosphere.
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5 minutes ago, Snark said:
You should have no problem reentering from suborbital, with the right trajectory and ship design. It would help if you could post a screenshot so we could see what it looks like.
A couple of things:
First, if you're having heating problems for suborbital flights: what kind of trajectory are you using? Straight up and down? That can be problematic. Try launching on a long, shallow trajectory so that you go way far downrange; that way, during reentry you travel a farther distance through the thin upper regions of the atmosphere, and can shed more velocity there before you get down into the charbroil zone. Depending on the shape of your ship, you may also be able to leverage a trajectory like that to give body lift, which can seriously ease reentry if done right.
Second, regarding the parachutes burning off: Where are you putting them? Try moving them to where they're out of the airflow. For example, the Mk1 command pod has nicely sloped sides. If you're entering butt-first (i.e. with the command pod's pointy end pointing retrograde), put the chutes on the sloped sides of the command pod, not down on the cylindrical sides of the rest of the rocket. That way, they're out of the airflow and won't get heated so much.
Are you sure you have exactly the right part that you're supposed to be testing? For "test <specific decoupler> on the launch pad," all you should need would be the decoupler attached to a command pod. Launch, hit the stage button, you're done. What exactly does it tell you to test (the exact words in the contract), and what exactly is the part that you're testing?
(I note that there's no such thing as "Rockodyne". There's Kerbodyne, and there's Rockomax, those are two different things.)
Maybe the fact that I'm going up past 200km for the parts test is the problem then--there's no way to be all that shallow that way unless I carry almost enough fuel for orbit.
I am putting the chutes as high on the capsule as I can. I wouldn't expect them to survive on the sides where the ablator doesn't do any good.
And you're right--it's Rockomax. I'm getting check marks on the contract parameters, it certainly acts like I've got the right stuff.
Contract: Test Rockomax Brand Decoupler
The part I'm using is a Rockomax Brand Decoupler.
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27 minutes ago, PnDB said:
Hate to answer a question with questions, but...
Can you describe your rocket for the SRB test? What does your ascent profile look like (straight up to 200k and straight back down? a near-orbital-but-not-quite arc?) If you can get up to 200km in a graceful arc that puts your perapsis around 20-30km, you may reenter in a more friendly and less hot manner, losing sufficient speed in the upper atmosphere before you get too low and hot.
What does your separator "craft" look like? Is it just the separator sitting on the pad?
Test problem:
Mk1-2 capsule
Decoupler
2.5m service bay
There are two test conditions, both with what look like green checks (I have some red-green issues, while I'm sure the checks aren't red I won't swear they are green): Kerbin, Launch site.
However there is no Test button on the decoupler, just Decouple and Enable crossfeed. I've done parts tests with non-flyable contraptions before, it's always worked.
Parachute problem:
No, I am tipping over. IIRC I had several hundred m/s of horizontal velocity and topped out somewhere around 150km on my first run--successful. The second time the horizontal was something under 2000 m/s and I was falling back from something over 200km. I wasn't paying attention to perapsis as it was a suborbital flight anyway. The last time I'm sure my horizontal velocity was less as I tried going straight up until my apoapsis was like 210km and then discarding the booster. I then burnt the SRB pointing horizontally when I crossed the 200km point--it had over 900 m/s of delta-v. The re-entry vehicle is slightly heavier as I threw a thermometer and barometer in the service bay and I had a Probodododyne OKTO on the nose as I didn't have a pilot on board.
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8 minutes ago, fourfa said:
Welcome to KSP!
On solid rockets - you can adjust how much solid rocket fuel they get filled up with. By default, they are full to the max. But place one on your rocket in the VAB, right-click on it, and you can drag the Fuel slider back and forth to change the fuel load. In fact, you can turn it down to zero and the part test contract will still complete when you fire the (empty) SRB stage.
That should help on your suborbital velocity some. How to make your craft draggier is a longer topic - lots of people have this problem too.
On the separator contract - right-click on the part when you launch and go to the launch pad. You should see a Run Part Test button (or something like it) there.
That solves the part test contract but doesn't deal with the bigger problem of the chutes burning off. Note that the problem is not from popping them too early, they are being physically burned off the capsule long before safe deployment speed. I don't know if my capsule is draggy enough or not--I've reverted the flight when the chutes depart and haven't seen if it ever gets down to safe speed or not. The ablator seems to be protecting the capsule itself but the airflow past it is still getting to them.
As for the separator--I've had that before. It's not showing up in this case.
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I'm quite new to the game, so far I've only gone suborbital.
I'm trying to do two contracts at once--a tourist mission and a parts test. The parts test is leaving me with a lot of velocity (really now, why do they want me to test a solid booster at 200km up??) but still suborbital--and when I re-enter my chutes are burning off no matter how carefully I hold the tail into the fire. Obviously I could skip the parts test (I was able to bring the same hardware down minus a couple of bits of science and a lot of velocity earlier) but if I can't survive from high suborbital velocity how will I ever survive from orbit? Or is the problem that I'm carrying the ton of crew cabin?
Also, have I found a bug? I accepted a pad-test parts contract for a Rockodyne separator--and I can't find any way to do it. All the conditions are true but there's no test button and firing the decoupler doesn't fulfill it. Yes, it's 2.5m rather than 1.5 but I can build a 2.5m "rocket" (not that it could actually move) that should work.
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On 11/12/2015 at 9:45 AM, sebi.zzr said:
This mod was working great,until 1.0.4.Now when 1.0.5 is out,the only thing that works is auto data storage.The science is not auto colectable anymore.I have to run every experimet manualy.So i wonder are there any plans to update this?
Second this. I'm new to the game and so I haven't even tried it on older versions. There's no auto experiments happening.
output_log.txt has a bunch of the following error:
MissingMethodException: Method not found: 'ScienceData..ctor'.
at ForScience.ForScience.RunScience () [0x00000] in <filename unknown>:0
at ForScience.ForScience.Update () [0x00000] in <filename unknown>:0
I can't find anything at RunScience that should have a constructor to be missing. While I do speak C# I know nothing of trying to debug plug-in code beyond writing log lines. Is there any better answer?
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On 1/27/2014 at 8:51 PM, rdfox said:
Just go to www.astronautix.com and look up any ICBM of your choice. It'll have full stats, including thrust of each stage, TWR on each stage, and total delta-V, just like any other launch vehicle.
Bit of necromancy here: That site has no delta-v numbers on any ICBM I looked up. (I was interested in how far out an ICBM could go.)
Why did my rocket not launch???
in KSP1 Gameplay Questions and Tutorials
Posted
I guess I need to concentrate more on the top part of the tree. I was more interested in the stuff on the bottom that would get me more science. Why are the joints so weak? Don't Kerbels have good welding torches??