Orbiting

[Kevin W.]

I'm still working on getting my orbits down. I'm having some issues. I've finally gotten the mechanics down. I know how to reorient myself at 10KM and doing the gravity turn and getting the apoapsis above 70KM, but I'm running into a problem on my orbital burn. In my attempts to boost my probe up to a high-enough altitude so its periapsis is above 70KM to establish a permanent orbit, my probe keeps flying into an escape trajectory. Obviously, I don't want to do that. What's going on?

Also, while it's not affecting the rocket so much as to render it incapable of achieving orbit, my probe launcher does wobble quite a bit during launch. Is it the height causing that? If so, is there a way to fix it besides making the rocket shorter?

Edited July 14, 2013 by Kevin W.

[SPWeber]

You need to burn at apoapsis otherwise it will continue to rise away from you to the point that it escapes the planet.

[halrick]

Raise apoapsis to desired level -> cut engines -> just before reaching ap, fire engines toward prograde to bring pe up to desired level. You'll, ideally, want to burn 50% of the circularization burn before reaching ap and 50% after; i.e. for a 20 sec burn, don't wait to reach t-0 at maneuver node but rather start burning at t-10. To get a better feeling for all things orbital maneuvers, burn pro- and retrograde at both ap and pe and see how they influence the orbit (when a stable orbit is reached)

[stupid_chris]

Hmm for the wobble we would need pictures to have a better look at it, depending on how you structured it, it could be your problem. Usually a few struts to hold things together. But to tell precisely, we'd need screenies really.

And yes, to raise your periapsis without getting on an escape trajectory, you want to burn prograde, but you want to burn prograde the closest possible to your apoapsis. You have to be careful, if you burn after, you're gonna start going back down again and you might reenter the atmosphere, and you don't really want this.

[Nibb31]

You need to burn on the opposite side of the orbit that you want to change. Burn at Pe to raise or lower the Ap, burn at Ap to change the Pe. And of course, you burn prograde (accelerate) to raise your orbit (which will have the effect of making you go slower) and burn retrograde (slow down) to go lower and faster.

It's all a bit counter-intuitive really, but once you understand what's happening, it becomes quite clear.

[LeFudge]

You might be burning too hard too early, when my Apoapsis gets about 1m30s to 2mins away(and above 80km) I shut down my thrusters and wait to catch up to it before continuing to burn.

[Kevin W.]

Well, easier said than done considering my launcher is an uncontrollable mess that can't seem to make a minor course correction without going into an uncontrollable spin. How do I make it stop when I'm making the course corrections?

[stupid_chris]

We're definitely going to need screenshots of your launcher. It'S probably not stable enough. Struts goes, but really a screenshot would be awesome.

[Kevin W.]

Alright, I'll get a screenshot tomorrow. Just a fair word of warning: it's going to be ugly.

[KerbMav]

There is no ugly, only interesting!

Check if CoM and CoT of your upper stage(s) are lined up nicely and you dont burn your fuel in a way that imbalances the ship over time.

[Vanamonde]

It takes around 2000m/s to get from the pad to orbit, but after that, a small change in speed will make a big difference in orbit. The difference between a low orbit and a high one is just a few dozen m/s, so a common new pilot mistake is to simply keep burning hard a little too long. Watch on map view, and as you get close to orbit, simply throttle back so that you don't overshoot.

[Kevin W.]

The launcher uses some welded fuel tanks from UbioZur.

This is a modified design from what I was working on last night. Now, instead of wobbling, it tips over while the first stage is firing.

Edited July 14, 2013 by Kevin W.

[stupid_chris]

Well first, canards at the bottom won't work, they're made to go at the front of a craft. AR8 winglets (I think it's their name) works best for rockets.

Second, that bottom connection tricoupler to tricoupler sounds like a wobble wagon. Might want to strut that. Then on your last stage, switching the LV-T45 for an LV909 would probably be more efficient for the whole launch vehicule, you're cutting 1t out of the payload.

Lastly... why so many probe cores for that satellite?

Edit: also, on such a light satellite (and with that much probe cores) you won't be needing RCS at all. Trust me lol, that thing is too powerful for such a small payload.

[Nibb31]

First get rid of those triple tanks and tricouplers. They mess up your fuel flow, and they cannot connect properly on the bottom due to the single parent-multiple children hierarchy structure of KSP rockets. Instead, use single tanks.

Also remember that your first stage needs to have at least three time the thrust and weight of your second stage. If your rocket has identical first and second stages, then you are doing something wrong. Either your first stage is too small, or your second stage is too heavy.

Finally, as already stated, do not use canards below the center of mass, they tilt in the opposite direction to winglets. Also anglers are only really useful at low altitudes. But if you are using them to correct stability problems at low altitudes, then something is wrong with your rocket.

[Kevin W.]

Holy crap, that may be the solution to my problems. I've been using canards this whole time. Thanks for the clarifications.

[NASI Director]

Also, while it's not affecting the rocket so much as to render it incapable of achieving orbit, my probe launcher does wobble quite a bit during launch. Is it the height causing that? If so, is there a way to fix it besides making the rocket shorter?

Struts, definitely struts.

[stupid_chris]

Holy crap, that may be the solution to my problems. I've been using canards this whole time. Thanks for the clarifications.

Also, instead of using those combined parts, some 2m tanks would probably do a better job.

And Nibb, he's using fused parts from a mod, they don'T have the fuel flow problem. The whole three FT-800 tanks and the two tricouplers are one part.

[Kevin W.]

OK, so I need to make changes to the probe, switch the canards out for winglets and add more thrust to the first stage. Am I missing anything?

[Kevin W.]

Here's the new launcher. I'm at my wit's end here. I'm angling the rocket at 10KM and once the apoapsis is at 70KM, I cut the engines to just float up to it. However, every single time I try to course correct to a horizontal heading to burn when I'm at apoapsis, two things happen: it takes too long to turn the rocket so I miss the apoapsis and start my burn after it, since for some reason pressing shift in the orbit mode doesn't throttle up and the rocket ends up over-rotating and it goes into an uncontrollable spin. Why am I having so much trouble? I know this game isn't just a point-and-click space simulator but why does it have to be this freakin' difficult to do a simple task?

[Nabiscovinco]

Well an uncontrollable launcher is bad, but what I always do is use the maneuver nodes to make orbits; Noobish? Maybe, but it works.

[Kevin W.]

Basically I get the feeling that I'm going to have to spend the whole time micro-managing the WASD keys. That's just fantastic, knowing that the slightest tap of one of them causes the rocket to start spinning uncontrollably.

[Nabiscovinco]

Have you tried ASAS or SAS? They keep it from... not flipping over. And stupid (lawlz, stupid... I digress) is right. If you think realistically, a much MUCH smaller rocket can be used to put a small probe in orbit.

However, on the first stage, get rid of the two tri-couplers and just attach the engines directly to the fuel tanks.

[Kevin W.]

The upper tri-coupler is part of the part. It's a welded part by UbioZur: http://forum.kerbalspaceprogram.com/showthread.php/38577-0-20-UbioZur-Welding-Ltd-Lower-your-part-count

Also, I do have ASAS and SAS on the rocket, but pressing the WASD keys does absolutely nothing when SAS is on, and if I turn it off and then try to make a course correction, the uncontrollable spinning happens.

[Johnno]

However, every single time I try to course correct to a horizontal heading to burn when I'm at apoapsis, two things happen: it takes too long to turn the rocket so I miss the apoapsis and start my burn after it, since for some reason pressing shift in the orbit mode doesn't throttle up and the rocket ends up over-rotating and it goes into an uncontrollable spin.

Instead of waiting to reach 70km to turn for your burn, do so beforehand. Most often I have to turn off my engines around 40km or so and coasting up takes over a minute, giving plenty of time to both set a manouver node and point the nose on the horizon. Or other way around, whichever I feel for at the time. And if the rocket isn't responsive enough, either RCS or turn on the main engines on low power for a gimbal assisted turn.

And orbit mode? Oh you mean mapmode? You have to toggle your navball up onto your screen for your controls to work. You can manouver and burn in mapmode as long as you have the navball up.

Why am I having so much trouble? I know this game isn't just a point-and-click space simulator but why does it have to be this freakin' difficult to do a simple task?

Sounds to me like you're rushing things. Your launcher looks really overengineered for what it's supposed to do. I'm a big fan of overengineering, but your launcher is over the top. Learn with smaller and lighter stuff. Start with just one T800 tank and a LVT45 engine. Launch, see how it behaves, pitch it toward the horizon, check mapmode, set some manouver nodes, crash it into the ocean. Add another tank and rinse repeat. Add winglets, rinse repeat. You've built a complex and quite large rocket without first learning the basics, so my advice would be to go back to the beginning.

Spaceflight is hard. And even though KSP isn't fully realistic, it's realistic enough that as you say, it's not just point and click. If you don't know how to fly rockets, you have to learn. Looking at your screenshot, I think you've skipped a lot of steps.

I myself didn't watch any tutorial videos or read up online, sure I have a background in space science but even then there's a steep learning curve. Unless you go through each point necessary you will end up frustrated and hit a wall. I don't think anyone could get into orbit on their first few rockets, and once they did those orbits weren't pretty.

Start from the beginning, one step at a time, learn as you go.

[Ohfive30]

Here's the new launcher. I'm at my wit's end here. I'm angling the rocket at 10KM and once the apoapsis is at 70KM, I cut the engines to just float up to it. However, every single time I try to course correct to a horizontal heading to burn when I'm at apoapsis, two things happen: it takes too long to turn the rocket so I miss the apoapsis and start my burn after it, since for some reason pressing shift in the orbit mode doesn't throttle up and the rocket ends up over-rotating and it goes into an uncontrollable spin. Why am I having so much trouble? I know this game isn't just a point-and-click space simulator but why does it have to be this freakin' difficult to do a simple task?

Your rocket looks quite cool, but one thing i would say is that looks like a big rocket for a small payload, particularly if you're only going into kerbin orbit.

For getting your orbit sorted out, as soon as you cut your engines to coast to the Apoapsis, go to the map mode and add a maneuver node, then you can have plenty of time to turn the ship and point in the right direction prior to the orbital burn.