Radial In

Radial in is basically anti normal, but horizontally in your orbit. Radial in is like, pointing inside your orbit. Think of a closed line, a good example would be in string theory. The craft is on the line, and points in the center of it, that’s pretty much radial in. But how do you use it and what it it good for? Well radial in is (in my opinion from what I’ve experienced) useful for changing your orbit’s eccentricity while anti normal changes the inclination, it can also largely change the arg of periapsis when you do a radial in burn at the right time, so be careful.

Radial Out

Radial out is pretty much radial in, but it is inverted. In Kerbal Space Program there is a tutorial that states “radial out basically points you up”, but that isn’t necessarily true unless you’re in surface mode. But for SimpleRockets 2 in surface mode there is literally a button for pointing up. Radial out is very handy when changing your orbit when your about to crash, but remember to point prograde when you attempt to avoid entering the atmosphere to do an unplanned aero break or something.

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    4,712 sacr3dbac0n0

    For working in circular or low eccentricity orbits, radial in/out does not get much use. It is useful when trying to adjust an intercept with a target closer while in similar orbits.

    However, radial in/out is important for working with hyperbolic trajectories, and beyond, like brachistochrones. In other words, at relatively high velocities, it is most effective to burn radial in/out to adjust your course (adjust your closest approach to an object) rather than prograde or retrograde.

    Pinned 3.1 years ago
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    @FriendlyFin
    Hey, just wanted to let you know I've come up with something very interesting and it was inspired in part from this discussion 😉

    If you want to check it out and give it a go it's here: ![](https://www.simplerockets.com/c/J94xv5/Virtual-Instructor-Edition-GTO-Get-To-Orbit-V-3-uM).

    3.1 years ago
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    @AverageJoe

    no comment

    3.1 years ago
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    @FriendlyFin I've noticed that game and have always been hesitant to hit the buy and download button. I'm a fan of realistic, and that just seems a little "out there" ( no pun intended 🤣) it's on the radar but not the nearby radar for now lol

    3.1 years ago
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    @AverageJoe
    you should try space engineers it’s next to impossible to orbit because the maximum speed to fly is 110 m/s, but with an unlimited speed mod, orbiting will be easier but the soi of all the planets and moons are incredibly tiny, i estimate 30 km from the surface to space by default. also there is no map that displays your orbit, also the planets don’t move and are impossible to move, and the atmospheres look really tall, making it look stupid. but there are clouds and other things that look beautiful and they slowly move, but they are also very high among the surface. i have attempted an orbit but it was meant to plummet into the atmosphere and land somewhere else on earth (like), so it wasn’t a complete orbit around the planet but i am certain orbiting is possible with unlimited speed mods

    3.1 years ago
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    @FriendlyFin sorry just getting started with the forum. I've thought of actually making some guides for new players on how to get into orbit and manage a few things, but I have most of my experience in KSP so I need to get some space time with SR2 in so I can speak in SR2 terms and not Kerbal terms 🙈🤣 translation of math is all lol

    3.1 years ago
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    @AverageJoe
    Why didn’t you put all that in a separate forum…

    3.1 years ago
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    Sorry if I can do this a different way, first time in the forum and things aren't coming all at once. Some final thoughts on the radial out and in, is when it comes to trajectory adjustment on landings. If you overshoot, but have a good speed you don't want to change, radial in acan shorten the trajectory, and radial out will lengthen if you undershoot. It's a little more advanced in maneuvering, but it will not require wasted delta v by drastically affecting your speed, an is also much faster at rotations to the marks, which is better for keeping the power to the ground direction with last minute adjustment. Normal and anti normal also become involved at this point, because they will do the same for left and right adjustment without affecting your speed much as well. If you do your entry angle burn right, chances are pretty good you have the right speed and are about 20km off target, so these menuvers in this situation help make major adjustment without using high amounts of delta v, or changing your speed requiring more delta v and more adjustment because you slowed down for overshooting and now your under🙈.

    3.1 years ago
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    Some expansion on the radial out and radial in.

    If you are halfway between the periapsis and apoapsis, a full radial in will raise your periapsis and lower your apoapsis, retrograde direction burn will maintain the periapsis but lower the apoapsis in this situation. The opposite is true with radial out in this situation. You can radial out and raise the apoapsis but lower the periapsis, retrograde direction burning will maintain the periapsis.

    If your between apoapsis and periapsis, everything I just said is flipped. Radial in will lower the periapsis and raise the apoapsis, prograde direction burn will maintain the apoapsis, and radial out will raise your periapsis and lower the apoapsis. Prograde burn direction maintains the apoapsis.

    The best way to explain it is like a ceterfuge or cetrifical force. The closer you are to the center, the faster you go. Each gravitational field is round, and therefore nothing but a sling shot. To slow down/ go lower, get further from the center, to speed up/ get higher, get closer. I hope it's not too confusing, and I hope I didn't mixit all up 🙈, but that's the most I've understood about radial out and in pertaining to landing, escape angles, getting to orbit, not crashing because somehow your periapsis passes through a moon mountain, and so on. Sometimes a small adjustment just won't cut it, that's where radial out and in shines.

    3.1 years ago
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    One use I've recently found for radial out/in maneuvering is in very low or at sub orbital levels. It tends to help the best halfway between apoapsis and periapsis, but you can greatly affect your upcoming node while maintaining your previous node and make major adjustment. Only downside is it takes about 20% more delta v over doing burns at a node.

    Example, you launch slow, get into sub orbit low and don't quite have the speed to raise a complete orbit before you pass your apoapsis. Common without enough twr starting off the pad. You already have a high enough apoapsis or maybe it's as low, but don't want it at 200k meters before you make it to an orbit, so to correct the situation and maintain say a 90km node(apoapsis or periapsis) you pitch 45 degrees to radial out or if it's really bad full radial out. Then by pitching between full radial out and less than full (all prograde direction burning) you can essentially maintain the past point or raise it more if close to it, and drastically change the periapsis to make an orbit and not dip in and out of the atmosphere wasting delta v just getting up there, or having a massive apoapsis you now have to retro burn to bring back down.

    By using the radial in, in a retrograde direction, it will bring the coming apoapsis down, but not affect the periapsis, like if you were to be aerobraking, and have a little more left to bleed off, plenty of delta v, and no more atmosphere until you come around again, you can use this type of radial in retrograde burn to keep your periapsis but lower your apoapsis down more. These menuvers have the greatest effects at halfway between between Ap and Pe, but will work the same closer to these nodes, but with lesser effect to the furthest node the further from between the two you are.

    Little difficult to explain on paper, but a quick try while watching your ap and pe as you do the burns and it will make sense.

    3.1 years ago

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