Meithan

Ah, sorry about that. I did search for one but missed it. Will carry on the other thread. Mods are welcome to delete this thread.

A report by SpaceFlightNow suggets China's Chang'e 3 mission, which will take a robotic rover to the surface of the Moon (not to be confused with the Mun), might liftoff as early as next Sunday (Dec 1st): Chinese moon lander on the verge of launch China already successfully sent two lunar probes, and is now attempting a soft landing as part of its Moon exploration program. It's so nice to see new players (China, India) joining the space club. I opened this thread so we can follow up on this.

Thanks for the rundown, Jarnis. I feel bad for SpaceX, but to be honest they're doing things the right way. Definitely better be safe than sorry, and you can simply retry in a few days after all has been double- and triple-checked. What's a bit odd is that they've had 6 successful launch sequences with no issues so far (right? I didn't watch them all), and then suddenly two scrubbed ones. Well, it's true that out of those 6, five were Falcon 9 v1, not v1.1. Could it be something with v1.1? Also, didn't they do a static fire at least once before Monday's launch? That indicates that the engines were firing normally. Just bummer, I guess. But good call on aborting. And third's the charm .

Will watch. Hope they launch successfully today.

So, they will attempt launch today again, no?

Watching stream. Go SpaceX!

I'm so nervous about today's launch. But Elon Musk probably has it worse. From the SpaceFlightNow article:

Technically, the launch direction (called the launch azimuth, β) for a given desired orbital inclination i depends on latitude Õ as follows (according to the Orbiter wiki): From the equator (Õ=0), the launch direction is intuitively "the same" as the desired inclination. If you want a 30° prograde orbit, launch 30° north of east, which is equivalent to a launch azimuth of 60° (remember azimuth is measured clockwise from North=0°). But even this is assuming that (1) the launch is an impulsive maneuver that occurs instantaneously and (2) the planet isn't rotating. Of course, neither of these is true in practice. Point (2) can be factored in the calculation (see the Orbiter wiki article for the full details), but taking care of (1) would require a much more complicated trajectory planning that would depend on the parameters of the rocket and computer precision to execute it. An alternative approach is to use KER or MechJeb to have a readout of the orbital inclination as you launch. A formula like the above can give you a general idea of the launch direction. Then, as you climb, you can adjust your trajectory by looking at the real-time updates of the current orbital inclination. That's enough to generally get within a couple degrees of the intended orbit. Then you can do the final correction at the next ascending/descending node. By the way, I was investigating the efficiency of orbital inclination adjustment yesterday and I found out that for inclination changes below about 48°, doing the "increased apoapsis trick" is actually more expensive than doing the inclination change in your initial orbit. The trick is only good for large inclination changes, it seems. I'll make a post about it in the Science Labs subforum when I have some time to check the calculations and write it up.

Nice, thanks a lot for the trick. I'll put it to good use.

NJC2: Your orbit cleanup initiative is impressive for someone that just started playing KSP! In my opinion orbital rendezvous is one of the hardest skills to acquire when you're starting out. Kudos on achieving that. As for reducing inclination change delta-v, you can certainly do the "raise apoapsis" trick, but I felt like adding that the best way to save on delta-v is to launch directly into an orbit with the desired inclination (as somebody else already mentioned). You may lose the "free" delta-v from Kerbin's rotation (174 m/s), or even may be required to pay it (if you're launching west), but that's peanuts compared to the inclination change delta-v while in orbit (and it can be paid for by the launch rocket anyway, which lifts off the burden to your final spacecraft). Launching from the equator, you can reach any orbital inclination (including retrograde orbits) by simply pointing your rocket in that direction when starting the gravity turn (well, approximately at least; Kerbin's rotation will alter the final result a bit). The higher the apoapsis, the more the delta-v saving. Push it all the way to the limits of Kerbin's SOI (~80,000 km) if you want the minimal delta-v requirement and don't mind timewarping a lot (and having to be careful to avoid encounters with the moons). Yup, even factoring in the cost of raising the apoapsis that high, you'll end up saving delta-v in the end. It may be counterintuitive, but it's due to one thing (which is the lesson to be learned here, I suppose): inclination change maneuvers are very darn expensive! One thing to note, though, is that you get diminishing returns (in delta-v saving) as you raise the apoapsis more and more. The difference in delta-v saved between using a 4000 km apoapsis and a 80,000 km apoapsis is less than 200 m/s. Probably not worth it. What you did (raising the apoapsis to ~ keosynchronous altitude) was probably pretty efficient.

Nope, that's not correct. You can save delta-v by doing the inclination change at a higher altitude, even including the delta-v spent in the two burns required to first raise and then lower back the apoapsis, and without aerobraking. Here's an example with numbers. Suppose we're in a 80 km circular orbit around Kerbin, and we want to change our inclination by 90°. We have two options. Option A: perform the inclination change without changing orbit Computing the required delta-v is straightforward here. Delta-v required: 3223 m/s Option B: raise our apoapsis, do the plane change, then lower the apoapsis back to 80 km Here we have to calculate the delta-v in three steps. 1) First, raise the apoapsis to, say, 1000 km altitude. Delta-v for ap increase: 421 m/s 2) Perform the inclination change at new apoapsis (1000 km) Delta-v for inclination change: 1623 m/s (quite a lot less!) 3) Burn at periapsis to circularize back to 80 km Delta-v for circularization: 421 m/s (the same as the first, of course) The end result is the same. Total delta-v required: 2465 m/s That's a sizeable saving! And the more you raise the apoapsis, the larger the saving (although you start getting diminishing returns as you increase the apoapsis more and more). With aerobraking you can cut down on that third delta-v too.

This may be a noob question. I'm currently developing a plugin and it's a pain to have to exit the game and reload whenever I change the plugin's code. Is there a way to make the game reload the plugin without reloading the whole game?

Apparently, launch profiles that use a super-synchronous orbit in order to reduce inclination change delta-v and thus require several rocket restarts are utilized by the Proton M launch system (which launches from Baikonur Cosmodrome, at 46°N latitude), so they're not that uncommon. From Wikipedia:

From the SpaceFlight101 article: Remember it's cheaper to change inclination when you're moving slowly, i.e., at high altitude.

Well, that's easy: he'd want a delivery orbit with a period as close to 4.5 hours as possible. I just think it's easier to read the periapsis/apoapsis distances directly from the game than figuring out the period from the "time to periapsis" and "time to apoapsis".

I don't know about MOM specifically, but spacecraft usually take color pictures by taking separate pictures through different color filters. The pictures are then sent back individually and they have to be combined during post-processing to produce a color image. This is usually not a trivial process, as they have to be aligned, balanced, etc. Pictures of Earth taken recently by the Juno spacecraft as it flew by on its way to Jupiter are an example of this.

I crunched the numbers for you. In fact, it's cheaper that you shoot for a "delivery orbit" with a period that is 25% smaller instead of larger. An orbit with a period of 4.5 hours (16200 seconds) that has its apoapsis at the keosynchronous altitude (2868.6 km) would have a periapsis altitude of 1658.0 km. The process is then as you described: you release a probe at apoapsis, have it circularize its orbit, then wait one orbit (4.5 hours) and when you're back at apoapsis you release the second probe, circularize its orbit, and so on. You'll get four nearly equally spaced probes.

You can use the expression for the orbital period I gave before and the fact that the semi-major axis is the average of periapsis and apoapsis to solve for the apoapsis if the period and periapsis are fixed. Rearranging the aforementioned expression for orbital period, you can write Then, use the fact that to solve for the apoapsis distance. You'll arrive at: where T is the orbital period that you want and rpe is the periapsis distance. By the way, you might want to look at this thread, in which I showed an arrangement of keosynchronous satellites very similar to what you're planning to do. Edit: and if you want to know more about the details, check out my mission log.

While that's true, if the average of the altitudes is the same, then so is the average of the distances to the center of the planet. That is, we can determine whether two orbits have the same period by comparing their periapsis/apoapsis altitudes. I think it was just a miscalculation on his part.

That formula's correct (and by the way, it's pretty much Kepler's Third Law). The period of a small body in orbit about a central body of mass M depends directly on the length of the semi-major axis a of the small body's orbit: As you guessed, that means it's possible to have a circular orbit that has the same period as an elliptic one, although your example wasn't quite correct (remember that semi-major axis is just the average of the periapsis and apoapsis distances). A circular orbit at 250 km altitude above Kerbin's surface would have the same period (43m 44s) as a 150 km x 350 km elliptic orbit (since its semi-major axis is the same). Notice that for that to work, the periapsis must be lower than 250 km while the apoapsis higher than that. If the elliptic orbit is completely below or above the circular one, they will have different periods.

Wow, TechSupport, I'm wordless! That's a beautiful shot of our world. May we share it in peace!

Ah, nice, I wasn't quite aware of that.

We're just waiting for MAVEN to phone home now. After that, we can sit back and relax.

Spacecraft separated! Applauses in the control room! Maven is cruising on its own towards Mars. Congratulations to the team!

Two minutes to spacecraft separation.