it tells that no valid position to teleport. is it intended? or banned by vanilla game?

2 things here:
1) I have been so busy with life, etc that I haven't had time to play with space age myself
2) I never intended the mod to allow teleporting between surfaces. That is even a bit too cheaty for me :)

I am going to release a new version soon (working out the nitty gritty as I write this) and will surely look into the issue. At the very least, I will include a graceful error message.

If you could post the entire error message, that would be most helpful.

Thanks for using the mod!

Thanks for your mod. I'm sorry if I bother your real life.

when I try to teleport to the space platform, "no valid teleport position found within the search radius. please select another position" is showed, and nothing is changed whether I enlarge the space platform or increase the search radius. but it seem not to imply that I can not teleport to other surface, as I succeed to teleport into the surface of factorissimo.

and finally, I agree that it's cheaty to teleport between surfaces. in fact, the reason I use this mod is that, I think that player sent by rocket must have empty inventory is just a punishment and waste of time (especially to the new players who don't know what next to do at all), so I attempt to get rid of this limitation.

Edit: oh I make a big empty area on the space platform and succeed to teleport onto it. though I don't know why, it works well for me now. and finally thanks for your mod.

Ahh, I think when you had the error it may have been telling you that there was no viable space to place a tag. For instance, you cannot place a tag atop a building (I think). So then it uses your search radius, which you can adjust in the player settings and I honestly haven't played with it much so I hope it works, to enlarge the radius from where you were trying to place your tag to find an open plot of land to place the tag.
You could try increasing that value if it's really crowded, or do what you did and place the tag in a more sparsely populated area.
Glad you like the mod!

You can't teleport to space platforms because they are not actually walkable. If you go there by rocket you are inside it and walking is not really walking. You do not see your character at all. If you use editor extensions while in the platform it will put you on the platform and you can walk around on it but then you can't get off at all unless you teleport off back to the planet. You cannot take the rocket back.

Use the rocket to get there.

From what I understanfd, this is not entirely correct and I will be adding a note to the README.md:

If you use this mod to teleport on a space platform and teleport to an invalid location (like empty space without tiles) which is entirely achievable when using a high value for search radius, it is entirely possible that the the player will fall and die! It is for this reason that I will be removing the mod functionality on space platforms in the near future.