I hot keyed Radaway and was able to make it to the door (which was inaccessible) and still didn't get credit for discovering it... what gives?

when you go through the main quest you will go to vault 87, but if you want to discover it by stepping the front door, its impossible, the rads will kill you outright, you can try a lot of things (like i did) but i never succeeded (or honestly, bothered) so if you have the game on pc you can have mods that could give you a good anti rad suit. Otherwise that is all there is.

Yes, but even after the main quest is complete, Vault 87 still shows up as an undiscovered location on your world map. I made it to the wooden Vault door (where a new Vault location discovery is usually announced) but you couldn't get in as it is "inaccessible". However, I would think that having made it there the "discover" flash with a customary 10 points of XP would have shown up.

actually when i used a mod to see if i could discover vault 87 (you mean stepping in the front door, the indication of 'you discovered vault 87' will show, and you will receive xp?) yes that happened to me. I received xp and in my pipboy the location of vault 87 (with a fast travel option) showed.

you did approach the vault 87 door from the outside right? if yes that is the proper way to do and the 10 exp should show, otherwise we could blame it on bugs, be sure that you patched the latest software on your fo3 game.

Either that, if still not successful, try to load the nearest save where you can try to access vault 87.

Hope this helps.

It is discovered in one of my games. I'm on an Xbox 360.

Holy crap did I burn through my RadAways though. Got there, added it to the map, tried fast traveling out... bad idea.

if i remember it right (since its a year when i last played fo3) you cant fast travel when exposed to radiation (err, correct me if i'm wrong).

I have it discovered on my 360 too. I just spammed RadAway and Rad-X.

It's not that hard to do. I did it multiple times when I played Fallout 3. Just Hot Key Radaway and you'll be fine. You don't even have to reach the door. It's best to do it before you're level 30 though. The EXP "ca ching" will let you know when you're done. Then just fast travel out of there. It might take a couple of tries, but it's not impossible at all.

You have to go through Little Lamplight because Vault 87's door was directly hit by a nuke (for some reason the radiation never faded)

Once you get into Little Lamplight go through Murder Pass and tada you're in Vault 87

He doesn't want to get in, he want's to be right outside the main vault door, so he can "discover" it. It gets marked on the map, and you can fast-travel there directly. (Although it's suicidal)

That's what I did.