He'll tell you that your dad went to rivet city to end this quest, and start the next one on the list. With the dish attached, fast travel to GNR plaza and go speak to three dog. 400 feet up ! (hope you aren't afraid of heights !) Just walk over to the relay box and activate it. Now you need to head over to the Washington monument and take the elevator to the top floor. Just jump off the balcony down to the lander take the transmitter dish. You'll have to pass through the vault tour first, then you'll need to go through the room that has the Delta II rocket once you're in the room with the big lander like thing. When you're inside, go left and up the stairs. Once you finally come out in the mall, you'll need to follow you're map marker to the museum of technology. Eventually, you'll come out at Dupont circle and you'll have to go back into the Metro. just look for the signs that say Mall outpost, with little arrow above it. Now you'll be in the maintenance tunnels which lead to Dupont circle. Once inside, turn a little to the left and go straight.

There should be a door to the left of the wall at the opposite end of where you exited GNR, this leads to the collapsed car tunnel. Head out the back door of GNR and jump down the ledges and go right. Talk to three dog about dad and he'll tell you about how he needs you to get him the satellite from the virgo 2 lunar lander which will end this Quest. Once inside, Go upstairs and head into the Studio on the third floor. Talk to Sentinel Lyons about getting in to see Three Dog and she'll give you clearance. You also will want to search the different body's of the dead B.O.S soldiers, one which has a Fat Man and eight Mini-Nukes. Go and loot all the weapons and ammo from it's corpse before it disappears. See why you needed to stay in the building ? Shoot the Behemoth from a safe distance until it's dead. When they do, a huge Super Mutant Behemoth will come rampaging into the courtyard. But before you go into the courtyard, Let the rest of the Lyons pride go ahead of you.

You'll need to follow the Lyons pride to the GNR courtyard after killing off a couple of super mutants. Now you've got to head out into the wastes and look for GNR studios,(it's a good thing you have a map huh ?) when you finally reach the Lyons Pride Brotherhood of Steel squad talk to Sentinel Lyons about helping fight super mutants. If you give him one hundred caps, he'll tell you where dad went which will start your next Quest.

The first thing you need to do is to head into the saloon and talk to Colin Moriarty about dad.

You're gunna want to head towards the marker on your map and go to the town of megaton. Now that you've finally gotten out of that vault you can do what ever you want, Sort of.

Fallout 3 how to get to gnr