why do they have to use a rocket to get to the space station, couldn't they use a sort of plane by now.?

There have been planes built as far back as the 1970s that have taken the pilot to the edge of the credible atmosphere, and a few years ago another aircraft was designed that can carry six passengers to an altitude much higher than what the space shuttle can attain. During the flight, the passengers would be weightless for 5-10 minutes. Last I heard, the company designing this craft was trying to sell passenger tickets for $200,000. However, neither this plane nor any of the earlier versions would never achieve orbit. They would simply go up to their maximum altitude, and head right back down and land. They would not be able to lift nearly enough fuel to attain orbit.

Well first off the plane's wings still needs an atmosphere to be useful. And in orbit there is no atmosphere.

The wings on a space shuttle were used to slow the space shuttle down during reentry and glides itself back down.

But even the space shuttle still needed rockets to achieve the orbit speed needed to catch up to the space station. Simple jet engines can't cut it right now, especially with no oxygen in space. Even if they carried their oxygen, they still need lots of fuel, meaning lots of oxygen, and both seriously weighs down the ship.

Rockets are better equipped to handle the high heat for getting to and from space. Planes, since they have to be so light to get thrust, can't handle the weight of the outerskin of a rocket that protects is from the heat and besides, jets are faster than planes. Rockets are also faster since they have boosters. They can hit Mach 3.2 much faster than a fighter jet.

Even if you had a rocket plane the power needed to get the plane to the same altitude as the rocket is more because some of the power is wasted on tangential motion thats motion along the ground.

Nope. The usable atmosphere only goes so high; planes can get up really high - about 120,000 feet in one case - but... That's a little short of the 1,584,000 feet that the space station orbits at...

So, they need rockets.

In addition to all of the reasons already mentioned "a sort of plane" cannot be used to reach the ISS, consider the following:

The average orbital velocity of the International Space Station is 7.66 km/s. That's 27,576 kph or 17,235 mph. The lowest point in its orbit (perigee) is 409 km (254 mi). The highest point in its orbit (apogee) is 416 km (258 mi).

To stay in orbit, the ISS has to travel over 27,000 mph. This is much faster that any plane has managed, even the US Blackbird was "only" about 7,000 mph. This is why the Shuttle, which was a sort of plane, needed the solid rocket boosters and the on-board rocket to boost it up to the ISS velocity.

A space shuttle sort of is a sort of plane. But an airplane cannot fly into outer space. It takes a considerable amount of rocket power to escape the earths atmosphere and a normal jet is not capable of that.

As other have already said, aircraft are made to fly in the air, hence then name. Maybe instead of "a sort of plane" you meant to say single-stage-to-orbit vehicle. We tried that, but the project was cancelled when it became clear that we didn't possess the technology to make it truly viable, and that the vehicle could barely lift a stripped-down version of itself into orbit, never mind a useful payload.

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To get into orbit a massive amount of energy, although there are designs of small planes that launch of bigger planes rockets are the fail safe way of getting into space.