Gravion

The year is now 2041 AD. A new enemy called Zeravire suddenly appears in the solar system, destroying all military installations it comes across. However, a wealthy man named Klein Sandman is already aware of this planned invasion and had been secretly preparing his army for battle. His trump card is Gravion, a giant robot that utilizes gravity as its source of energy. Meanwhile a young man named Eiji secretly enters Sandman's base in search for his missing sister. (myanimelist.net)