Dracula 3000

In the year 3000, the space salvage ship Mother III happens upon the derelict transport Demeter. Captain Van Helsing (Casper Van Dien) and his crew board the abandoned ship.
They explore the bridge and find the corpse of the Demeter's captain, (Udo Kier) tied to a chair and clutching a crucifix. Despite the misgivings of crew, particularly intern Mina Murry (Alexandra Kamp) and vice-captain Aurora (Erika Eleniak), the Captain claims salvage rights and decides to tow the ship back to Earth. As the crew prepares to return, Mother III suddenly uncouples from the Demeter, leaving them stranded with no means of communication.
Later, cargo specialist 187 (Coolio) and deckhand Humvee (Tiny Lister) discover a cargo bay full of coffins. 187 speculates that the coffins could contain smuggled goods and opens one, only to find sand. Humvee heads back to the bridge while 187 stays to open the other coffins; he is soon mysteriously attacked. The crew rushes to 187's aid, only to find he is now a vampire. Under orders from his "master", 187 vows to kill the entire crew.
Aurora, fleeing 187, runs into the "master" (Langley Kirkwood), a vampire named Count Orlock. Aurora makes her way to a recreation room where she reports her encounter with Orlock and reveals his intentions to return to Earth. Upon questioning, she is unable to explain how she escaped Orlock unharmed.
Thinking Aurora could be lying, the Captain ties her up and Humvee guards her. Soon, 187 gains entrance and attacks Humvee, who manages to stake him in the heart with a pool cue. Aurora, still tied up, confesses that she is an undercover android cop investigating salvage activities. The Captain and Humvee feel betrayed, but untie her.
Searching the ship's database, the Captain and the Professor (Grant Swanby), who uses a wheelchair, discover that the legendary vampire hunter Abraham Van Helsing was one of the Captain's ancestors. The Professor believes Orlock will seek revenge against the Captain. The Captain learns how vampires can be stopped and decides to steer the Demeter on a course towards a binary star system.
The Captain and Aurora are soon confronted by Orlock. Aurora leaves to rally reinforcements, leaving the Captain to fight Orlock alone. Orlock eventually gains the upper hand and turns the Captain into a vampire. Aurora and Humvee return, only to be attacked by the Captain. Aurora stakes him with another cue stick, but Mina (now a vampire herself) attacks, allowing Orlock to escape. Mina is dispatched by Humvee.
The Professor, despairing of his chances of survival, finds Orlock, who promises to free him from his disability in return for aiding Orlock's return to Earth. When Aurora and Humvee return to the bridge, they find the Professor passed out. Aurora stabs him with a cross, revealing that he was a vampire. A furious Orlock tries to enter the bridge, but Humvee and Aurora close the door on him, cutting off his arm in the process.
As the Demeter draws closer towards one of the binary stars, Humvee and Aurora confess to each other that neither knows how to pilot the ship. Knowing they are about to die, they take comfort in the fact that Orlock's plan to return to Earth have been foiled. Aurora reveals that she is programmed for sexual pleasure, and it is implied the two spend their final moments having sex.
The movie ends with a video segment from the Demeter's Captain Varna, who announces his intention to sacrifice himself and his ship. The Demeter explodes in space, killing Humvee and Aurora, and destroying Orlock.

Question: Why does Orock seeks revenge against van Helsing ?
Answer: One of the ancestors of van Helsing is the famous vampire hunter Abraham van Helsing