Relationships will once again be the underlying theme on "The Big Bang Theory" this week as Howard will attempt to mend his cantankerous relationship with Sheldon.

In the upcoming episode, "The Friendship Turbulence," Howard Wolowitz will invite Sheldon to travel to Houston with him in an effort to improve their friendship after a recent spat. While it's unclear whether or not their friendship will improve, a promo video shows that the two will use air sickness bags in a very unique way during their flight.

CarterMatt offers more insight about their quarrelsome relationship, which has been building since almost the beginning of the series. Unlike Sheldon, Raj, and Leonard, Howard has been the outsider in the group because he doesn't have a Ph.D, and Sheldon never hesitates to remind him. However, he is granted the once-in-a-lifetime chance to go to space. As a result, Sheldon is jealous, even if he does not admit it.

According to Hollywood Hills, the official synopsis reads: "After the insults fly, Bernadette tries to broker the peace between Wolowitz and Sheldon. Meanwhile, Penny is offered an embarrassing movie role and Raj asks Amy to write to a woman on his behalf."

Still photos for "The Friendship Turbulence" reveal insight into Raj and Amy's storyline for the episode where Amy will be playing the role of Cyrano de Bergerac in Raj's latest romantic theatrics, reports Hypable.

The stills also provide a quick glimpse at Penny and Leonard's latest adventures, revealing that whatever Penny's "embarrassing movie role" turns out to be, Leonard will not be in favor of it.

The Big Bang Theory S7E17, "The Friendship Turbulence," will air on Thursday, March 6 at 8 p.m. EST on CBS.

Watch a preview below.