Alvin is a small submarine that has made many breakthrough discoveries over the last 40 years:

But Alvin has two problems: 1) it is 40 years old, and 2) it can’t go any deeper than 2.8 miles.

In this video you can see them disassembling Alvin during a 2005 overhaul. At about the 1:00 minute point they expose the pressure sphere that houses the human beings. This sphere is the source of the 2.8 mile limit:

To create a better vehicle, they need a better sphere, and that is what this article is about:

New Sphere in Exploring the Abyss

The new sphere will be made of titanium and it will have walls three inches thick. The two year prcess will create one of the largest, strongest titanium objects in existence. According to the article:

Alvin can transport a pilot and two scientists down 2.8 miles, providing access to 62 percent of the dark seabed. The new vehicle is expected to descend more than four miles, opening 99 percent of the ocean floor to inquiry. But the greater depth means that the vehicle’s personnel sphere and its many other systems will face added tons of crushing pressure.

See also: How DEPTHX Works