Padacke served as prime minister from 2016 to 2018 and was seen as an ally of Deby, who ruled Chad for 30 years.
A military council seized power after Deby was killed as he visited troops fighting rebels on April 19.
Opposition politicians have called the military takeover a coup, and two said on Monday the army had no right to pick a premier.
The transition and the wrangling around it is being closely watched in a country that is a power in central Africa and a longtime Western ally against Islamist militants across the Sahel.
The military council is headed by Deby’s son, Mahamat Idriss Deby, and has said it will oversee an 18-month transition to elections.
Mahamat Idriss Deby, a general bon on 1 January 1984, has been declared the national president and has dissolved parliament.
But the council is coming under international pressure to hand over power to civilians as soon as possible.
The African Union has expressed “grave concern” about the military takeover, while France, the former colonial ruler, and some of Chad’s neighbours are pushing for a civilian-military solution. read more
The U.S. State Department said the naming of a civilian prime minister is “potentially a positive first step in restoring civilian governance,” adding that Washington is continuing to closely monitor the situation.
“We would urge that this moment be taken to move the country forward in a democratic direction and that the people have an opportunity to really have a democracy, have a representative government,” Robert Godec, acting assistant secretary of the State Department’s Bureau of African Affairs, told reporters.