John Leonard "Jack" Swigert Jr. (August 30, 1931 – December 27, 1982) was an American test pilot, mechanical and aerospace engineer, United States Air Force pilot, and NASA astronaut, one of the 24 people who have flown to the Moon.
Fred Wallace Haise Jr. ( ; born November 14, 1933) is an American former NASA astronaut, fighter pilot with the U.S. Marine Corps and the U.S. Air Force and test pilot.
 He is one of only 24 people to have flown to the Moon, having flown as Lunar Module Pilot on Apollo 13.
 He was to have been the sixth person to land and walk on the Moon, but the Apollo 13 mission was aborted before lunar landing.
 He went on to fly Space Shuttle Approach and Landing Tests in 1977, and retired from NASA in 1979.
Lee Joseph "Bru" Archambault (born August 25, 1960) is an American test pilot and former NASA astronaut.
 He has logged over 4,250 flight hours in more than 30 different aircraft.
 Archambault is married with three children.
 His hobbies include bicycling, weightlifting, and playing ice hockey.
 Archambault has received numerous awards and honors throughout his life.
 He has also flown two Space Shuttle missions, as pilot of STS-117 in 2007 and as commander of STS-119 in 2009.
 Archambault left NASA in 2013 after a 15-year career with the agency in order to become a test pilot for Sierra Nevada Corporation on their Dream Chaser orbital spaceplane project.
Alan LaVern Bean (born March 15, 1932), (CAPT, USN, Ret.)
, is an American former naval officer and Naval Aviator, aeronautical engineer, test pilot, and NASA astronaut; he was the fourth person to walk on the Moon.
 He was selected to become an astronaut by NASA in 1963 as part of Astronaut Group 3.
 He made his first flight into space aboard Apollo 12, the second manned mission to land on the Moon, at the age of thirty-seven years in November 1969.
 He made his second and final flight into space on the Skylab 3 mission in 1973, the second manned mission to the Skylab space station.
 After retiring from the United States Navy in 1975 and NASA in 1981, he pursued his interest in painting, depicting various space-related scenes and documenting his own experiences in space as well as that of his fellow Apollo program astronauts.
"Houston, we have a problem" is a popular but erroneous quote from the radio communications between the Apollo 13 astronaut Jack Swigert and the NASA Mission Control Center ("Houston") during the Apollo 13 spaceflight, as the astronauts communicated their discovery of the explosion that crippled their spacecraft.
 The erroneous wording was popularized by the 1995 film "Apollo 13", a dramatization of the Apollo 13 mission, in which actor Tom Hanks, portraying Mission Commander Jim Lovell, uses that wording, which became one of the film's taglines.
Jack David Fischer (born January 23, 1974) is an American engineer, test pilot and a NASA astronaut.
 Fischer was selected in June 2009 as a member of the NASA Astronaut Group 20 and qualified as an astronaut in 2011.
 He made his first spaceflight in April 2017, as a flight engineer for Expedition 51/52 on the International Space Station.
Richard Francis "Dick" Gordon Jr. (born October 5, 1929), (Capt, USN, Ret.)
, is a former American naval officer and aviator, chemist, test pilot, and NASA astronaut.
 He is one of only 24 people to have flown to the Moon, as the Command Module Pilot for the Apollo 12 mission.
Robert Franklyn "Bob" Overmyer (July 14, 1936 – March 22, 1996), (Col, USMC), was an American test pilot, naval aviator, aeronautical engineer, physicist, United States Marine Corps officer, and USAF/NASA astronaut.
 He was born in Lorain, Ohio, but considered Westlake, Ohio his hometown.
 Overmyer was selected by the United States Air Force as an astronaut for its Manned Orbiting Laboratory in 1966.
 Upon cancellation of this program in 1969, he became a NASA astronaut and served support crew duties for the Skylab program and Apollo-Soyuz Test Project.
 In 1976, he was assigned to the Space Shuttle program, and flew as pilot on STS-5 in 1982, and as commander on STS-51-B in 1985.
 He was selected as a lead investigator into the Space Shuttle "Challenger" disaster, and retired from NASA in 1986.
 Ten years later, Overmyer died in Duluth, Minnesota while testing the Cirrus VK-30 composite homebuilt aircraft.
Stuart Allen "Stu" Roosa (August 16, 1933 – December 12, 1994), (Col, USAF), was an American aeronautical engineer, United States Air Force pilot, test pilot, and NASA astronaut, who was the Command Module Pilot for the Apollo 14 mission.
 The mission lasted from January 31 to February 9, 1971 and was the third mission to land astronauts (Alan Shepard and Edgar Mitchell) on the Moon.
 While Shepard and Mitchell spent two days on the lunar surface, Roosa conducted experiments from orbit in the Command Module "Kitty Hawk".
 He was one of only 24 people to travel to the Moon.
Theodore Cordy "Ted" Freeman (February 18, 1930 – October 31, 1964), was an American aeronautical engineer, U.S. Air Force officer, test pilot, and NASA astronaut.
 Selected in third group of NASA astronauts in 1963, he was killed a year later in the crash of a T-38 jet, marking the first fatality among the NASA Astronaut Corps.
 At the time of his death, he held the rank of captain.

Question: "Houston, we have a problem" was an erroneous quote between "Huston" and an American test pilot, NASA astronaut and one of how many people who have flown to the moon?
Answer: 24