China's 74-year-old Teng Hsiao-ping, who said last week he wished he could be 12 again, had his first chance for American fun and fantasy today behind the controls of a space ship on a simulated mission and in the back of a stagecoach at an old-fashioned Texas rodeo.

The Chinese vice premier, on the second day of his tour of the U.S. hinterland, also rode in a model lunar rover, looked at moon rocks and, according to an American official, engaged in secret "quasi-negotiations" with oil men about future exploration of China's potential petroleum riches.

Teng looked and said he was tired after his strenuous Washington activities and his stopover in Atlanta. Nevertheless he seemed to enjoy himself.

Admitting that he is "a novice" in the space field, Teng was full of questions about the mechanics and the meaning of some of the advanced technology he was shown at the Lyndon B. Johnson Space Center, home of America's manned space program.

The high point was a simulated flight in the cockpit of a space shuttle with the vehicle returning to earth at twice the speed of sound. The realistic simulator which is used to train astronauts took Teng high over the California desert within sight of the Pacific before bringing him down to a runway landing.

He sat in the copilot's seat, looking and listening intently. The "Teng is my copilot" mission was the talk of the accompanying Chinese and American officials and press corps. Some called it "Marco Polo in reverse," the orient discovering the high technology world of space flight in the west. A photographer said, "It's the funnest thing he's done since he arrived in America."

Sen. John Glenn (D-Ohio), the first American to orbit the Earth in his astronaut days, said Teng on the simulated mission "made two approaches and didn't crash... Any time you can walk away it is a good landing."

For his part, Teng praised Glenn as a man who belongs to the heavens after his feats in space and "is an immortal." Glenn responded that "my constituents in Ohio call me many things, but that is not one of them."

After lunch at the space center, Teng spent the afternoon at his hotel where hundreds of pro-Taiwan demonstrators paraded outside. Leaflets were passed out from local Chinese calling on Teng to renounce communism and restore human rights on the mainland.

No activities were on his published schedule for the afternoon, and various officials said he was napping, receiving a courier from Washington, D.C., or relaxing.

However, there were indications that unannounced meetings were taking place, and an American official said conversations with oil industry executives were among them. On arrival at nearby Ellington Air Force Base this morning, Teng noted that Houston is the center of the petroleum industry and said he had come to learn of its advances.

Several American oil firms have bid for exploration rights in China. One said Teng's discussions with oil men were not to conclude deals but to set the framework of competition and display Chinese interest.

Energy Secretary James R. Schlesinger, who accompanied Teng here, told reporters that "the Chinese are eager to have American participation in exploration and, at a later stage, production [of their oil resources]." Schlesinger said U.S. firms might participate both in offshore and onshore drilling for China.

According to the Department of Energy, Peking is seeking financial as well as technological help from foreign oil companies. While China is believed to have large onshore and offshore petroleum reserves -- perhaps 100 billion barrels -- their extent and geology are largely unknown.

At present China depends mostly on coal, of which it also has very large untapped reserves. Petroleum is consumed at the rate of less than a pint per person daily, compared to U.S. consumption of about 4 1/2 gallons per person daily, according to DOE.

China's future impact on the world energy market, either as a supplier, or if its needs outstrip production, as an importer, could be of major effect on international markets.

Teng capped his day in Texas with a barbecue and rodeo in Simonton, 40 miles west of Houston. Although the "old, wild wild west" as recreated by the show's promoters is new to the Chinese leader, roping horses and other aspects of horsemanship are not. The tribesmen in Inner Mongolia, Teng recalled on his way to Texas, are skilled with their versions of the lariat.

After a dinner of barbecued ribs and chili at the rodeo, Teng donned a 10-gallon hat and watched as the redstarred flag of the People's Republic of China and the Stars and Stripes were trooped by on large white horses.

As Texans cheered, the Chinese vice premier was presented with a 14-year-old Brahma bull. He and his wife, Cho Lin, waved their hats in the air to a fanfare by the Texas band.

The strange combination of Chinese communists and Texas cowboys drew enthusiastic cheers from the crowd. Instructions to the cowboys and cowgirls in the Wild West rodeo were given on the public address system in Chinese and English.