The three days of testing have also been thrown open to regular teams to try out tyres under restricted circumstances after a spate of blowouts at last month's British Grand Prix at the circuit.
However, Britain's Paul Di Resta, at the wheel of a Force India, was the only race regular on track on the opening day.
Red Bull postponed to Thursday a run by Australian Daniel Ricciardo, the Toro Rosso racer who could replace compatriot Mark Webber at the world champions next season, after clarifying the conditions set by the governing FIA and tyre supplier Pirelli.
Webber is leaving Red Bull at the end of the year and had been due to test a new tyre to be introduced at next week's Hungarian Grand Prix, but he had his scheduled half day cancelled.
"It's an opportunity to have a look at Daniel and for him to do some of our tyre-testing work...it's a great opportunity for him," Red Bull principal Christian Horner told Sky Sports television in the Silverstone paddock.
Lotus also shelved plans to give 2007 world champion Kimi Raikkonen, the other main candidate to replace Webber, track time on Friday.
"Once details of what race drivers were allowed to do here became apparent, we would have only been able to conduct a very limited programme with Kimi," trackside operations director Alan Permane told the team website.
"If we were to run him, it would compromise the other development work we want to do with the car here."
Mercedes are absent as punishment for taking part in a 'secret' tyre test with Pirelli in Spain in May with their current car and drivers Lewis Hamilton and Nico Rosberg.
Lotus chose to give Frenchman Nicolas Prost, the 31-year-old son of five times world champion Alain, more time in the car. Prost is five years older than Red Bull's triple champion and current series leader Sebastian Vettel and can hardly be categorised as a young driver.
Nor can long-serving McLaren tester Gary Paffett, 32, or Williams development driver Susie Wolff, who is 30 and will be taking part in her first proper F1 test on Friday.
Young driver testing has been a money-spinner for some cash-strapped teams in the past, who have used the sole in-season testing opportunity to secure extra revenue rather than focusing strictly on talent.
However, most of those testing this week have shown their skills in the various junior series and some have genuine prospects of reaching the pinnacle of motorsport.
Portuguese Antonio Felix da Costa, testing for Red Bull, stands out as the one most likely in the near term. The Renault 3.5 series driver is tipped to replace Ricciardo at Toro Rosso if the Australian gets promoted to the sister team.