The Expendables Series by Richard Avery, Edmund Cooper

The Expendables were criminals, offered pardons in exchange for exploring alien worlds. But their mission takes them to Kratos, where the local lifeform is giant, slimy and hostile!

First they went to Kratos - and faced the Deathworms. Then they went on to Tantalus and tried to fathom the Rings - which could only have been fabricated with the help of highly sophisticated machinery. And then they discover an alien spaceship orbiting the planet in strict silence and incommunicability. When they finally boarded the vessel, it was obvious that it had been derelict for centuries - as a result of some dreadful battle... moreFirst they went to Kratos - and faced the Deathworms. Then they went on to Tantalus and tried to fathom the Rings - which could only have been fabricated with the help of highly sophisticated machinery. And then they discover an alien spaceship orbiting the planet in strict silence and incommunicability. When they finally boarded the vessel, it was obvious that it had been derelict for centuries - as a result of some dreadful battle. Meanwhile down below, the enigmatic Rings lay waiting to deal with intruders - as they did the deadly vampire tree. Once again, Commander James Conrad and his team of Expendables faced their mission to find planets suitable for colonization. The second of a new series of books, The Rings of Tantalus seems guaranteed to further launch Richard Avery as a very special writer of modern science fiction novels. And there are more to come less

The probe reported no evidence of human life on Zelos. It should have been an easy mission. The planet was supposed to be remarkably like Earth.The Expendables were trained to expect the unexpected, but even they were surprised to discover homo sapiens 24 light-years away from Terra. These people were Viking-like. Tall. Strong. Armed. And ready to fight with their uninvited guests.Zelosian weaponry was primitive and no match for the Expendables' laser power... moreThe probe reported no evidence of human life on Zelos. It should have been an easy mission. The planet was supposed to be remarkably like Earth.The Expendables were trained to expect the unexpected, but even they were surprised to discover homo sapiens 24 light-years away from Terra. These people were Viking-like. Tall. Strong. Armed. And ready to fight with their uninvited guests.Zelosian weaponry was primitive and no match for the Expendables' laser power. But the Expendables wanted to colonize Zelos, not wipe out the population. So when the crew of the Santa Maria was asked to join the War Games, they accepted. They would have to prove themselves-- or perish . . . less

Argus looked good. The prospects for a settlement were excellent. So the crew of the star-ship Santa Maria was expecting a nice, relaxing holiday after facing the perils of Kratos, Tantalus, and Zelos. But their commander, James Conrad, knew better. A sixth sense--and bitter experience--warned him that Argus would have its own special brand of surprises... moreArgus looked good. The prospects for a settlement were excellent. So the crew of the star-ship Santa Maria was expecting a nice, relaxing holiday after facing the perils of Kratos, Tantalus, and Zelos. But their commander, James Conrad, knew better. A sixth sense--and bitter experience--warned him that Argus would have its own special brand of surprises. After their first encounter with the lethal vegetation they tried to be prepared--but nothing in the Expendables' extensive training could have readied them for the final deadly wonder Argus had in store. less