The Boeing's newest and most powerful rocket, the Delta 4, has finally blasted off from Cape Canaveral in Florida, US.

The vehicle lifted clear of the launch pad at 1739 local time (2239 GMT) on Wednesday on a mission to deliver a European telecommunications satellite into orbit.

We all know that the commercial marketplace today is a fixed pie

Wilbur Trafton, Boeing

The Delta 4 is part of a Boeing/US Air Force programme to develop more reliable and more economical rockets.

The biggest version of the rocket will challenge the European Ariane 5 and the Lockheed Martin Atlas 5 launchers for the top end of the heavy-lift market.

The Delta 4 should have flown on Saturday but was stood down when technical problems emerged. A further delay of a day was agreed on Tuesday when a liquid-oxygen valve started to play up.

Big push

The Delta 4 costs substantially less to build than its predecessors.

The rocket should be much cheaper to produce

The 60-metre-long (200 feet) vehicle is propelled by the first new major liquid-fuelled rocket engine made in the US since the development of the US space agency's shuttles in the 1970s.

The launcher comes in several variants based around its new first stage, called the Common Booster Core (CBC).

The rocket's second stage is an expanded version of the second stage used in the Delta 3 rocket.

Additional boosters can be used to supplement the first stage. The most powerful version of the rocket involves three CBC's strapped together to form the so-called Delta 4 heavy.

It will be able to place a payload of 13 tonnes into a trajectory towards geostationary orbit.

Competitive market

The Lockheed Martin Atlas 5 successfully debuted on 21 August. Europe's new 10-tonne Ariane 5 is set to launch from the Kourou spaceport in French Guiana on 28 November.

The new 10-tonne Ariane is being prepared for launch next week

Boeing officials were delighted to see their new vehicle finally get airborne.

"This is a new day and we, Boeing, have proved a lot to the industry here tonight," said Wilbur Trafton, president of Boeing's launch services. "Delta 4 is going to be around for a long time."

But there is currently a slump in the launcher market - there are too many rockets and not enough satellites to put into orbit.

"We all know that the commercial marketplace today is a fixed pie," Mr Trafton said. "Lockheed Martin and [Europe's] Arianespace and Boeing are all going after a fixed number of launches each year.

"We have positioned ourselves to be competitive, and we intend to take our share of the market," he added.