Elon Musk: SpaceX successfully upgrades Raptor engines from 2 Starship

SpaceX CEO Elon Musk, in his usual fashion, posted on Twitter a number of details related to the Starship launch vehicle, its Raptor engines and some upgrades awaiting each of them.

Upgrade announcement

In December 2021, the entrepreneur spoke about the ambitious goals associated with the Starship’s upgrades. Its fuel tanks have been increased and three more Raptor propulsion systems have been installed, which should result in a 50% increase in maximum thrust and significantly optimise payload parameters. The innovations are present in the latest version of Raptor and were added to the launch vehicle design during its assembly.

According to Musk, SpaseX is increasing the scope of ground testing of an improved version of the rocket engine. It now operates at 320 bar pressure in the main chamber as standard. Almost two years ago, in mid-February 2019, when the company first began testing the first completed full-scale Raptor prototype it was able to achieve a main chamber pressure of 269 bar for a limited time. This is slightly better than the Russian RD-180/RD-270 engines. The former is being fitted to the ULA Atlas V.

How long did it take to upgrade

SpaceX needed 1.5 years to provide clear evidence that at least one prototype engine could operate at that much chamber pressure for 60 seconds or more. It managed to achieve a respectable 330 bar and a short-term output of 225 tonnes of thrust, well ahead of the Russian-made RD-701, which has never flown. The latter on tests showed from 290 to 300 bar.

Meanwhile, the RD-180 engine runs on oxygen and paraffin, i.e. not on gas, but on fuel. For this reason, it is not quite correct to compare the Raptor with it. In a new tweet, Musk took into account his Russian colleague’s remark, but still insisted that the second version of the engine proved to be more powerful and advanced.

There are flaws in the Raptor engine

It is true that so far Raptor has not quite functioned correctly in terms of meeting the challenges of orbital-class flight. However, it has gone far from the pilot version and since then it has survived seven flight tests, five of which took place in six months. Meanwhile, the developers did not even attempt to launch Raptor 1/1.5 into orbital class, as the company favoured an upgraded version of the Raptor 2 engine.

As Musk explained, staff at the McGregor (Texas) campus are now working with the new setup, which features improved wiring and technical elements.

However, the biggest change in the rocket engine is the increase in maximum rated thrust by almost a quarter relative to earlier versions of the Raptor. In absolute terms, it was as high as 230 tonnes. This provides some expansion of the nozzle “throat” to increase power density with little reduction in efficiency. Regardless, Raptor 2’s design is robust and stable with a main chamber pressure rating of 330 bar, up 10 percent from Raptor 1.5.

SpaceX had planned to send Starship on its first test flight into orbit in the first two months of 2022. But permission for this from the U.S. Federal Aviation Administration until the end of 2021 has not been received. The deadline for granting permission was postponed until 28 February.