SpaceX has completed the largest static fire test for this Starship / Super Heavy launch system, with the 70-metre tall Booster 7 – expected to be part of the first orbital launch attempt – completing a “full duration” 5-7-second test of 31 of its 33 Raptor 2 engines.
The test was made on Thursday, February 9th, amidst on-going work at the orbital launch facilities at the company’s Boca Chica, Texas Starbase site. It had been intended to be full 33-engine test, but one engine was “turned off” during a pause in the countdown at the T -40 second mark, presumably due to an issue being detected, and a second automatically shut down at, or immediately following, ignition.
Even so, the burn was enough for the SpaceX CEO to proclaim the 31 firing engines developed sufficient thrust that, if sustained throughout an 8-minute ascent, it would be enough for Super Heavy to push a fully laden Starship to an altitude where it could reach orbit under the thrust of its six engines.
Ignition came at 21:13:53 UTC, after a partial filling of the booster’s liquid methane and liquid oxygen tanks – Starship 24 had already been destacked from the booster earlier in the month, leaving just the booster on the launch table. Everything appeared to go well, with SpaceX afterwards reporting the engines reached a peak thrust of 7,900 tonnes, or almost twice that generated by the Space Launch System Block 1/1A launcher, and 3,000 tonnes more than the Block 2 SLS cargo launcher.
However, such comparisons need to be put into context: Super Heavy must lift 1200+ tonnes of Starship to low-earth orbit (LEO), carrying 100 tonnes of cargo. SLS is already capable of lifting 95 tonnes of payload to LEO if required, which will increase to 105 tonnes and then 130 tonnes. It is also capable of delivering 27 tonnes to cislunar space, which will increase up to 46 tonnes. The flipside is that Starship and its booster are fully reusable, lowering launch costs; SLS is not. Also, if the booster is not re-used, they Starship could in theory life up to 250 tonnes to LEO; conversely, SLS can reach cislunar space, whereas Starship cannot, not without a complex series of on-orbit refuelling operations.
The test came after extensive work had been carried out at the launch facility after the first two Super Heavy static fire tests (with 7 and 14 Raptor motors respectively) literally stripped the concrete from the base of the launch stand, peppering the launch mount and its surroundings with high velocity cement debris and necessitating extensive repairs to the site.
The problem was one of basic engineering (and frankly, something SpaceX should have considered): the launch table legs and apron underneath the rocket are coated in concrete. A key ingredient of concrete is water, some of which is retained in the concrete as pockets of moisture. Heat concrete to 600°C or more, that moisture flash vaporises into expanding gases, causing the concrete to violently explode.
As I’ve previously noted, this risk is usually negated by the inclusion of a water deluge system which delivers thousands of litres of water to a launch facility, serving a dual purpose: it both absorbs the enormous heat generated by multiple rocket motors by flashing into stream by the force of that exhaust, and it also absorbs the sound waves generated by the motors, further preventing that sound being deflected back up against the rocket and potentially damaging it at launch.
Following the 14-engine test, SpaceX replaced the concrete at the launch facilities with a type designed to withstand very high temperatures. At the time of writing, it is not clear how well this mix withstood the engine test, however the test came at a time when SpaceX is – belatedly – attempting to install a water deluge system to work alongside the existing (and minimal) sound suppression system already part of the launch table.
Many – including the SpaceX CEO – are proclaiming the way is now clear for an orbital launch attempt to be made in March. However, this actually depends on a number of factors – the most key of which is whether or not the FAA is satisfied that SpaceX has done / is doing enough to ensure its compliance with all 75 remedial actions specified in its Programmatic Environmental Assessment (PEA).
NASA Tests Upgraded RS-25 Motor
The SpaceX static fire test overshadowed NASA’s test of its updated RS-25 engine for the Space Launch System.
The initial four SLS launches utilise a total of 16 refurbished RS-25 motors originally used with the space shuttle system and referenced as the RS-25D. However, beyond Artemis 4, NASA will be switching to a version of the RS-25 which has been extensively updated. Called the RS-25E, it will deliver 30% more thrust; allowing SLS achieve the upper end of its payload capabilities noted above.
The test, which took place at NASA’s Stennis Space Centre in Mississippi, saw a test stand mounted RS-25E motor fire at 111% of its rated thrust for a total of 8.5 minutes – the amount of time the engines would be used in an actual launch.
The RS-25E will commence operations with the Artemis 5 mission in 2028. They will operate alongside the new Exploration Upper Stage (EUS) which will also help raise the SLS system’s performance. EUS itself will entire service with Artemis 4.
Image of the Week
The image below is a computer-generated top-down view of Jupiter and the orbits of its (currently) 92 moons. At the centre of the image is Jupiter and (purple) the orbits of its four most famous Galilean moons – Io, Europa, Ganymede and Callisto. Beyond them, predominantly shown in red, are the remaining 88 moons.
Until recently, Saturn held the record for the greatest number of moons (82), the majority of which (43) have been discovered by a team led by astronomer Scott Sheppard. However, Sheppard’s team have also been busy over the years seeking moons orbiting Jupiter – racking up and impressive 70, including the most recent batch of 12 which handed the moon record back to the largest planet in the solar system.
The newest moons were discovered over a period of observations by Sheppard and his team using a number of observatories around the world across 2021 and 2022. They range in size from 1 to 3.2 km across. Most have very large orbits, with nine having periods of more than 550 days. None have been named as yet, as all are awaiting further independent verification.
Continue reading “Space Sunday: rockets, moons, leaks and a ring”