SpaceX is continuing to move towards a first test flight of its Starship / Super Heavy launcher combination with the return of Booster 4 to the orbital launch facilities – although there is still some way still to go before an actual launch attempt will be made.
Following the test stacking of Booster 4 and Starship 20 on the launch table back in August (see Space Sunday: the Ups and Downs of Space Vehicle Development), Booster 4 was rolled back to the production facilities at the company’s Starbase centre at Boca Chica, Texas, to undergo a number of revisions.
Chief among these has been modification to the vent valve system, nominally used to allow excesses gaseous oxygen and methane to be vented from the rocket’s tanks as it naturally “boils off” due to temperature differentials the vehicle experiences when fuelled ahead of a launch. In particular, the vents for the booster’s lower tank now have covers that direct any gas downwards along the rocket’s body, and the vents for the upper tank focre the gas outwards and away from the rocket.
This suggests that SpaceX plan to use the release of gas from the tanks as a means to help control the orientation of the rocket during its descent back through the atmosphere in a manner similar to a more traditional reaction control system (RCS). If this proves to be successful, it means SpaceX have further reduced Super Heavy’s mass by avoiding the need for separate RCS systems and their tankage.
Another issue with rockets is that as the fuel tanks empty they lose internal pressure, and this can interrupt the steady flow of propellants to the engines. To prevent this, most launch systems utilise a reserve of helium that can be fed into the tanks as the propellants are burnt, maintaining the necessary tank pressure. To remove the mass created by a helium system, SpaceX have opted to use the rarer option of autogenous pressurisation. This draws a small flow of heated propellants before they reach the engines, and feeds this flow – in gaseous form – back up the outside of the rocket via dedicated pipes to be returned to the fuel tanks to re-pressure them.
The new vent systems and the piping of the autogenous pressurisation feeds where clearly visible as Booster 4 was rolled back to the orbital launch facilities on Tuesday, September 7th, and hoisted back onto the launch table, with the speculation iit may remain there until the actual launch attempt.
When this will be is unclear; the operation to hoist the booster into position showed the launch table itself is still being completed, being wrapped in scaffolding. It’s also not clear how much of the necessary propellant and electrical feeds have been installed in the launch support tower – although the Quick Disconnect (QD) arm that actually feeds propellants into the Starship vehicle and provide it and the booster with electrical power has been installed (with further additions to come). Similarly, the actual tank farm that will supply consumables – water, propellants, etc., – to the pad to enable launches.
Even so, SpaceX CEO Elon Musk has suggested an initial static fire test with Booster 4 could come within the next week. Even if the majority of the required plumbing, etc., is in place, this seems possibly ambitious, given that such a test will likely only come after at least one each of cryogenic propellant loading / pressurisation tests which will take pre-and post test checks.
How many static fire tests might be run is unclear; its unlikely that SpaceX will want to fire all 29 engines in the first test but will likely build up to it – perhaps starting with the three motors at the centre of vehicle, followed by a firing of all nine of the middle engines before progressing to firing all 29 engines. And it should be remembered any of these tests, from pressurisation through the engine firings, could result in the rocket sustaining damage or even being completely destroyed.
After the August stack test, Starship 20 was moved from the the orbital launch pad to sub-orbital launch pad B, where it has been undergoing an extensive examination of its thermal protection system (TPS) designed to protect it during entry into the atmosphere. The tiles on this system appear to have suffered more than the anticipated amount of stress / damage due to it being lifted up onto the booster by its snout in order to be stacked on the booster, requiring a lot of them to be replaced and others refitted / re-aligned. This work is now drawing to a close, but does point to a need for the tile system to be more robust if rapid turnarounds of Starships is to be achieved in the future.
Most recently, the vehicle has been receiving the six Raptor motors that will power it. This has sparked speculation that once this work is complete, Starship 20 could be ready to start its cryogenic and fuel pressurisations tests ahead of static firing test – again, possibly the inner three first, then all six.
A final element key to any launch attempt (and the full booster static fire test) is the granting of permission and a licence by the Federal Aviation Administration, which appears to be rightly determined not to be rushed into giving the OK whilst it is still conducting an extensive review of the Starbase facilities and their overall suitability for Super Heavy / Starship launches in the event of an accident (particularly after the airborne explosion of Starship SN11in march 2021 resulted in debris falling to earth 8 km from the SpaceX facilities and close to a populated area).
Star Systems Naturally Create Interstellar Travellers
Ever since the interstellar objects ‘Oumuamua and 2I/Borisov swept through the solar system in 2017 and 2019/2020 respectively, there has been a lot of research into just how many of these pieces of debris from other star systems might be floating around in interstellar space and how they might originate.
The theory has been that they are objects found within Oort clouds around other stars (the “leftovers” of planetary formation) that for some reason or other get shunted out into interstellar space. While it is only an estimation, it is thought that each star around us gives rise to many thousands of these objects (the “guessimate” averaging said to be 9,000 per star), with around 5 of them passing through our solar system every year – the majority of which we simply don’t see (CNEOS 2014-01-08, currently zipping through the outer solar system at 216,000 km/h) is believed to be the third such object discovered, although this has yet to be confirmed).
However, a new study suggests this theory is incorrect. Researchers at the Centre for Astrophysics (CfA) at Harvard University, carried out computer modelling using what is called the mean mass solar nebula (MMSN) model, together with the various “guessimates” as to the number of per-star ‘Oumuamua / 2I/Borisov sized objects and the estimates of the average number of rogue planets stars produce (2-5) and their mass to try and work out how much material would be required to create them.
The results are surprising. The MMSN states that material equivalent around 1% of the mass of the Sun was needed to create all the planets, moons, asteroids, comets, etc., of the solar system – but it would require twice this amount to `match the estimated number of ‘Oumuamua / 2I/Borisov sized objects and 2 or 3 rogue planets. While the authors of the study acknowledge there work is in part speculative and open to challenge (and encourage more research on the matter), it does tend to squash the idea that ‘Oumuamua / 2I/Borisov objects are result of occasional Oort cloud happenstance. Rather, it would appear that the objects are likely formed at the same time as their parent star is being born – and are literally blown away while the star initiates its nuclear fusions.
If so, then it likely means that the creation of interstellar objects is likely a natural part of the formation of planetary systems, not an after-effect, and that much more mass present in a star’s accretion disk is actually blasted away from it at the time of ignition that had previously been believed, which could alter our perceptions of the evolution of solar-like systems.
Inspiration Four Ready for Flight
Inspiration4, the first non-professional crewed space flight, has been set for launch some time in a 24-hour window opening at 01:00 UTC on Thursday September 16th, 2021 (20:00 EDT, Wednesday, September 15th), with the precise time of launch to be set on Monday, September 13th.
Funded by by billionaire Jared Isaacman, the flight is part of a broader initiative to raise US $200 million for St. Jude Children’s Research Hospital, Tennessee. Isaacman has already donated US $100 million, and two of the seats on the flights went to the winner of an entrepreneurial competition to raise money for the hospital, and the “winner” of a donation sweepstake that raised a further US $13 million.
Joining Isaacman on the flight will be Sian Proctor, winner of the entrepreneurial competition, and a geosciences professor at South Mountain Community College in Arizona who will serve as the mission’s pilot; Hayley Arceneaux, a physician assistant at the hospital; and Chris Sembroski, who was given his seat by a close (and unnamed) friend who won the sweepstake, an Air Force veteran now working for Lockheed Martin.
Launching from Pad 39A at Kennedy Space Centre, Florida, the four will fly into space on a modified Crew Dragon vehicle: as they will be spending a total of 3 days in orbit with no docking at the ISS, the forward docking port of the vehicle has been fitted with a large copula that will allow the crew unparalleled views when the capsule’s forward hatch is opened on reaching orbit.
In keeping with the medical roots of the mission, and because they haven’t gone through the same rigorous and extensive medical testing and training professional astronauts go through, the Inspiration4 crewmembers will perform a variety of experiments and record health data in support future human spaceflights. They will also fly a small payload of goods and items that will be auctioned off in support of St. Judes following their return to Earth.
Assuming all goes as planned, I’ll have more on the mission in the next Space Sunday update.
Mini NASA Round-Up
NASA / ESA Confirm JWST Launch Date
NASA and the European Space Agency have set the launch of the James Webb Space Telescope from the European spaceport in Kourou, French Guiana. The launch is due to take place on Saturday, December 18th, 2021. This is slightly later than the planned early November launch date, having been pushed back due to delays in launching a commercial satellite payload, which has now slipped from late September to the end of October, but which contractually must take place ahead of the NASA / ESA telescope launch.
House Budget Reconciliation: Something and Nothing for NASA
The US House Science Committee has approved its portion of a multi-trillion-dollar infrastructure spending bill that carries good and bad news for NASA.
The good is that it includes US $4 billion that will allow NASA upgrade much of its ageing physical infrastructure and facilities and a further US $388 million for climate change research. The bad news is the bill makes no mention of the US $5.4 billion NASA requested to allow it to offer a second contract for the development of the Artemis Project’s Human Landing System (HLS) – the vehicle(s) that will get crews between lunar orbit and the surface of the Moon.
HLS has been in a state of contention since NASA issued a single development contract to SpaceX. This initially caused Blue Origin and Dynetics, the two other contenders for HLS work, to complain to the Government Accountability Office (GAO), halting all HLS work for several months. After the GAO supported NASA’s decision, Blue Origin filed a suit against NASA / the US Government, again halting work on the project in a move that could delay it for months, something NASA had hoped might be avoided in requesting the additional funding, as it would have allowed Dynetics and Blue Origin to once again compete for a contract.
“Percy” Snags Two Rock Samples and Boosts Case for Past Life
The Mars 2020 science rover Perseverance has collected two rock samples that may have been in contact with water for a long period of time boosting the case for ancient life on the Red Planet.
As I recently noted, “Percy” has been parked at a small ridge dubbed “Citadelle” in which the rocks appear to have a different composition to the surrounding area. One of these rocks, dubbed “Rochette”, was selected as a site for sample retrieval, and on September 6th and 8th, 2021, two successful cores were taken from the rock by the rover.
The majority of each 6-cm long sample will remain sealed in its tube, to eventually be deposited in a cache of such tubes intended to be retrieved by a future sample return mission. However, a little of each sample was analysed by the rover’s own internal laboratory. This revealed that “Rochette” is basaltic in nature, which may help in radiometric dating, which in turn could help establish the geological history of Jezero Crater – when it formed, how long any lake it may have contained lasted, and how the climate in the crater changed over time.
More interestingly, the samples indicate the rock once had an extensive interaction with groundwater. This both strengthens the case for the crater once having had a lake and suggests the water was present for an extended period – possibly long enough for life processes to use it and the minerals in the rocks to give itself a kick-start. It’s also possible that due to the presence of salt minerals in the samples, they might have tiny bubbles of ancient Martian water trapped within them – although this will need more sophisticated analysis on Earth in order to be confirmed.