Exoscientist

Thanks for that. I was irritated by the approach SpaceX was taking towards the Starship in that SpaceX was ignoring basic principles in spaceflight. The main point was that for high delta-v missions such as lander missions to the Moon or Mars, these are done most efficiently by adding additional stages. But instead SpaceX wants to keep the SuperHeavy/Starship as two-stages and instead do multiple refuelings. Another irritation was that SpaceX was ignoring the basic principle that you want to minimize upper stage dry mass as much as you can. This is because every extra kilo added to the upper stage dry mass subtracts directly from your payload. However, in making the Starship reusable, a whopping 80 tons, and with that much being subtracted from LEO payload, was added to the Starship being made reusable, going from a possible 40 ton expendable dry mass to a 120 ton reusable dry mass. Why is this approach taken? Because SpaceX has this fixation that the Starship must be the be-all-end-all for ALL of spaceflight. Then to get the cost per kilo they want, they need the Starship to be reusable. Then any extra mass added to dry mass is acceptable, no matter how much it is. But a simple cost analysis shows this is a fallacious approach. A SpaceX exec estimated “10ish” refueling missions for the Artemis lander missions using the Starship HLS. But Elon estimated an aspirational $10 million launch cost for a reusable SH/SS. But this would be $100 million for 10 reusable launches. But a single expendable launch would only be $90 million by which because of the higher payload SH/SS could do single launch missions both to the Moon and Mars. No refueling missions required, and not even the SLS being required. Another interesting calculation is to see how much mass SH/SS could get to Mars as an expendable in a single launch. Bob Clark

Good point. Fraser Cain did an interview with advanced space propulsion researcher Andrews Higgins about possibilities for interstellar flight. About 14 minutes in, Higgins makes the point extrapolation of global energy usage suggests sometime in the 23rd century we might be at the energy level needed for interstellar flight. So Star Trek got it right he notes. But I actually don’t think it will be that long. I think it will be on the order of decades, at least for sending small probes, because of the fact both nuclear fusion and space solar power are rapidly approaching. Robert Clark

Elon Musk suggested on Twitter that a much larger Starship might be able to travel to other star systems. His phrasing there is not the best since a chemical propulsion system, such as the Starship is, couldn't make such a flight. But many different proposals have been offered over the years to accomplish it. Surprisingly, one method that of using a fusion drive may be possible near term. The reason why I say it may be possible near term, within decades, is because of how rapidly the various different approaches to fusion power are progressing. Practical fusion power might be reached within a decade. For the fusion drive, it would then have to be made lightweight enough for a space propulsion system. That's not a guarantee but I think it should be doable within decades of the fusion power being reached. See one proposal discussed here: Robert Clark

Probably right. I started a new thread. Bob Clark

The many different approaches to nuclear fusion that are rapidly advancing suggest we will soon have fusion power, likely within 10 years. If so, then this fusion startup proposes a fusion powered rocket that could reach Mars within days and the nearest star system within 11 years: Bob Clark

Is it confirmed the hot gas RCS worked on the booster but not on the Starship? If so, then the propellant transfer test may have caused a fuel leak preventing the RCS from operating. Bob Clark

Thanks for that. Considering just how low cost the expendable SH/SS is, the same as the Falcon Heavy but at 3 to 4 times the payload, an expendable SH/SS has advantages for being able to conduct single launch missions to the Moon or Mars, assuming you have a separate lander(NOT landing the entire Starship on the surface.) Bob Clark

That is what I what I was trying to say. Phil Bono’s proposal predates Chrysler SERV and Phoenix SSTO. Bob Clark

Thanks for that. An expendable SH/SS could get in the range of 200 to 250 tons to LEO. That would be well more than enough to do its own single launch mission to the Moon or Mars, no SLS required. Keep in mind such an expendable launch is only in the $90 million cost range. While not at the $10 million aspirational rate Elon wants for full reusability, considering the amount of payload it could loft, it still would be a major improvement over what we have now, and literally orders of magnitude cheaper than the SLS. By the way, suppose as a SpaceX exec once suggested the Starship HLS would need “10ish” orbital refuelings. At the $10 million per launch rate for a fully reusable SH/SS that’s still $100 million. Then the single launch expendable approach would actually be in the same cost range as the fully reusable approach, anyway. See the calculations here: SpaceX should explore a weight-optimized, expendable Starship upper stage. https://exoscientist.blogspot.com/2024/03/spacex-should-explore-weight-optimized.html Bob Clark

That would be a lot of failures before getting to operational status. I hope it doesn’t take that many. Bob Clark

Update from SpaceX. The booster experienced a RUD after the landing relight before contacting the water: "Super Heavy successfully lit several engines for its first ever landing burn before the vehicle experienced a RUD (that’s SpaceX-speak for “rapid unscheduled disassembly”). The booster’s flight concluded at approximately 462 meters in altitude and just under seven minutes into the mission.“ https://www.spacex.com/launches/mission/?missionId=starship-flight-3 So SpaceX still has not demonstrated the Raptor can relight reliably in flight. In fact, all the Starship landing tests and actual flight tests have shown it is not reliable after relight in flight. Bob Clark

Actually, that relight lasted only about 2 seconds. We don’t know if the relight was planned to last that long or SpaceX ended it early or it ended itself because it failed. If SpaceX wants to prove the Raptor can relight reliably they need to redo another Starship landing test and ensure you get relights with no engines leaking fuel and catching fire for the full length of an actual burn. As I said SN15 still had a fuel leak and engine fire on relight. Bob Clark

You can’t ignore a major issue for Raptor engine reusability. If the Raptor can not be made to relight reliably then reusability absolutely can not work. After SN15 test where it managed to land without exploding, SpaceX called the landing tests successful even though there was still a fuel leak and fire on relight, and conducted no more landing tests. Based on the Starship landing tests, a Raptor always leaked fuel and caught fire after a relight. Based on actual SuperHeavy/Starship flights a Raptor always fails at some point after relight, whether or not a fire and RUD occurred. In fact, SpaceX still has not proven the Raptor can reliably relight while in flight without failing. Bob Clark

It should be noted the Starship during tests of the landing procedure, that at least one Raptor always leaked fuel and caught fire. Note even in the last two shown here, SN10 and SN15, there were engine fires on landing. For SN10 the engine fire led to the vehicle exploding a few minutes after landing. For SN15 the fire was extinguished before it caused an explosion. SN15 was called a “successful” landing test because it did not explode. But a Raptor still did catch fire also during this test requiring a relight. And SN11 experienced a catastrophic explosion after a fuel leak and engine fire after engine relight: . Bob Clark

Yes, but the losses during reentry were quite substantial. By the way it might be possible to get a Starship that doesn’t even need thermal tiles. The idea is you could have wing loading, vehicle weight per wing area, so small that reentry speed is reduced sufficiently that the metal skin can survive the reentry heating by itself. See discussion here: Reentry of orbital stages without thermal protection? UPDATE: 7/1/2019 https://exoscientist.blogspot.com/2019/06/reentry-of-orbital-stages-without.html BUT for this to happen you would need Starship to have the quite low dry mass speculated upon by Elon of only 40 tons: Bob Clark

Actually, we do know definitely that the engines did not all relight during the landing burn for the booster. That proves something went wrong at this relight, and the damage could even have occurred during the first relight during boostback except that burn was not long enough to cause loss of vehicle. If something goes wrong with the engines during flight, and it is a known problem to have occurred before during testing the first thing to suspect is that same issue is occurring again. Bob Clark

Congratulations to SpaceX on successful ascent firings of both stages. However, Angry Astronaut noted, it is likely the problem of the relight of the engines of the booster for landing was due to the hot staging method. Another possibility is the Raptors has had continuing problems on relight during the Starship landing tests where one or more Raptors leaked fuel and caught fire. Even the landing test called successful, one of the Raptors still leaked fuel and caught fire. I just saw that SpaceX has decided not to try the engine relight test during the Starship return, which does support the idea there are still problems on relight of the Raptors. Bob Clark

Yes. The plug nozzle, variously called the aerospike and aeroplug, was known about since the early days of the space program. Bono’s innovative idea was to use to it deal with the heating during reentry. The plug nozzle then to Bono had two benefits. It would improve engine performance for a SSTO, or a near-SSTO that used drop tanks, whose engines had to fire efficiently from sea level all the way to orbit and would solve the problem of the reentry heating for that stage returning from orbit. It was the reentry thermal control purpose for the plug nozzle for which Bono was granted the patent. If you look at the interviews of Andy Lapsa of Stoke Space such as by Everyday Astronaut and NasaSpaceflight it is this purpose for which Stoke Space is praised for their “innovativeness”. My opinion, Phil Bono should have been given credit for this innovation. Bob Clark

China will launch giant, reusable rockets next year to prep for human missions to the moon. News By Jennifer Nalewicki( livescience.com ) published 2 days ago China's new jumbo-size, reusable rockets are part of the country's plans to send humans to the moon by 2030. https://www.space.com/china-reusable-rockets-human-moon-missions This rocket the Long March 10 can get 70 tons to LEO, or 27 tons to TLI. The article only mentions this rocket doing a circumlunar flight but it might actually be able to launch a manned lander mission Robert Zubrin with his Moon Direct plan noted a manned lunar mission could be launched by the Falcon Heavy: Op-ed | Moon Direct: How to build a moonbase in four years Robert ZubrinMarch 30, 2018 https://spacenews.com/op-ed-moon-direct-how-to-build-a-moonbase-in-four-years/ Key for his plan is using a “lunar exclusion vehicle” (LEV) of ca. 12 ton gross mass that is hydrolox powered as a lunar ascent vehicle. This would require near zero-boiloff tech, but Zubrin thinks this is doable with current tech. Zubrin would also use a larger hydrolox stage for the lander descent stage at ca. 40 ton size, a bit smaller than Centaur V, that could deliver either the 12 ton manned LEV that could return to Earth orbit, or 12 tons of cargo one-way to the lunar surface. Quite notable about his plan is the manned flights it would require a single Falcon Heavy stage as the launcher to get the hydrolox in-space stages to LEO. The FH has a payload capacity of 63 tons to LEO. So an only 63 ton launcher could get the required in-space stages to LEO, which could then do a manned round trip flight to the lunar surface. This small size for the launcher is coming from the fact the in-space stages are so much lighter being powered by hydrolox. The Falcon Heavy is not man-rated so you would need an extra man-rated launcher like the Falcon 9 to get the astronauts to LEO. But the Long March 10 would be man-rated so could carry the astronauts to orbit. So it could do a manned landing mission in a single launch if hydrolox lander stages like in the Zubrin plan were included. Bob Clark

I noticed those Australian patents didn’t mention Bono’s name. I looked at Stoke’s U.S. patents. They also didn’t mention Bono’s name. In academic circles, you write a thesis or research work. You present it as your own work, but it was copied from another author or researcher. In academic circles, that is commonly ascribed a word beginning with the letter “p”. But suppose that earlier author is long dead and his copyrights expired. Should it still be ascribed the “p” word? Bob Clark

By that argument SpaceX should never have developed reusable boosters. Some such as ULA’s Tory Bruno are still saying its not worth it. Bob Clark

Actually it is worth it. Rather than the expensive and uncertain development of a full-flow staged combustion engine, they could accomplish the same thing far more cheaply by using the same multiple thruster around a central plug technique they are using for the upper stage, except with dense propellants. BUT this time they would actually use the altitude compensating effects of the plug nozzle. SpaceX has been developing the FFSC Raptor since 2016, and it is still not reliable enough to be considered an operational engine. It is said the SuperHeavy/Starship development cost has been in the range of $5 to $10 billion. Note then typically for a new launcher development using a new engine, the engine development costs make over half the entire development cost of the rocket. So likely SpaceX has spent billions overs those years since 2016 developing the Raptor. Bob Clark

My point is he did use the altitude compensating effects of the plug nozzle to improve performance. The increase in performance also applies to two-stage vehicles because it increases the performance of the first stage. See Bono’s ideas for SSTO discussed here: One Giant Leap: Philip Bono's ROMBUS. Updated: May 17, 2023 https://www.spaceflighthistories.com/post/rombus In any case, it is considered bad form in academic circles to take credit for something thought up by someone else. Bono is now long since dead, and his patents have expired. Undoubtedly though, Stoke Space in seeking funding believed it more attractive to their prospective funders to pass off Bono’s ideas as their own to get higher estimation of themselves in the eyes of the potential investors. Bob Clark

I’m a little annoyed with Stoke Space they didn’t credit Phil Bono who came up with the idea of using a plug nozzle for thermal shielding during reentry: https://twitter.com/rgregoryclark/status/1677672260159561729 By not crediting Bono they are missing a key aspect of his proposal: Bono wanted to actually use the altitude compensating effect of the aerospike/aeroplug. Stoke Space is ignoring that aspect of his proposal. But by ignoring that they are missing a key advantage of this type of nozzle: the aerospike/aeroplug is even more effective for first stages. Their plan is to use standard, fixed bell nozzles on the first stage with full-flow staged combustion engines: https://www.stokespace.com/rocket/ But actually altitude compensating nozzles such as the aerospike, among many other different kinds and types, can get even better performance than staged combustion engines and are far cheaper. Remember SpaceX with billions of dollars at its disposal still hasn’t gotten the Raptor to operate reliably. Since Stoke is already using a multi thruster plug nozzle for its upper stage, Stoke could be making concurrently a multi thruster plug nozzle for the first stage, except dense propellant rather than the hydrolox used on the upper stage. In fact since dense propellants are easier to work with than hydrolox, the first stage could even have been ready earlier than the upper stage. Robert Clark

The first listed call for proposals called THRUST! seeks proposals for staged combustion engines. But in point of fact altitude compensation can accomplish the same thing at far lower cost: Altitude compensation is more efficient than staged-combustion engines. https://exoscientist.blogspot.com/2024/02/altitude-compensation-is-more-efficient.html Bob Clark