Exoscientist

If this new high temperature material is able to solve the Starship thermal protection issues, I think SpaceX would accept this relatively mild criticism anyway. Bob Clark

New high temperature ceramic heat shield materials promoted to SpaceX: AN OPEN LETTER TO ELON MUSK. Dr. Ed Pope https://www.linkedin.com/feed/update/urn:li:activity:7306136414910300160 Published 3/14/2025 MATECH, Cal Nano aim to commercialize UHT composites. The partnership’s combined technological advances and manufacturing prowess will target the scale-up and industrialization of FAST SPS for high-temp and UHT composites serving aviation, defense. https://www.compositesworld.com/news/matech-cal-nano-aim-to-commercialize-uht-composites Bob Clark

There are several variations of this inflatable heat shield idea. The most researched one is a conical inflatable heat shield. It’s being investigated for example as a heat shield to make the Cygnus cargo capsule reusable: Here’s a research article on it: HEART FLIGHT TEST OVERVIEW 9th INTERNATIONAL PLANETARY PROBE WORKSHOP 16-22 JUNE 2012, TOULOUSE https://websites.isae-supaero.fr/IMG/pdf/137-heart-ippw-9_v04-tpsas.pdf As discussed there the parameter used to measure the capability of a particular shape to slow down descent is not wing loading, weight divided by wing area, but the ballistic coefficient, (mass)/(drag coefficient*drag area), β = m/CDA, given in metric units. This takes into account the fact different shapes are more effective in slowing down the spacecraft by including the coefficient of drag CD as well as being more general than just looking at wings for the decelerator. In this report, the mass used for their analysis is 5,000 kg and the diameter of their conical decelerator is 8.3 meters. There is thermal protection applied but I gather less of it is needed since the conical aeroshell is just made of silicone rubber. If it is just ballistic coefficient determining this then for a spacecraft or stage about 9 times heavier, say, 40,000+ kg, then the area needs to be 9 times more, that is, a conical shell about 25 meters in diameter. This is useful for just drag decelerators, but is incomplete for winged reentry because it does not include the effects of lift. For instance if wings with high lift/drag ratio at hypersonic speeds were used the descent rate would be decreased even further. The hypersonic aerodynamics of the Space Shuttle have been described as falling “like a brick.” Then wings with high L/D ratio could greatly improve on this. Bob Clark

Still, I’d like to see the calculation. In the Space Review article, the idea was first proposed by the legendary spaceflight engineer Maxime Faget. So I’d like to see some calculations supporting or disproving it. Bob Clark

One of the criticisms of the Space Shuttle was it was so heavy, as an upper stage, for the payload it could get to orbit: ca. 80 ton dry mass, for only a ca. 20 ton payload. That’s the reverse of what it should be. For instance, for the Falcon 9 the upper stage has a ca. 4 ton dry mass for a ca. 20 ton payload. Note that if Elon’s estimate of the expendable Starship’s dry mass as 40 tons was accurate, then at a payload of 200 to 250 tons, the payload to upper stage ratio would be in the expected range of about 4 or 5 to 1. The Space Shuttle heavy weight resulted in poor, i.e., high, wing loading. From Grok: Query: What was the Space Shuttle orbiter wing loading in pounds per square foot? Response: … Final Answer: The Space Shuttle orbiter's wing loading was approximately 91 psf at launch and 76 psf at landing, with slight variations depending on the specific mission and payload. These values reflect its design as a reusable spacecraft optimized for both atmospheric reentry and gliding to a runway landing. The Space Review article wanted a wing loading of 10 pounds per square foot(psf) to require no thermal protection: Wings in space. by James C. McLane III Monday, July 11, 2011 The Space Review Wing loading (the vehicle’s weight divided by its wing surface area) is a prime parameter affecting flight. The antique aluminum Douglas DC-3 airliner had a big wing with a low loading of about 25 psf (pounds per square foot of wing surface). At the other end of the spectrum, the Space Shuttle orbiter has a high wing loading of about 120 psf. This loading, combined with an inefficient delta-shaped wing, makes the orbiter glide like a brick. A little Cessna 152 private plane features a wing loading of about 11 psf and modern gliders operate down around 7 psf. A space plane with huge lifting surfaces and a very low wing loading might not require any external thermal insulation at all. Building a space plane with a wing loading of, say, 10 psf should not be an impossible proposition. Perhaps some day it will be done. http://www.thespacereview.com/article/1880/1 If the expendable Starship did have a dry mass of 40 tons, 88,000 pounds, and say added wings gave wing loading of 10 psf what does KSP say the heating would be during reentry? Bob Clark Edit: I suppose this would have to be carried out in the Real Solar System mod rather than KSP itself.

Thanks for that. I discussed before I think it was a mistake for SpaceX not to go with expendable version of the Superheavy/Starship first then proceed to reusability, once the expendable version was proven. This approach was spectacularly successful with the Falcon 9. Taking this approach with the SH/SS they would now already be launching 250 tons to orbit, 10 times greater than the payload of the F9. And with the success at catching the SH booster, we may assume the per kilo cost would be reduced further still by partial reusability. Quite likely we would have single launch manned missions both to the Moon and Mars with partial reusability of less than $100 million cost now at less than what we are currently spending just for manned missions to the ISS. The approach that SpaceX is taken to reuse of the upper stage is also poor. Elon once estimated the dry mass of the Starship upper stage could be as low as just 40 tons as an expendable. Now the various modifications to the Starship for reusability, the dry mass is estimated as 160+ tons, an increase by a factor of 4 or likely more. For an orbital rocket you should try to minimize the weight growth of an upper stage as much as possible since that subtracts directly from payload. In that regard SpaceX should examine the possibility of using wings for landing instead of powered, vertical landing. Wings using lift can reduce the speed of descent thus decreasing the heat load on return, thereby reducing the thermal protection needed. The thermal protection used so far by SpaceX has not been successful. Reducing the heat load could reduce the amount of thermal protection needed. In fact, it might be it could even be reduced to zero. A surprising article: Wings in space. by James C. McLane III The Space Review Monday, July 11, 2011 Wing loading (the vehicle’s weight divided by its wing surface area) is a prime parameter affecting flight. The antique aluminum Douglas DC-3 airliner had a big wing with a low loading of about 25 psf (pounds per square foot of wing surface). At the other end of the spectrum, the Space Shuttle orbiter has a high wing loading of about 120 psf. This loading, combined with an inefficient delta-shaped wing, makes the orbiter glide like a brick. A little Cessna 152 private plane features a wing loading of about 11 psf and modern gliders operate down around 7 psf. A space plane with huge lifting surfaces and a very low wing loading might not require any external thermal insulation at all. Building a space plane with a wing loading of, say, 10 psf should not be an impossible proposition. Perhaps some day it will be done. http://www.thespacereview.com/article/1880/1 At the current overweight Starship mass, wings might be too large and heavy to get to this low wing loading but it might work if SpaceX went back to the expendable dry mass of only 40,000 kg. At such a mass, with the cross-section of the stage being 9 meters by 50 meters, and using the cross-section area of the cylindrical stage as “wing area”, the psf would be 40,000*2.2(pounds)/9*50*3.282 (sq.ft.) = 18 psf. Still not at the 10 psf point. But it’s close so that added wing area needed would be small: Typically, wings amount to about 5% to 10% of the dry mass. For such small wings it would be closer to the smaller number so only 2,000 kg added weight, and the psf would still be about the same 10 psf number. That Space Review article though gives no references where this contention of a 10 psf needing no thermal protection was derived. Can your spreadsheet calculate speed at intermediate points during descent? You would need to be able to do this for a calculation for the heating induced by the speed at each altitude and air density during the descent. Bob Clark

Air Force picks remote Pacific atoll as site for cargo rocket trials. By SETH ROBSON STARS AND STRIPES • March 4, 2025 https://www.stripes.com/theaters/asia_pacific/2025-03-04/cargo-rocket-pacific-johnston-atoll-air-force-17026030.html Surprisingly, just standard FedEX cargo aircraft delivery for the longest distance transpacific routes costs over $100/kg. Then when SpaceX does manage to get the cost orbit to $100/kg the cost for Starship transport at less than 1 hour travel time will be less than aircraft cargo delivery rates for the longest routes that might take a full day. I argue SpaceX already has this capability for such low launch cost with the Starship. It only has to take the approach, proven so successful with the Falcon 9, of first doing expendable launch, then partial reusability. Full reusability is unnecessary, and the recent failures with Starship suggest is more difficult than SpaceX expected. With such a strong financial motive for such fast point-to-point cargo delivery there is no doubt it would be implemented. Then at high flight rates this would serve to improve launch reliability, thereby bringing about such fast point-to-point transport for passengers as well. People have criticized SpaceX developing Starship on the grounds there would be no consistent market for such large mass to orbit. But this would be a key market, point-to-point cargo and soon thereafter passenger transport: Implications of the coming era of commercial heavy launch: point-to-point transport for both cargo and passengers. https://exoscientist.blogspot.com/2025/03/implications-of-coming-era-of.html Bob Clark

If it is true its size and payload will be V2-like then ChatGPT was giving the right estimate of ca. 100 tons. Bob Clark

Quote, “These days Elon can do essentially whatever the hell he wants.” Bob Clark

Are they downgrading the performance of Starship V3? Starlink sats at 550 km orbit. By ChatGPT, 100 tons at 550 km orbit corresponds to ca. 105 to 110 tons at a 200 km reference orbit: Query: If a rocket can get 100 tons to 550 km high orbit, how much can it get to 200 km high orbit? Response: … Rough estimate: A simple approximation (ignoring atmospheric drag and other losses) could give you a 5-10% increase in payload capacity to the lower orbit. So if the rocket can place 100 tons into a 550 km orbit, it could likely place somewhere around 105 to 110 tons into a 200 km orbit, depending on specifics. But SpaceX said V3 should get 200 tons to LEO. Bob Clark

Thanks for that. Just basic spaceflight engineering principles suggest Starship is too heavy for the role of a lander. SpaceX hires very good engineers. They know this. Unfortunately the actual engineers get overruled by Elon: Bob Clark

Another article critical of the multi-refueling approach SpaceX is taking to get to the Moon and Mars, that discusses Zubrin’s view as well as that of former high ranking NASA official Daniel Dumbacher: SpaceX Needs A New Mini-Starship To Land Humans On The Moon And Mars. By Kevin Holden Platt, Contributor. Kevin Holden Platt writes on space defense… Mar 17, 2025 at 11:33pm EDT … “Our approach today has a very low probability to match the ‘before 2030’ milestone for landing humans on the Moon,” Daniel Dumbacher, who formerly served as Deputy Associate Administrator of NASA’s Human Exploration and Operations Mission Directorate, in charge of the Artemis lunar landings, testified at the hearing. While he didn’t mention the fiery breakup of SpaceX’s Starship during its January flight demo, Dumbacher, now a professor in aeronautical engineering at Purdue University, said that the ship’s need to be refueled with super-cooled liquid oxygen and methane in low Earth orbit via multiple dockings with still-to-be-developed tankers - a complicated operation that has never been tested - before each flight to the Moon involves an assemblage of complex technologies that might not be perfected within the next five years. “We might have to build a lander - we might have to scale down the current lander,” Dumbacher told the House, “so that we get to that 2030 landing.” To avert potentially spiraling problems with testing the colossal Starships during the countdown to this new Moon quest, he said, “I’d get myself a simplified lander - so that I can get to the Moon - that does not require multiple launches.” … https://www.forbes.com/sites/kevinholdenplatt/2025/03/17/spacex-needs-a-new-mini-starship-to-land-humans-on-the-moon-and-mars/ Bob Clark

I’ve mentioned before Zubrin and others have argued the point using Starship itself as the lander to the Moon or Mars is a bad approach. It is far too heavy for that role. Standard engineering practice is to add additional, smaller stages, to get to high delta-v destinations such as the Moon or Mars. Apollo for instance, even higher delta-v being round-trip, used 6 propulsive stages. An article discusses this argument of Zubrin of using a smaller mini-Starship as the lander as well as the critical Will Locket review article here: Mini-Starship or bust? Experts clash over SpaceX’s future. https://floridamedianow.com/2025/03/spacexs-future/ I discussed the estimate of a $90 million unit production cost of the Superheavy/Starship here: https://forum.kerbalspaceprogram.com/topic/159887-spacex-discussion-thread/?do=findComment&comment=4428912 Bob Clark

At least you were able to finally make it to make it to the front of the line. Next time we go, we’ll have to make it at the least crowded times of the day, even if it’s, say, 3am. Bob Clark

Angry Astronaut discusses a critical review of the Starship that claims it can’t be made to work: (There is an audio glitch in the video. Fast forward to the 7 minute point.) In the video, Angry disagrees with the authors conclusions, the article being here: Starship Was Doomed From The Beginning. The fatal flaw SpaceX can’t overcome. Will Lockett Published in Predict 8 min read https://medium.com/predict/starship-was-doomed-from-the-beginning-743bf809539c The authors primary argument is the desire to make the upper stage reusable is making it too heavy. Angry Astronaut critiques this argument by saying the Space Shuttle was 100% reusable. This is not correct for the entire Space Shuttle system since the external tank was expendable. But it is true that the upper stage, the orbiter itself, was reusable. Still, it has long been discussed in the field a criticism of the space shuttle system was how heavy that upper stage was compared to the payload. The dry mass of the shuttle orbiter was about 80 tons. But the payload was about 24 tons. The reusable upper stage was nearly 4 times heavier than the payload. This is backwards in accordance to how normal rockets work. Normally you want to make that dry mass for the upper stage as low as possible since every extra kilo added to an upper stage dry mass subtracts directly from the payload possible. Normally, the payload would be multiple times more than the dry mass of the upper stage. For instance for the F9 the payload is ca. 20 tons, but the upper stage dry mass is only ca. 4 tons. And for the Saturn V the payload to LEO was 100+ tons, while the dry mass of the upper stage, the 3rd stage, was only ca. 15 tons. Quite interestingly, in regards to the Starship the payload for V1 according to Elon is only in the range of 40 to 50 tons, despite the original plan of 150 tons capacity. And indeed the dry mass of the Starship V1 is in the range of 160+ tons, quite analogous to the ratio for the reusable Space Shuttle orbiter of the dry mass of the upper stage being ca. 4 times more than the payload. SpaceX recognized this is too low a payload for a rocket of the Superheavy/Starship size and wants to make the rocket larger to get to its desired payload capacity. Both attempts of flying the larger V2 upper stage resulted in the stage exploding in flight. The author of this critical review article argues its because of the need to lighten the dry mass of the vehicle to get the desired payload. I don’t know if that is the case, but it should give SpaceX pause that in the V1 version, the one we know so far that can get to orbit, the payload had the same small proportion of the dry mass of the upper stage as did the Space Shuttle of only one fourth. Bob Clark

I can guarantee you Elon Musk is not designing the electronics that go into the Starlink satellites. The problem is he is making engineering decisions on the Starship, overruling the actual engineers: In the development of the Falcon 9 they followed standard industry practice of doing full-up(all engines), full mission duration, full thrust engine testing to first make expendable flights to orbit. If they had followed that standard engineering practice with the Starship, it would already be making paying flights to orbit, and at 250 ton to orbit capacity could be making at least demonstration missions to the Moon and Mars. Bob Clark

If the SuperHeavy/Starship cost $2 billion like the SLS that would be a strong reason not to want to use it in an expendable or partially reusable fashion. But its estimated production cost is ca. $90 million, ca. $60 million for the Superheavy and $30 million for the Starship. That in itself is a revolutionary reduction in the cost to space. That literally means, at least in regards to the cost to SpaceX, that flights to the Moon and to Mars can be mounted for less than what is currently being charged by SpaceX to send crew to the ISS. But it’s even more stunning than that. Falcon 9 and and now the Superheavy have demonstrated they can do landings. Then say the SuperHeavy can do, say, 10 reuses, then the cost to SpaceX to launch drops down to ca. $6 million for the Superheavy. Then with the ca. $30 million for Starship that’s ca. $36 million for a launch to the Moon or to Mars. That is NOW. Not in 2028 or the 2030’s. NOW. Let me put it this this way, Instead of responding about when we can send missions to the Moon and Mars by saying perhaps in 2028 or the 2030’s, the answer instead would literally be: on the next test flight next month. Bob Clark

250 Tonnes to Orbit!?: SpaceX's New Expendable Starship Option. https://m.youtube.com/watch?v=UutHG8Y2UuQ Elon has spoken of a flaw in engineering design of “doubling down on a bad design”. He is committing that error with the Starship. Requiring that the Starship must be fully reusable before it is operational was a bad design choice from the start. The Falcon 9 was spectacularly successful by first aiming for an expendable rocket, then proceeding to reusability. However, Elon wants the Starship to be fully reusable first. This is becoming increasingly difficult. If you think about it, it is this requirement that is a major cause of the difficulties. The need for reusability of Starship drastically increased its dry mass. Elon once estimated its dry mass as low as 40 tons as expendable. Now requiring it to be reusable at least quadruples that dry mass to 160 tons or likely even more. That radical increase in dry mass requires to make the Starship larger to get their desired payload. But then heavier mass already means more difficult thermal protection. And in fact the one they had used for several test flights had to be abandoned. At this point they don’t even know what thermal protection they’ll use. They don’t even know if they’ll even be able to find one that works at sufficient light weight that at the same time allows rapid reuse. SpaceX had stunning success in developing the Falcon 9 yet they chose to ignore that success. If they had followed that model they would already be flying the Starship as expendable at a profit. We would already have an operational rocket capable of both Moon and Mars missions NOW. Bob Clark

6 out of 8 explosions of your rocket in flight is indicative of bad engineering. Making the same mistake again after your vehicle explodes causing it to explode twice in a row is indicative of bad engineering. For any other space company such poor engineering would result in severe questioning of the Chief Engineer. Unfortunately for SpaceX, the Chief Engineer is the owner of the company. Questioning him results in YOU being the one getting fired. Bob Clark

Repeated engineering failures stem from the top. What SpaceX needs to do first is hire a true Chief Engineer. Then follow standard industry practice of doing full-up(all engines), full mission duration, full thrust static tests. Bob Clark

The suggestion that a Moon landing can be mounted with a launcher at ca. 60 ton payload capacity is derived from a proposal from the early 1990's for a low cost follow-up to Apollo called Early Lunar Access(ELA): Moon denied: the 1993 Early Lunar Access proposal. by Dwayne A. Day Monday, January 9, 2023 https://www.thespacereview.com/article/4511/1 It would use a Gemini-sized capsule for a 2-person crew lunar mission at ca. 3 tons dry mass for the capsule. Studies had shown the Gemini capsule could be adapted to carry a crew of two for a lunar mission. Unlike, Apollo there would be only this one crew module that would go all the way to the surface of the Moon and back to Earth, in contrast to the Apollo architecture that had a second smaller, crew module for the lunar lander. Interestingly, the hydrolox lunar lander stage would have about the same gross mass as the fully fueled Blue Moon MK1 lander with a 3 ton dry mass crew capsule added, i.e., ca. 25 tons. The plan was to use only one other additional in-space stage, a Centaur-like stage to perform the translunar injection(TLI) burn. This stage and the lander stage would be launched separately and link up in low Earth orbit. A spaceflight rule-of-thumb is a hydrolox Centaur-like stage can get a payload mass of equal size to its prop load mass to TLI. So a hydrolox stage would be needed at 25 tons or more prop mass. Centaur itself did exist at ca. 20 tons but a slightly larger one would be needed. The ELA plan was proposed in 1993, perhaps they were thinking of an extended Centaur. In any case, a hydrolox stage of the needed size did come into play with the Delta IV Heavy's upper stage, first launched in 2004. Besides that problem, the plan was to have the 25 ton hydrolox lander launched on the Space Shuttle. The shuttle then would need its payload capability expanded slightly to 25 tons. Another issue is NASA for safety reasons did not want a hydrolox stage in the shuttle payload bay. For these reasons the plan did not progress beyond just the proposal stage. But now we do have a hydrolox upper stage in the DIVH upper stage of the needed size to do the TLI burn. And we do have a launcher at 60+ ton capacity in the Falcon Heavy. The Falcon Heavy would need to be man-rated or Falcon 9 would need to be launched separately to get the crew to orbit. The New Glenn at 45 ton payload capability as partially reusable likely could also get ca. 60 tons to orbit expendable.

Finally, people are starting to ask the tough questions about the SpaceX development of Starship: Twin Test Flight Explosions Show SpaceX Is No Longer Defying Gravity. Consecutive losses of the Starship rocket suggest that the company’s engineers are not as infallible as its fans may think. … But these two Starship explosions were a step backward in SpaceX’s development process, as the flights could not even repeat the successes of earlier test flights, and they perhaps show that the company’s engineers are not as infallible as fans of the company sometimes like to think. “There’s this persona that has built up around SpaceX, but you’re starting to see that they’re human, too,” said Daniel Dumbacher, a former NASA official who is now a professor of engineering practice at Purdue University and chief innovation and strategy officer for Special Aerospace Services, an engineering and manufacturing company whose customers include NASA, the United States Space Force and some of SpaceX’s competitors. https://www.nytimes.com/2025/03/08/science/starship-spacex-explosion-elon-musk.html (Behind paywall.) Repeated engineering failures stem from the top. SpaceX needs a true Chief Engineer making the engineering decisions. Bob Clark

SpaceX was spectacularly successful with the Falcon 9 by first aiming for an expendable launcher, then proceeding to reusability. If SpaceX took this approach with the Starship, they would already be flying a 250 ton capacity launcher that could make flights to the Moon and to Mars in a single launch now. Instead, they won’t let their launcher be operational until full reusability is achieved, and we don’t know when that would be. At this point SpaceX doesn’t even know what heat shield they will use for the Starship, having abandoned the one they had used on several flights. Blue Origin is a taking the approach of getting payload to orbit first, like what was done with the Falcon 9. Landing is a secondary, even minor goal initially. They plan on proceeding to a large lunar lander this year. Running the numbers this lander could serve to land a crew module at 3 tons mass on the Moon and could be launched on an expendable New Glenn or Falcon Heavy at a 60 tons to LEO capacity in a single launch. No multi-billion SLS, no refueling flights required. Bob Clark

https://youtube.com/clip/UgkxxzYSZbpeDTcua39lvmtSoTIhxsVG9IiS Actually, I was referring to the 4th flight. A Raptor exploded during the landing burn. The booster then exploded just before ocean touchdown. In this flight it has been taken as the ocean touchdown causing the explosion. However, it actually occurred just before touchdown. Then strictly speaking you can consider this also as an explosion in flight. Bob Clark

SpaceX is in real danger of being lapped by Blue Origin. Blue demonstated the importance of having a top-notch Chief Engiineer in David Limp in reaching orbit on the first flight and rapidly progressing towards landing a large lander on the Moon on an upcoming flight. SpaceX demonstrated the importance of having a top-notch Chief Engineer in not having one. Bob Clark