Exoscientist

Thanks for that. I used to listen to those FISO presentations all the time. Sort of forgot about them. Looks like a good detailed presentation of their proposal. Holder is a former Air Force officer so makes sense he would be able to get the Air Force interested. Bob Clark

Could that for example take the specs for the Delta IV and Atlas V rockets and accurately output the payloads to LEO, GTO, etc.? The Silverbirdastronautix.com payload estimator can do that within about 10% accuracy I’ve found. But it does have wide cited error bars, i.e., you can only be sure of the answers within that rather large error range. Another thing I want to estimate is fast flights to the Moon or Mars. For instance Elon once said the expendable Starship might have a dry mass of only 40 tons. That combined with a 380s Isp would allow 1 month flights to Mars with just chemical propulsion: That is just an estimate though based on the idea the departure speed is so fast the trajectory would be almost straight-line. It would be nice to have an actual trajectory sim that would calculate this more definitively. With departure speeds that high it should mean near straight-line trajectories from LEO to the Moon also, with greatly reduced travel times. We might want this with commercial flights to the Moon by, for example, SpaceX coming into play in a near term time frame. With just a 3.1 km/s escape velocity, we can reach the Moon within 3 days. How fast from LEO to lunar orbit with, say, 12 km/s delta-v available, taking into account you also have to slow down? Could the travel time be reduced to hours? Bob Clark

I remember asking on this forum once why Kerbal used Kerbin and Mun, rather the real Earth and Moon and other real planets in the Solar System. I remember being not really being satisfied with the answer. I think with the interest in universities and schools worldwide in spaceflight, there would be a great deal of interest in having a program where they could design real rockets for making real missions anywhere in the Solar System. Bob Clark

This part must be what they were just “hoping” for. If true, it would mean a mass ratio of the rocket itself aside from the payload of 60 to 1. That’s not reasonable. There is also the fact the 20 kg tank plus 10 kg engine section would already be 30 kg with no mass left over for any other systems. Plus, running the numbers, with a dry mass that low, you would get payload to LEO in the range of 50 to 60 kg, not the ~10 kg they are claiming. The Mockingbird rocket had a more realistic 20 to 1 to mass ratio, with a 75 kg dry mass. Bob Clark

On their LinkedIn page, Sidereus said their engines are pump fed: https://www.linkedin.com/posts/luca-principi-2801981a9_cold-flow-tests-on-the-eos-mr-5-engine-activity-7214905823716646912-0eqv The company co-founder gave an interview on Next Big Future about their rocket: Bob Clark

Too bad KSP2 didn’t take off. Couldn’t more exposure and revenue be generated by marketing it as an actual commercial sim for spaceflight to orbit and interplanetary trajectories? There is nothing in the open market that does this now in an accurate way. I like using Silverbidrastronautics.com payload estimator but it’s at best only within 10% accurate and it also has wide potential error bars. It also has poor accuracy for large SRB’s like the space shuttle, SLS, Ariane 5/6. Governmental software like POST and OASIS are ITAR restricted and are highly non-user friendly. Believe me, I tried. KSP being European would not be subjected to ITAR. Bob Clark

But wasn’t that the case also with KSP1? Bob Clark

This forum worked perfectly fine with KSP1, why does the failure of KSP2 threaten it? Bob Clark

According to SpaceX after soft water landing the Superheavy was not expected to explode. This was found by a reader on Reddit in SpaceX’s environmental impact statement: It would be contrary to what SpaceX notes in their 2023 PEA revaluation documents though. After the landing burn ends, the flight plan is for Super Heavy to impact the water vertically and intact. Then, within several seconds, Super Heavy would tip over and impact the water horizontally. The landing would impart forces onto the liquid oxygen (LOX) tank and methane tank; however, the tanks’ structural capabilities allow it to withstand these forces. Therefore, the tanks would remain intact, and there would be no resultant interaction between the LOX and methane. Super Heavy is expected to remain intact. That was a very large fire that erupted up the side of the rocket after the landing burn. Remember that large fire visible on the outside is stemming from fuel burning on the inside of the engine compartment. Bob Clark

The fact the explosion was large enough to create a mushroom cloud of that size is disturbing. That is not something SpaceX would want to reveal for a landing attempt of the Superheavy on land. Bob Clark

Since SN10 also exploded after landing when it had caught on fire prior to the landing, its likely the same thing happened here: Bob Clark

The validity of this clip has not been confirmed: http://x.com/CSI_Starbase/status/1809452742290583619 Bob Clark

Good point. Assuming it is similar to the Mockingbird design that @AckSed linked, https://up-ship.com/blog/?p=11056, then it would have a dry mass in the range of 75 kg and a gross mass in the range of 1,500 kg. DARPA had wanted an air-launched system for small payloads at $1 million launch cost for a 45 kg payload with their ALASA program: The ALASA rocket, measuring 7.3 meters long, would be attached to the underbelly of a Boeing-built F-15E fighter aircraft. DARPA says taking off from a standard airport runway would allow the Defense Department to launch from almost anywhere. Credit: Boeing artist's concept. https://spacenews.com/40023boeing-targets-66-percent-launch-cost-reduction-with-alasa/ See discussion here: Dave Masten's DARPA Spaceplane, page 2: an Air Launched System. http://exoscientist.blogspot.com/2014/08/dave-mastens-darpa-spaceplane-page-2.html Boeing initially was investigating the possibility but pulled out of the program. I believe they pulled out not because they couldn’t get it to work, but because they couldn’t make enough money on it. (See my sig file.) But at the specifications of Mockingbird, and perhaps Sidereus, it could easily make the DARPA requirements. This research report investigated the advantages of air-launch: A.4.2.1 Launch Method Analysis (Air Launch). For a launch from a carrier aircraft, the aircraft speed will directly reduce the Δv required to attain LEO. However, the majority of the Δv benefit from an air launch results from the angle of attack of the vehicle during the release of the rocket. An ideal angle is somewhere of the order of 25° to 30°. A study by Klijn et al. concluded that at an altitude of 15250m, a rocket launch with the carrier vehicle having a zero launch velocity at an angle of attack of 0° to the horizontal experienced a Δv benefit of approximately 600 m/s while a launch at a velocity of 340m/s at the same altitude and angle of attack resulted in a Δv benefit of approximately 900m/s. The zero launch velocity situations can be used to represent the launch from a balloon as it has no horizontal velocity. Furthermore, by increasing the angle of attack of the carrier vehicle to 30° and launching at 340m/s, a Δv gain of approximately 1100m/s was obtained. Increasing the launch velocity to 681m/s and 1021m/s produced a Δv gain of 1600m/s and 2000m/s respectively. From this comparison, it can be seen that in terms of the Δv gain, an airlaunch is superior to a ground launch. As the size of the vehicle decreases, this superiority will have a larger effect due to the increased effective drag on the vehicle. https://web.archive.org/web/20120229141110/https://engineering.purdue.edu/AAE/Academics/Courses/aae450/2008/spring/report_archive/reportuploads/appendix/propulsion/A.4.2.1 Launch Method Analysis (Air Launch).doc The 681 m/s launch velocity mentioned is about Mach 2, and the 1021 m/s velocity about Mach 3. The F-15 jet fighter planned for the ALASA air-launch could get about Mach 2.5, So estimate the delta-v savings as intermediate between the 1600 m/s and 2000 m/s mentioned so about 1,800 m/s. Taking the required delta-v to orbit as about 9,200 m/s, the small orbital rocket would only have provide about 7,400 m/s delta-v. For launch at high altitude take the Isp as close to the vacuum Isp of, say, the Merlin Vacuum of 348s. By the way, arguments that air-launch wouldn’t offer much delta-v benefit looked only at the aircraft speed but another key benefit is that launching at high altitude allows near vacuum Isp for the orbital stage, rather than sea level Isp. Then the Mockingbird/Sidereus rocket could get about 100 kg to orbit: 348*9.81Ln(1 + 1,425/(75 + 100)) = 7,550 m/s. Note the 10 times higher payload capability by using air-launch. Since DARPA wanted 45 kg at $1 million per launch, they might agree to pay $2 million for this much payload. The operational cost for the F-15 would be comparatively low cost compared to that: USAF: The F-15EX Costs Less than the F-35 | TURDEF The planes cost $80 million each, which is cheaper than the F-35. The USAF will receive another six units this year from Lot 1 production. The F-15EX is designed to last up to 20,000 flight hours at the cost of $29,000/hour. According to the report, this cost is a third of the operating cost of the F-35. Jan 20, 2023 https://turdef.com/article/usaf-the-f-15ex-has-a-higher-advantage-and-costs-less-than-the-f-35 Since Sidereus was planning to offer their rocket at only $100,000 this would result in a quite high profit margin for them if DARPA paid them $2 million for the higher payload air-launched version. Bob Clark

Thanks for the Mockingbird SSTO link. This though did use pump-fed engines. If Sidereus plans pressure-fed then their plan is much more problematical because of heavy tank weight. The pumps Mockingbird used though were piston pumps, since turbo pumps are harder to get to work at small size. The XCOR company showed piston-pump rocket engines are doable since they built them and actually did test flights with them on rocket propelled airplanes: XCOR Aerospace. https://kmhv.wordpress.com/ XCOR went bankrupt but their assets were purchased by a space-education company: Bankrupt Spaceflight Company's Space Plane Assets to Help Young Minds Soar News By Douglas Messier published April 20, 2018 https://www.space.com/40352-xcor-aerospace-lynx-space-plan-stem-education.html Then Sidereous could purchase these engines ready made. Bob Clark

A speculation on a small SSTO based on the Falcon 9 upper stage. Here’s the specifications of the F9 upper stage: The Merlin Vacuum on the 2nd stage can’t operate at sea level because of its high expansion. And the sea level Merlin would not have enough thrust to loft the stage from the ground. So I’ll reduce the propellant load by 1/2. A single sea level Merlin could then launch it. I’ll estimate this half-size 2nd stage’s dry mass by first subtracting off the engine mass from the dry mass, taking half the remaining mass, then adding back on the mass of the engine. The reason is you still need the full engine size and mass to lift off, not a half-size engine. This can only be an estimate of the dry mass since not all components will reduce in size proportionally. But with this estimated dry mass the results are as below: So about 670 kg to orbit as an expendable. For an operational SSTO you really want to use altitude compensation. I estimate using it you could raise the payload to ca. 1,600 kg or possibly higher. Another nice thing about this is you could get 10 of the these small SSTO’s from one Falcon 9, since there are 10 Merlins on the Falcon 9, and the total propellant size on the Falcon 9 of 500 tons amounts to 10 of the small size SSTO’s. So you could buy a single reused Falcon 9 at $40 million, and break it down to 10 of the small SSTO’s at $4 million each. Bob Clark

Bob Clark

From the article: In a shocking announcement this week, the European intergovernmental organization responsible for launching and operating the continent's weather satellites has pulled its next mission off a future launch of Europe's new Ariane 6 rocket. Instead, the valuable MTG-S1 satellite will now reach geostationary orbit on SpaceX's Falcon 9 rocket in 2025. Instead of ESA complaining that someone chose a better product when they offered a poor product, they should instead offer a better product, fully within their capability to do so: Towards a revolutionary advance in spaceflight: an all-liquid Ariane 6. https://exoscientist.blogspot.com/2023/06/towards-revolutionary-advance-in.html Bob Clark

The Centaur V is only 13 meters long, 41 feet: While it is a bit wider than the Space Shuttle’s payload bay at 18 feet compared to the shuttle’s 15 feet, the shuttle’s bay was longer at 60 feet. So a skinnyfied version of the Centaur V with the same propellant mass could fit in a vehicle with a space shuttle sized payload bay. Bob Clark

What I meant was Zubrin was saying an air breather couldn’t do the entire flight to orbit as an SSTO because of the loss of efficiency at the high orbital speeds in the range of Mach 20 to Mach 25 being carried out by the airbreather. At lower Mach values say around Mach 5 to 6 an air breather can offer significant advantages as just the first stage because the ISP is so high in that range. What I’m envisioning is that most of the market won’t need the high payload capacity of the Starship. The launch cost would be reduced so much with airbreathers as the first stage that having payload capacity in the range of say 10 tons would cover most of the market. In other words for most of the market you won’t need a huge airbreather as the first stage to loft an upper stage large enough to get 100 tons to orbit. Once Hermeus is actually flying we’ll have a better idea of how much can be it’s reusability and turnaround time. Bob Clark

ESA official discusses the upcoming in July Ariane 6 inaugural launch: Europe aims to end space access crisis with Ariane 6’s inaugural launch. Frédéric Castel June 24, 2024 https://spacenews.com/europe-aims-to-end-space-access-crisis-with-ariane-6s-inaugural-launch/ He doesn’t think the Starship will be a competitor to the Ariane 6. He also doesn’t think there is currently enough of a European market for reusable rockets yet, though he says reusabilty for European rockets will be important in the following few decades. Bob Clark

It’s just based on the fact the turboramjets are derived from existing supersonic jet engines, which have lifetimes of thousands of hours. The turnaround time estimate too is based on the fact supersonic jet fighters have turnaround times between flights of only a few hours. About the Robert Zubrin analysis, remember he is looking at the SSTO case where an air breathing engine is making the entire flight to orbit. However, here we are discussing whether a hypersonic air breather being used as the first stage with the final stage to orbit being a hydrolox rocket, can cut the cost of spaceflight by being reused thousands of times. Bob Clark

That will happen at the higher scramjet speeds, and even then only for hydrocarbons. Scramjet theoretically could operate beneficially up to say Mach 15. That is to say, if they could be made to operate reliably. Ramjets have been seen to operate at Mach 3.5 to 4. Theoretically they should be able to reach Mach 5.5. That is why the test by Hermeus next year is so important. If they can reach Mach 5.5 even if not used as a first stage for an orbital rocket then it can be used as a hypersonic transport. Instead of 6 hour flights cross-Atlantic or cross-continental USA they could be done in 1 hour. For the business case compared to rockets, such flights would be less costly being able to be reused for thousands of flights and within, say, a one hour reuse time like jet engines, rather than just a few tens of times for rockets and weeks between flights. Bob Clark

On the other hand, a Raptor still did explode on both booster landing attempts. Bob Clark

Musk: "[The hot-gas roll thrusters] got clogged with ice. We're not sure how....The location that we're tapping off the engine [to pressurize the LOX tank] is not pure O2. It's got a little bit of water ice... It's Ox-rich gas". Tim Dodd:" So it's incoming off the turbine side?" Musk "Yea. It's got burnt fuel". Dodd: "Wouldn't it have a little bit of C02 in it too then?" Musk: "Yea....We've improved the ice strainers [ice catchers]. We've improved the valves. Something I think we'll do in the future is move to --for critical valves -- series parallel valves. So any one valve failure ... does not take out the ship's ability to orient itself correctly." Dodd: "Are you avoiding doing a more traditional heat exchanger?... I've never heard of an engine using already combusted ...gas... off the pre-burner." Musk: "Yea...We're pressuring the fuel side with gaseous fuel, and the ox side with mostly gaseous oxygen...It affects our max power, especially on the fuel side.... If we turned off autogenous pressurization on the fuel side, we'd actually be able to get more power out of the fuel pump." Dodd: "[Is ice build up what caused the booster shutdown on IFT-3?]" Musk: "Yea, well, we didn't have enough pressure to start the engines...The full answer is quite complicated." In that Everyday Astronaut video about 27 minutes in Elon talks about the autogenous pressurization system: This is a system that instead of using helium to pressurize the propellant tanks, heats a portion of the propellant to provide the pressurization. But surprisingly rather than using heat exchangers to heat the propellant, the exhaust directly from the pre-burners is used to warm the propellants. Tim Dodd was surprised it was done this way because other times it was done, heat exchangers were used. This appears to be the cause of the recurring problems of clogging of the propellant intakes to the engines they’ve been seeing due to ice developing, since the combustion products include water or CO2 which freeze when contacting the cryogenic propellants. I say again SpaceX is desperately in need of a true Chief Engineer, not someone who dabbles in the field. Can you imagine for example an AI company having as its Chief Technology officer someone who just dabbles in the field of artificial intelligence? Remember, this is not the CEO position here, who might be just a competent manager, this is the person who needs to have a firm understanding and knowledge of all the interconnected technology going on at the company. A true Chief Engineer with decades of experience in the SpaceX industry would have known beforehand that using directly the exhaust products fed into the propellant tanks is a bad idea. Bob Clark

If you're going to the moon, you don't need an orbital depot. Can you give the context where he said this? The Starship HLS for Artemis plan requires multiple refuelings. Does he mean a Starship HLS in orbit would itself be the depot? Bob Clark