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A presentation from Marcus House alerted me to this. If this is redundant, we can eliminate the topic.
Stoke Space: https://www.stokespace.com/
Marcus House, SpaceXStarship Updates, Transporter 6,Stoke Space & A Crazy Future Awaits.....
General Response: https://www.bing.com/search?q=Marcus+Ho … cc79ad39bd
I am sure it has a long way to go, but it is a very interesting set of notions. I like it.
The people doing it are from SpaceX and Blue Origin. I wonder if they can use someone else's 1st stage at first.
Done
Last edited by Void (2023-01-07 10:37:53)
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For Void re new topic ...
Best wishes for success!
This topic seems to have a lot of upside potential!
The animation on the web site you showed us is promising.
Follow up:
Per Google:
All
About 844,000 results (0.60 seconds)STOKE SPACE TECHNOLOGIES, INC. :: Washington (US)
https://opencorporates.com › companies › us_wa
Oct 17, 2019 — Incorporation Date: 17 October 2019 (about 3 years ago) ; Company Type: FOREIGN PROFIT CORPORATION ; Jurisdiction: Washington (US); Branch: Branch ...Stoke Space - Crunchbase Company Profile & Fundinghttps://www.crunchbase.com › stoke-space-technologies
Stoke Space develops reusable rockets to provide the satellite industry with low-cost, on-demand access to and from any orbit. Seattle, Washington, United ...Stoke Space / 100% reusable rockets / USAhttps://www.stokespace.com
We are opening up access to and from orbit with our rockets designed to fly daily.Stoke Space raises $65 million for reusable launch vehicle ...https://spacenews.com › stoke-space-raises-65-million-f...
Dec 15, 2021 — The company, based in the Seattle suburb of Kent, Washington, said Breakthrough Energy Ventures led the round. Several other new investors also ...Articles about Stoke Space - GeekWire
https://www.geekwire.com › tag › stoke-space
Relativity and Reach, Stoke and Starfish: Blue Origin veterans spark space startups · GeekWire Newsletters · Geek Real EstateSee More · Send Us a Tip · Job Listings ...
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For Void re New Topic ...
Here is further follow up by Google ...
I was not surprised to find the name of Bill Gates in the middle of the Wikipedia entry on Break Through Energy, which is helping to finance Stoke.
About 10,100,000 results (0.38 seconds)
Breakthrough Energy Ventureshttps://breakthroughenergy.org › our-work › breakthro...
BEV is an investment firm seeking to finance, launch, and scale companies ...
The BEV Portfolio
The aim of Breakthrough Energy Ventures is to accelerate an ...
BEV Board and Investors
Breakthrough Energy Ventures is a group of investors who are ...
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How big is Breakthrough Energy Ventures?
FeedbackBreakthrough Energy Ventures
https://breakthroughenergy.org
Nov 3, 2022 — Focused on developing and deploying the critical climate solutions our world needs to reach net-zero emissions by 2050.
About BE · Our Work · News · SearchOur Approach | Breakthrough Energy
https://breakthroughenergy.org › our-approach
Focused on developing and deploying the critical climate solutions our world ...Breakthrough Energy Our Team
https://breakthroughenergy.org › our-approach › our-te...
Focused on developing and deploying the critical climate solutions our world ...Our Work | Breakthrough Energy
https://breakthroughenergy.org › our-work
To get to zero, the world needs a comprehensive approach to innovation at ...Breakthrough Energy Ventures - Crunchbase Investor Profile ...
https://www.crunchbase.com › organization › breakthro...
Breakthrough Energy Ventures is an investor-led fund made up of members of the Breakthrough Energy Coalition, guided by scientific and technological ...Breakthrough Energy - Wikipedia
https://en.wikipedia.org › wiki › Breakthrough_Energy
Breakthrough Energy is the umbrella name of several organizations, founded by Bill Gates in 2015, that aim to accelerate innovation in sustainable energy ...Founder: Bill Gates
Founded: 2015; 8 years ago
Headquarters: Kirkland, WashingtonBreakthrough Energy - LinkedInhttps://www.linkedin.com › company › breakthrough-ene...
Breakthrough Energy is dedicated to helping humanity avoid a climate disaster. Through investment vehicles, philanthropic programs, policy advocacy, ...Breakthrough Energy clean energy investment fund launched
https://ec.europa.eu › commission › presscorner › detail
Bill Gates, Chairman of Breakthrough Energy Ventures, said: “Breakthrough Energy Ventures-Europe is a great example of driving innovative ways for the private ...
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Stoke Space joins SpaceX, Blue Origin, RocketLabs, and others on a "fully reusable upper stage" quest. We already have reusable boosters. Stoke Space went from incorporation about 4 years ago to partial stage tests in 2023, using some of the most experienced aerospace engineers from SpaceX, Blue Origin, Firefly, and others. I don't think that's too remarkable, but it's right up there with any other company. It's great that our Space Industrial Complex is building so much experience designing engines and rockets from scratch, though. Given another 2 to 3 iterations of this, we might be able to design / build / launch a fully reusable orbital class rocket inside of 5 years. That would be quite remarkable.
I see the value-add of Stoke Space and similar companies as turning America into a "one-stop-shop" for all things related to rocketry and satellites. Whatever you need, we have it here. Need a satellite launched tomorrow? Can do easy. Want to hitch a ride to Mars? We got you covered. So, your nation wants to send a probe to Jupiter? Yeah, we can do that for you. Send us your payload and we can get it to where it needs to go. That's the real value-added innovation of small companies like Stoke Space.
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Absolutely true kdb512.
I like it that at this point in time we are seeing whole new creations. The companies you have additionally mentioned, are sort of in a family of methods, Dream Chaser is another kind and Stokes space is off in its own evolutionary path.
If I understand, they are able to use a "Ring of Fire" circle of engines to then incorporate the heatshield into a sort of aerospike engine process.
I do notice that they use Hydro Lox on the 2nd stage, which is sort of heritage from Blue Origin. The 1st stage will apparently be Oxygen and Natural Gas.
The ideal coolant for the Heat Shield would be LOX, but very hard to use, with hot metal, I am sure.
Perhaps it will be some other substance. But Hydro lox propulsion, would allow them to get landing resources from the Moon. Oxygen, Hydrogen, water, perhaps Methane from asteroids. Over a long period of time these may be established into a "Supply Chain.
The first dream is that this thing can be made to survive reentry, and landing. But the greater dream is that somehow, in time an engine system can be developed that can utilize the heat of reentry to propulsive brake using the reentry heat, and just maybe even get an assist in landing from it.
For instance, if a tank can take 6 bars pressure, can you fill it with live steam from evaporated water, and use that to land? I am sure they are not up to that with this yet, but over time it may prove true that that could be useful, perhaps for Earth, Venus, Mars, Titan? It is a very tenuous Maybe.
My understanding is that this is a small vehicle, less than 2 tons of cargo, but that is good. It is better to start at that magnitude, and then if it works perhaps, it can be sized up someday.,
Done.
Last edited by Void (2023-01-08 11:13:34)
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A little bit more about Stoke Space: https://www.bing.com/videos/search?q=St … &FORM=VIRE
He does seem to explain to some degree the aerospike characteristics of the upper stage propulsion.
More:
https://www.bing.com/videos/search?q=St … &FORM=VIRE
https://www.bing.com/videos/search?q=St … &FORM=VIRE
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Last edited by Void (2023-01-09 11:21:54)
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You do not want aerospike nozzles on an upper stage. The expansion may be perfect, but the nozzle kinetic energy efficiency is abysmal. That is because of extreme streamline divergence when the backpressure is between about 60,000 feet and vacuum, for any practical chamber pressures. It takes both high expansion ratio and kinetic energy efficiency to confer good performance.
The point where you measure expansion and divergence and thrust is at the last point of contact with the vehicle. For a conventional bell nozzle, that is the exit lip. The observed wide divergence (equal or exceeding slightly 90 degrees) in vacuum occurs downstream of the lip, and therefore does not affect performance. The divergence angle and expansion ratio are set at the exit lip.
For ANY free-expansion design (of which the aerospike is but one example), there is no bell to constrain the stream divergence between the throat and the last point of contact at the aerospike tip. Out in vacuum, the streamlines diverge to just past 90 degrees right at the throat, well before the expansion is completed at the point of last contact with the aerospike tip. That cuts the nozzle kinetic energy efficiency to 50% max, even if there were no other losses.
People have claimed these were more efficient nozzles with perfect expansion from sea level to vacuum. The expansion claim is true, but NOT with high nozzle efficiency. You actually do better with a fixed bell, anywhere above about 60,000 feet, for any practical chamber pressures.
The efficiency claims for free-expansion nozzles from about 60,000 feet out into vacuum are false. They were false decades ago. They are still false today. Despite being made for decades (just to win R&D contracts from the government). Note that no vehicle has ever yet flown into space using a free-expansion nozzle design! I just told you why.
Sorry, but anyone fully conversant with compressible fluid mechanics, who also has any real-world nozzle design and test experience, knows that I am correct. People who still make these claims are actually showing their lack of the requisite knowledge to succeed at designing anything to fly efficiently into space. Unfortunately, there are still lots of them.
GW
Last edited by GW Johnson (2023-01-09 16:14:29)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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GW Johnson,
Thank You for stopping by to give guidance.
The Cruel truth of the universe may someday become things that those who follow may know how to step correctly to dance right.
But I see that you cannot allow me to lead others to foolishness, and I thank you for that.
I will argue that there is a chance that this new approach may have some value. Time will reveal what is and what is not.
I am very sincere in indicating that I want all that is best and thank you for troubling to guide us.
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Hi Void:
The free-expansion nozzle effect has real utility between sea level and about 60,000 feet or thereabouts (not a sharp boundary). It has little utility from about 60,000 feet out into vacuum because of the extreme streamline divergence at the throat far ahead of the spike tip. Much of the flow blasts out more or less sideways, contributing little or nothing to axial thrust. It's just a vector component-at-an-angle thing.
For a design that features air drop from an airplane as the first stage, such would be viable for the airplane propulsion. In point of fact, a lot of jet engine nozzles already employ this effect. You can recognize them by the spike sticking out the back of the nozzle. When the engine pressure ratio conditions are right for it, the nozzle turkey feathers converge to a choked throat, and the spike does the free expansion job for a supersonic exhaust stream at "perfect" expansion.
I would also point out that a lot of folks dealing with vacuum rocket engines use the terminology "optimized for vacuum", which is quite incorrect. A "perfect" expansion into vacuum would have an infinite area ratio with exit expanded pressure (and temperature) of zero. Obviously, you cannot do that (the gases would liquify), but the expansion bell would be impractically enormous, and that is my point.
There are two and only two considerations for vacuum bell design, and either or both can limit your design. (1) It has to fit inside your stage skirt, with enough room to gimbal the engine for thrust vector control. (2) You have to be able to test it on the ground without spending yourself into oblivion, which means open-air static test, near sea level.
When the expanded exit pressure is below the surrounding ambient atmospheric "backpressure", something called "overexpanded", two things obtain: (1) you have a backpressure term in your thrust equation that is negative, reducing thrust (and specific impulse) without any change in engine massflow. (2) If the backpressure of the atmosphere is too high relative to the expanded pressure, the flow inside the bell will shock-separate, upsetting the regenerative and radiative cooling (which cannot be allowed to persist more than a second or so). Both of these severely limit how big an exit bell expansion ratio you can have. Dealing to one or the other (or both) of these limitations is what they really do when they design a "vacuum-optimized" engine. It's not "optimized" at all, it is instead "constrained".
These considerations also interact with engine turndown and with engine ignition. Few rocket engines ever lit successfully at full power. You ignite at reduced power (with separated flow in the bell) and quickly throttle up before the heat transfer troubles destroy your bell. And, you need to stay unseparated in the bell when the chamber pressure and exit pressure are reduced at the lowest thrust setting you intend to use near sea level.
It's just a whole lot more complicated than most folks suspect, I guess.
Folks designing sea level engines can "optimize" to perfect expansion. For a given chamber pressure, there is one area expansion ratio that makes the expanded exit pressure equal to sea level atmospheric pressure. The thrust is the momentum term, because the exit pressure minus backpressure term is zero. That's "perfect" expansion.
When you fly one of these to higher altitudes, the exit pressure exceeds the ambient atmospheric backpressure-at-altitude, which makes the pressure term a positive contributor to thrust. We call that operation "underexpanded". Thrust and specific impulse increase as you gain altitude, but not as quickly as they would if you were able to increase the bell expansion ratio (which is the much stronger effect on thrust via the momentum term).
The greater strength of the momentum term is exactly why so many have pursued free expansion nozzle designs for so many decades, in pursuit of higher performance. It works "right" when the backpressure is significant (sea level to near 60,000 feet). It just always works "wrong" (laterally-directed streamlines) when the backpressures are very low, which obtains from around 60,000 feet on out into space.
As long as the throat is ahead of the expansion surface tip, letting too many streamlines diverge out to the sides, that fatal difficulty will ALWAYS be true! And there is no way to build an aerospike without incurring that situation!
Perhaps some sort of expansion-deflection nozzle might perform better in the thinner air, but those perform more poorly for other reasons, and have not ever been proposed seriously for use.
GW
Last edited by GW Johnson (2023-01-10 10:34:32)
GW Johnson
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"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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It is very generous for you to give your insight. So, it is required that I do respectfully reply.
I think I understand that a 2nd stage of the Stokes device cannot extract much advantage from a virtual aerospike effect on the way up. But I wonder if it could try to get an advantage on the way down to enter the troposphere and land as well.
Keep in mind that I am puzzled about how they do intend to have an aerospike effect at all.
In truth, that aspect of the device is beyond my ability to comprehend with any strength.
But what I do notice about their intentions is to get an aero burn without traditional forms of heat shielding. They intend to use active cooling with a fluid. I presume that the heatshield being metal will have channels in it like a rocket engine.
I do no longer harbor any notions that Bill Gates is a phony. He seems to give backing to this device.
So, I am still interested in the future of this device and will hope to watch it do something.
Perhaps it will be suitable for the "Made in Space" efforts to automatically manufacture materials in microgravity, and then land the capsules.
Such a device may not need to be big to make a lot of bucks, I suspect.
What do you think? I do not demand a reply. If you wish.
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I looked around a bit on their site. The first stage looks an awful lot like a Falcon-9 first stage. We already know that works well. I saw nothing to indicate where they were going to get their LOX-LCH4 engine or engines.
The upper stage looks sort of like the old DC-X vertical-flight rocket idea. That's an alternative to SpaceX's belly-flopping Starship approach. I didn't see much in the way of any aerospike effect. In order to land, these have to be sea level-type bells on these thrusters. They are using fixed-mounted small hydrogen-oxygen "thruster" engines in a ring around the base of the vehicle. Differential throttling is how they intend to do thrust vector control. They'll get more aerospike effect at landing than they ever would on the way to orbit.
I did see in the illustrations on the website the streamline divergence effect depicted for thruster plumes around the extended heat shield. There might be some aerospike effect there, but it will be minimal. There is a long tradition of simply using the LOX-LH2 Isp advantage for overcoming the Isp-deficit of a sea level bell out in space. You can get away with LH2 low density in an upper stage because the propellant quantities are smaller. That's why they are using LNG in the lower stage: it's a denser form of hydrogen, still low, but with better Isp than kerosene.
I could not tell which propellant they are using to cool the metal heat shield. They didn't specify, but I'd bet its transpiration (sweat) cooling. That would create a cloud of vaporized propellant flowing out over the exposed thruster bells, protecting them from direct contact with the entry plasma. Using very small thrusters is a part of making that scheme work. Note however that no one has ever done a liquid-cooled metal heat shield before. It was proposed for experimentation on the old X-20 "Dyna-Soar" that never flew, though.
I can see why Bill Gates might invest in this. It is a promising concept.
GW
Last edited by GW Johnson (2023-01-11 10:39:24)
GW Johnson
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"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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I guess I will take a chance to be wrong, but it occurs to me that Terran-R 1st stage might be about the power of a Falcon 9 1st stage.
It does burn Methane and Oxygen.
So, then there are those who think a Falcon 9 might be able to launch a Dream Chaser.
So, someone clever who was building a Metha lox 1st stage of a certain size might be able to launch their own proposed Mini-Starship, Dream Chaser and a properly sized version of the Stokes 2nd Stage.
I think that would be very big stuff.
Granted, if Starship proper is put into operation, then that can lift a great deal of mass to orbit. 2.0 would lift even more.
But to also have a Falcon 9 sized Metha Lox 1st stage to lift those three I previously mentioned, that would be very nice in addition.
I will also be wondering about the Stokes Ship for Moon activities. What about refilling it in orbit?
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Last edited by Void (2023-01-11 15:47:32)
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Somebody is going to have to learn how to do transfers of cryogenic propellants in zero-gee/vacuum. Nobody has yet done that. The storables hydrazine and NTO have been transferred routinely by the Russians at ISS, but ONLY the Russians so far!
Gaseous transfers to satellite ion thruster systems don't count, still being experimental. And being gas phase.
And the technologies supporting storables transfer do NOT support cryogenic transfer! The propellant ullage problem is the long pole in the tent, and surface tension effects are not going to be the practical solution to it, despite what is used in some upper stages.
GW
GW Johnson
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Well, you are right of course.
I have considered an impeller to separate the liquid from the ullage gas using centrifugal force. Then the ullage gas could be used to pneumatically herd the solid contents towards the impeller, blowing from the opposite end of the tank from the impeller. In my dream world there would be some way to image the process in real time to be sure it is functioning. I realize that that is easy to say, maybe not so easy to do safely.
The progression I hope from about Starship, is to get it to work at all, then get it more reliable, then have it support Starlink, then develop a tanker version. Of course if they are doing Starlink they will be able to launch other things.
But with the Tanker, I would hope that ships like the Stoke Ship and the Mini-Starship might be able to begin missions to the Moon perhaps, round trip.
While there will be Starships to land on the Moon, I might think that some of the other ships could do some science and check resources out on the Moon for a lower budget.
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Last edited by Void (2023-01-12 19:41:12)
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What I came up with may or may not be the ultimate solution. But it is based on centrifugal force.
I would dock the tanker and the recipient end-to end, and spin both up as a single unit, like a big rifle bullet, at a rather modest spin rate. Given appropriate baffles and suction plumbing on the lateral sides, the propellant would fairly quickly form a hollow cylinder on the outer wall, due to centrifugal force as artificial gravity. From there pumping is entirely conventional. No new materials are required.
It's just that somebody actually has to do this a bunch of times, to refine and prove out the process and equipment.
GW
GW Johnson
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Well, it is important that something that can work well will be proposed. Perhaps your notion is the one.
I believe that ULA has intentions towards refilling and that is Hydrogen and Oxygen.
This is a bit old but interesting: https://www.space.com/33297-satellite-r … l-ula.html
I did not notice how they intend to do it but that would be trade secrets, if they have such a secret.
Quote:
As a customer, ULA is willing to pay about $1,360 per lb. ($3,000 per kilogram) for propellant in low Earth orbit. The going rate for fuel on the surface of the moon is $225 per lb. ($500 per kg), Sowers said. In talking with asteroid-mining experts, ULA would take delivery of propellant at L1 for $450 per lb. ($1,000 per kg), he said.
"Having a source of propellant in space benefits anybody going anywhere in space, to be honest," Sowers said. "What excites me is that, once you have the propellant capability going, you make a lot of other business plans look a lot better, be they on the moon, at L1, or other places."
Of course, that was 2016 or there abouts, and I suppose it is outdated vapor ware by now, but maybe the new vapor ware is better!
So, I think I have noticed that it is possible that in the future Hydrogen/Oxygen propulsion might at times push Methane/Oxygen ships around and vice versa.
I don't precisely see how that would work out, but I think it is a possibility.
From what I can gather, Methane/Oxygen is the preferred method now for 1st Stages flying from Earth or SSTO from Mars.
Dealing with the Moon though it may be the Hydrogen/Oxygen stays the plan.
To me it suggests a Starship that goes to Lunar Orbit but does not so often land, and the use of Hydrogen/Oxygen Stokes as a transfer method, and Centaur possibly to assist Starships exit from the Moon back to the Earth. If SpaceX succeeds with the landing tower method, they are trying then Starships would not have legs at all, except for cases where they might land on the Moon.
At this moment, it does look like the Terran-R 1st stage might lift Dreem Chaser, Terran-R 2nd Stage, and maybe the Stokes Ship.
But Vulcan might be able to do that as well.
New Glen might show up some day after some time. Its build methods are very different than the others, so if Jeff Bezos continues to want to it can keep trying.
Done.
Last edited by Void (2023-01-13 09:54:52)
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There's been a weirdly-overlapping boundary between low orbit capabilities, and capabilities to go elsewhere, for many decades now. All of the nonreusable launch vehicles, and even some semi-reusable things today, can send significant payloads to low orbit. Unrefueled, and flown with much smaller payloads, they could also go elsewhere. It costs a whole lot more to go to highly-elliptical high orbit about the Earth than it does low eastward circular.
But it costs very little more than that to go to the moon one-way, or even further one-way, like Venus or Mars. The problem always was very much smaller payload to the higher energy missions. It still is.
To break that impasse, one either had to use much more gigantic launch vehicles, or refuel them in low eastward circular orbit, or both! And when you talk about return trips, the payloads get really, really big. Or else you have to make refueling propellant there. Or both.
That's just the nature of the problem. Complicated.
Multiple outfits are now addressing the reusable first stage problem. SpaceX has been the first to attempt addressing the reusable upper stage problem to low Earth orbit with its Starship, but NOT with its Falcons. That reusable upper stage problem is a very much tougher problem to solve, than the lower stage problem. That's why they never developed a reusable Falcon upper stage.
Once again, the biggest first step is getting back from low circular eastward Earth orbit, versus getting back from any of those other higher-energy missions. As it turns out, the physics of entry at only 8 km/s allows either ablative heat protection, or re-radiating refractories that do not ablate. It may yet prove possible to do metals cooled by transpiration cooling, we don't know yet.
But for the higher-energy missions, entry is nearer 11 km/s or higher, and only ablatives are known to work as solutions. None of those will be usable more than once or maybe twice, certainly only a single handful of times, even if carbon-carbon composite. That does not offer much prospect of reusability in the sense of only occasional refurbishment.
I've seen some of the new super-ceramics with the extremely-high melt-points touted as the solution to that problem, but that's quite mistaken! Those are all high-density, high-thermal-conductivity items, and will soak out during exposures to a near-isothermal condition at a really high temperature. So there will be no way to hang onto it! And if you cannot hang onto it, what good does it do you as a heat shield? I've seen no answers to that question. None.
The technology does not yet exist to make these super-ceramics in a low-density form with internal void spaces. But if it did exist, these would be low thermal conductivity, and they would behave very far from isothermal during heating exposures. Those you could hang onto as a heat shield. But the internal voids and low density also inherently make the material strength low! Such will always be fragile, just like shuttle tile was. But that low density thing was exactly what made shuttle tile functional as a heat shield that one could hang onto!
The problem with alumino-silicate shuttle tile wasn't so much the 3250 F melt-point, it was the 2250 F solid phase change point that caused shrinkage by about 3% and extensive shrinkage-cracking! That is where the only-2000 F temperature limitation for shuttle tile came from, and which in turn restricted it to low eastward circular Earth orbit missions. And it had to be black on the windward side, where heating was higher, in order to re-radiate efficiently. And it was still inadequate for stagnation heating on the nosetip and leading edges (those were carbon-carbon, replaced every few flights).
Find a way to make low-density forms of the super-ceramics with internal void structure, but with a far-higher temperature restriction, and you have found a way to make non-ablating refractories that might do higher-energy entries. The next problem to solve is at what speed the plasma goes opaque to infrared radiation, cutting off the ability to cool by re-radiation. At that point, you will have to actively-cool the material in some way, with a sacrificial liquid. I'm not sure, but I think that is about 10 km/s, where plasma radiation heating starts to dominate over convective heating.
There's a lot of complicated physics involved with such an endeavor. I hope I have provided a guide to what might be, and what might not be, possible.
GW
Last edited by GW Johnson (2023-01-14 15:26:33)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Somehow I, up until now overlooked your guidance in the last post. I think I will pin your post to my special library. Thank You.
I did come here about the Dream Chaser. I searched for that, and did not get a specific topic.
I have a little "News", somewhat interesting, kind of iffy, making me wonder, but in a good way.
That is not it. I am beginning to hate Bing, as I find things on my phone and cannot fetch them to my computer with Bing.
Anyway, there is mention of the cargo variant which we hope will become a crewed variant, and those are in the 100 series of numbers, but they suggest a rigid wing variate with the numbering of 201.
But that is not much to go on. I really hope that they keep going with this device and it's spinoffs.
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Last edited by Void (2023-01-18 21:08:25)
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GW,
After achieving orbit, you can then use photovoltaics and electric propulsion to deliver significant payloads to other places in the solar system. You can affordably get satellites and cargo to other planets rather quickly (assuming low-cost propellants are used), relative to chemical propulsion, especially if you have a fully reusable launch vehicle with a turn-around-time of a week or less. If we're talking about missions with humans, then you either need lots of shielding or a giant chemical propulsion rocket to leave Earth quickly to avoid the Van Allen Belt radiation. Since you require shielding anyway, I would opt for lots of shielding over lots of propellant.
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Something more: From the Everyday Astronaut: https://everydayastronaut.com/stoke-space/
A video included.
Really helpful. I hope they pull it off. Seems to me we could hope for a SSTO version for Mars, this prototype works.
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Last edited by Void (2023-02-04 12:08:38)
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https://www.teslarati.com/stoke-space-s … mpetition/
Quote:
Stoke Space to build SpaceX Raptor engine’s first real competitor
So, I guess it helps knowing that it can be done. And to some degree, I am guessing they will know something of how it is done.
So, I guess as it will be smaller, then this device may as a 1st stage be similar to Terran-R.
The 2nd stage though is a whole nother creature not exactly a Mini-Starship.
I want all contenders to succeed and to continue though time to develop their talents.
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Last edited by Void (2023-02-08 10:06:10)
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This is probably redundant to my previous posts, but maybe new people here would be interested: https://www.bing.com/search?q=How+Stoke … a84fd82e53
https://www.bing.com/videos/search?q=Ho … &FORM=VIRE
I really want to see if they can make it work.
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Last edited by Void (2023-02-19 10:16:14)
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For Void.... your Bing search produced so many results I thought you might not mind if I post just one link ...
https://www.stokespace.com/everyday-ast … oke-space/
This video looks promising for coverage of the concept of Stoke Space... the animations are helpful, and the on-ground shots show work in progress.
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There's been a weirdly-overlapping boundary between low orbit capabilities, and capabilities to go elsewhere, for many decades now. All of the nonreusable launch vehicles, and even some semi-reusable things today, can send significant payloads to low orbit. Unrefueled, and flown with much smaller payloads, they could also go elsewhere. It costs a whole lot more to go to highly-elliptical high orbit about the Earth than it does low eastward circular.
But it costs very little more than that to go to the moon one-way, or even further one-way, like Venus or Mars. The problem always was very much smaller payload to the higher energy missions. It still is.
To break that impasse, one either had to use much more gigantic launch vehicles, or refuel them in low eastward circular orbit, or both! And when you talk about return trips, the payloads get really, really big. Or else you have to make refueling propellant there. Or both.
That's just the nature of the problem. Complicated.
Multiple outfits are now addressing the reusable first stage problem. SpaceX has been the first to attempt addressing the reusable upper stage problem to low Earth orbit with its Starship, but NOT with its Falcons. That reusable upper stage problem is a very much tougher problem to solve, than the lower stage problem. That's why they never developed a reusable Falcon upper stage.
Once again, the biggest first step is getting back from low circular eastward Earth orbit, versus getting back from any of those other higher-energy missions. As it turns out, the physics of entry at only 8 km/s allows either ablative heat protection, or re-radiating refractories that do not ablate. It may yet prove possible to do metals cooled by transpiration cooling, we don't know yet.
But for the higher-energy missions, entry is nearer 11 km/s or higher, and only ablatives are known to work as solutions. None of those will be usable more than once or maybe twice, certainly only a single handful of times, even if carbon-carbon composite. That does not offer much prospect of reusability in the sense of only occasional refurbishment.
I've seen some of the new super-ceramics with the extremely-high melt-points touted as the solution to that problem, but that's quite mistaken! Those are all high-density, high-thermal-conductivity items, and will soak out during exposures to a near-isothermal condition at a really high temperature. So there will be no way to hang onto it! And if you cannot hang onto it, what good does it do you as a heat shield? I've seen no answers to that question. None.
The technology does not yet exist to make these super-ceramics in a low-density form with internal void spaces. But if it did exist, these would be low thermal conductivity, and they would behave very far from isothermal during heating exposures. Those you could hang onto as a heat shield. But the internal voids and low density also inherently make the material strength low! Such will always be fragile, just like shuttle tile was. But that low density thing was exactly what made shuttle tile functional as a heat shield that one could hang onto!
The problem with alumino-silicate shuttle tile wasn't so much the 3250 F melt-point, it was the 2250 F solid phase change point that caused shrinkage by about 3% and extensive shrinkage-cracking! That is where the only-2000 F temperature limitation for shuttle tile came from, and which in turn restricted it to low eastward circular Earth orbit missions. And it had to be black on the windward side, where heating was higher, in order to re-radiate efficiently. And it was still inadequate for stagnation heating on the nosetip and leading edges (those were carbon-carbon, replaced every few flights).
Find a way to make low-density forms of the super-ceramics with internal void structure, but with a far-higher temperature restriction, and you have found a way to make non-ablating refractories that might do higher-energy entries. The next problem to solve is at what speed the plasma goes opaque to infrared radiation, cutting off the ability to cool by re-radiation. At that point, you will have to actively-cool the material in some way, with a sacrificial liquid. I'm not sure, but I think that is about 10 km/s, where plasma radiation heating starts to dominate over convective heating.
There's a lot of complicated physics involved with such an endeavor. I hope I have provided a guide to what might be, and what might not be, possible.
GW
SpaceX is reportedly dissatisfied with their ceramic heat shield tiles specifically with their becoming dislodged during ground static firings and therefore likely also during actual launchings. It appears the first test launches will not even have them, so the Starship will be expendable then.
Have you considered informing them of the high temperature ceramic you worked on? I discussed it here:
Altitude compensation attachments for standard rocket engines, and applications, Page 6: space shuttle tiles and other ceramics for nozzles. UPDATED: 3/6/2018.
https://exoscientist.blogspot.com/2017/ … s-for.html
By the way, you worked on this ceramic for insulation for ramjets. What do you think of my proposal in that blog post to use lightweight ceramics such as the shuttle tile ceramics or your ceramics for lightweight nozzle extensions?
The long vacuum nozzle on the Star 48B upper stage solid weighs nearly as much as the rocket motor casing. And the long nozzle extension put on the highest Isp version of the RL10 engine doubles the dry mass of the engine from 150 kg to 300 kg.
Robert Clark
Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):
“Anything worth doing is worth doing for a billion dollars.”
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Hi Bob:
Thee are a couple of things to understand about using my weird ceramic as a combustor or nozzle material. The stuff has about the strength as well as the density of commercial higher-density styrofoam. It has to be contained or held in some way to be successful. The cooling method in the ramjet (or a rocket) is not re-radiative. It is by conduction to the containing shell. It reduces the conductive heat flow by maintaining a very high thermal gradient through the material. The hot surface merely sees itself on the other side of the nozzle, not any sort of low temperature heat sink environment, which equilibrium cuts off all thermal re-radiation.
The thermal shrinkage cracking does not extend all the way through the material, for this kind of application, because part of the material stays cold, and after the burn, the hottest temperatures of the moving thermal wave fall below the phase change point, before the wave can reach the cooler portions. Thus the cracks matter little, especially since the material is contained within the shell. The weakening induced by the cracks is offset by the shell containment. And I used no bond, only a mechanical retention inside a cylindrical shell.
In the burner I tested, flow was largely subsonic, and reached sonic speed only at the throat. Even if I had used a convergent-divergent shape, any supersonic Mach number would have been very modest. Thus the wind pressures tearing at the shrinkage cracks were quite low.
Used as a really supersonic rocket nozzle, or as a vehicle heat shield, the wind pressures tearing at shrinkage cracks would have been very high. So they could not be allowed. That means hot face temperatures could not be allowed to exceed 2300 F. Contained, I could allow right up to melting, at about 3300 F. Even so, at my ramjet conditions, that still severely restricted the hot gas temperatures I could tolerate to about 3800 F or thereabouts. One would still want to do redundant retention if not fully contained by a shell, something inherent in the heat shield application. Re-radiation limits the hot face temperature in the heat shield application. So one would have to "glom onto" the reinforcing fabric with the supporting panel, plus use a ceramic cement to bond the insulation to that panel. That is what I presented as a possibility.
I did check with the manufacturer of the materials I used long ago. They are still available by special order, and he said I could add carbon black to the ceramic cement I used as a surface porosity-sealant. Blackening that surface is how I calculated the ability to survive stagnation heating rates at under 2300 F re-radiating temperature, but for rather large "nose" radii only! Unlike Spacex's "Starship", my spaceplane designs had to have virtually-flat bottoms to get the stagnation heating low enough for my ceramic to survive it at 8 km/s entry speeds. Peak heating is about half to 3/4 of the way down from entry interface, at speeds nearer Mach 10, than Mach 25 at entry.
To use this stuff as the supersonic expansion cone liner of a rocket nozzle in space, you would have to cool the shell that contains it. That might not require cryogenic liquids as the conduction heating rate into that shell would be quite low. But I rather doubt my specific material would survive anywhere near the throat, as rocket hot gas temperatures are simply far too high. The hot face temperature of the material would get far too high. One of the new super-ceramics, done as a low density material (something not yet possible), might serve as such. But probably not my oddball aluminosilicate.
I'm pretty sure it was my curing method that got me the porosity and low density. This stuff is a water drive-off "cure", but normally one doesn't cure it above the boiling point. So it is normally a much higher density. I cured it in an oven at about 215-220 F, and I believe the water flashing into steam and wormholing its way out of the material, is what gave me the porosity and low density. Had I not gotten that, it would not have worked as a combustor insulator.
GW
Last edited by GW Johnson (2023-03-31 09:08:06)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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