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#1 Re: Human missions » Starship is Go... » Yesterday 08:44:00
Robert Zubrin again presents the argument a Starship Mars mission would be better implemented by using smaller lander stage to do the actual landing rather than the Starship itself:
The flaws in Musk’s Mars mission
Our future lies on the Red Planet.
Robert Zubrin
April 1, 2025 6 mins
Furthermore, it needs to be done correctly. SpaceX’s Starship, which claims to be the world’s most powerful reusable launch vehicle, promises to be a terrific asset. But Musk insists that it should be the only vehicle used for the mission. While a Starship upper stage could be refuelled on orbit by tanker Starships, enabling it in theory to fly from Earth orbit to Mars, its 100-tonne mass makes it suboptimal for use as an ascent vehicle. It would make far more sense to develop and use a similar but much smaller vehicle — a “Starboat” if you will — to travel between the surface of Mars and its orbit. Starship plus Starboat could enable highly efficient missions to Mars. But this will require a programme leadership capable of speaking truth to power.
https://unherd.com/2025/04/the-flaws-in … s-mission/
Bob Clark
#2 Re: Other space advocacy organizations » NSS Houston Chapter Events » Yesterday 07:31:59
What's on the agenda for the April meeting?
Bob Clark
#3 Re: Interplanetary transportation » VASIMR - Solar Powered? » 2025-03-28 16:18:13
Several thin-film solar cell research efforts have come up with better than 1kW/kg power density solar cells, the power density needed for VASIMR. The highest one I’ve seen is this:
Solar-cell-packin' drone uses sunlight for on-the-spot recharging
By Ben Coxworth
April 19, 2024
Created by scientists at Austria's Johannes Kepler University Linz, the lightweight, flexible cells are made of a semiconductor material known as perovskite, and they're less than 2.5 micrometers thick – that's just 1/20th the width of a human hair. And importantly, they're 20.1% efficient at converting sunlight into electricity, plus they boast a power output of up to 44 watts per gram.
In a proof-of-concept test of the technology, the scientists mounted a ring-shaped array of 24 of the cells on a commercially available CX10 miniature quadcopter, which was dubbed the Solar Hopper. The array made up just 1/25th of the augmented aircraft's total weight, with the cells themselves making up only 1/400th.
https://newatlas.com/drones/solar-cells … -sunlight/
It is notable though that last sentence in this passage suggests the structural elements make up the greatest component of the weight. Still, being out of the Earth’s gravity and at very low acceleration for our application, the structural elements would be much reduced.
Bob Clark
#4 Re: Human missions » Starship is Go... » 2025-03-27 14:38:40
New high temperature ceramic heat shield material promoted to SpaceX to solve their heat shield problems:
AN OPEN LETTER TO ELON MUSK.
Dr. Ed Pope
https://www.linkedin.com/feed/update/ur … 4910300160
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/ma … composites
GW, perhaps you should pitch your high temperature ceramic directly to SpaceX.
Bob Clark
#5 Re: Interplanetary transportation » With commercial heavy launch: point-to-point rocket transport. » 2025-03-24 14:21:22
The Air Force is planning on funding point-to-point rocket cargo transport:
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_p … 26030.html
Bob Clark
#6 Interplanetary transportation » With commercial heavy launch: point-to-point rocket transport. » 2025-03-22 16:06:47
- RGClark
- Replies: 4
Implications of the coming era of commercial heavy launch: point-to-point transport for both cargo and passengers.
https://exoscientist.blogspot.com/2025/ … ra-of.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.
In my blog post I argue that SpaceX already has this capability for such low cost launch 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.
Bob Clark
#7 Re: Human missions » Starship is Go... » 2025-03-21 17:58:20
Another expert engineer criticizes the multi-refueling approach SpaceX is taking to get to the Moon and Mars as a bad approach, 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/kevinholde … -and-mars/
Bob Clark
#8 Re: Human missions » Starship is Go... » 2025-03-21 01:57:45
Actually, I have given examples where Elon ignored basic principles of spaceflight engineering. The flame trench fiasco is one of many:
Read over those comments by Robert Zubrin I linked in post #2019. That he makes this point so vociferously suggests it’s because it’s basic spaceflight engineering being ignored: to get to high delta-v destinations use staging.
Bob Clark
#9 Re: Human missions » Starship is Go... » 2025-03-20 14:27:41
Dr Clark,
All the personal attacks against Elon Musk, for whatever your personal motivations happen to be, won't solve a thing.
It’s not personal. It’s purely engineering. It’s literally basic spaceflight engineering that Elon is ignoring. No true Chief Engineer would ignore such principles. Basic principles in engineering are being repeatedly ignored by Elon. SpaceX has many very good engineers. But Elon repeatedly ignores their recommendations.
That is literally the only reason why Starship is not already delivering high payload mass to orbit.
If you read any of the biographies of Elon a common feature that emerges is Elon is brutal in firing those who he feels their engineering is not up to the job. He can’t see that he is that person now.
Bob Clark
#10 Re: Human missions » Starship is Go... » 2025-03-20 08:38:31
…
This thrust oscillation in the Raptor-3's is large enough that I consider it "combustion instability". At the old rocket plant, we never allowed a design out the door with oscillations that large.
GW
There’s no telling if this will ever be solved with Musk serving as Chief Engineer. Look up ‘hubris’.
Bob Clark
#11 Re: Human missions » Starship is Go... » 2025-03-20 08:33:13
Another article discusses this critical review of Will Locket and also the opinion of Robert Zubrin that SpaceX is taking the wrong approach in wanting to land the entire Starship on the Moon or Mars:
Mini-Starship or bust? Experts clash over SpaceX’s future.
https://floridamedianow.com/2025/03/spacexs-future/
As Zubrin notes, standard spaceflight engineeering says you add an additional, smaller upper stage to do high delta-v destinations. Zubrin has made this point numerous, numerous times:
https://x.com/robert_zubrin/status/1374 … 00896?s=61
https://x.com/robert_zubrin/status/1725 … 79000?s=61
https://x.com/robert_zubrin/status/1278 … 20833?s=61
https://x.com/robert_zubrin/status/1256 … 45728?s=61
https://x.com/robert_zubrin/status/1256 … 18819?s=61
https://x.com/robert_zubrin/status/1256 … 25249?s=61
https://x.com/robert_zubrin/status/1192 … 85987?s=61
https://x.com/robert_zubrin/status/1192 … 15552?s=61
https://x.com/robert_zubrin/status/1192 … 24192?s=61
https://x.com/robert_zubrin/status/1178 … 41184?s=61
https://x.com/robert_zubrin/status/1127 … 78464?s=61
https://x.com/robert_zubrin/status/1127 … 68961?s=61
And finally,
Robert Zubrin @robert_zubrin
Starship can revolutionize Earth to orbit. But for landing on the Moon or Mars we need to stage off it. Using Starship as a lunar lander is like using an aircraft carrier for white water rafting.
https://x.com/robert_zubrin/status/1178724273025933312?
Zubrin has also argued this directly to Musk and Musk has always stubbornly refused it. Stunning when you think about it, but the development problems with the Starship could be solved with one simple, and I say obvious, move: hire a true Chief Engineer to lead the development. But Musk is too close to it to see that he is the problem.
Bob Clark
#12 Re: Human missions » Starship is Go... » 2025-03-18 08:00:42
“Angry Astronaut” discusses a critical review article of the Starship that claims it can’t be made to work:
Engineer claims that SpaceX Starship can't be fixed! Is he right?
https://www.youtube.com/live/CxEcTXTgiM … sl-0yQVCmi
(There is an audio glitch at the beginning of 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 … 3bf809539c
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 ton 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
#13 Re: Human missions » Starship is Go... » 2025-03-13 06:54:57
NSF - NASASpaceflight.com
@NASASpaceflight
Interesting: SpaceX is looking to hire a Propulsion Systems Engineer, responsible for designing, analyzing, and building feedline system to feed Raptor engines on Starship.
https://boards.greenhouse.io/spacex/job … 607806002…
https://x.com/NASASpaceflight/status/18 … 5587286458
Repeated engineering failures stem from the top. First, 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
#14 Re: Human missions » Starship is Go... » 2025-03-10 09:34:12
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/scie … -musk.html
Repeated engineering failures stem from the top. SpaceX needs a true Chief Engineer making the engineering decisions.
Bob Clark
#15 Re: Science, Technology, and Astronomy » Fusion power in the offing? » 2025-03-04 08:41:56
One thing that is clear for all of the proposed approaches to fusion power is that scale matters. The reason is simple. One of the inputs into the lawson criterion is average confinement time.
https://en.m.wikipedia.org/wiki/Lawson_criterionConfinement time increases as the size of the system increases. Ions escape through surfaces. As scale increases, the ratio of surface area to volume decreases. And it takes more time for an ion to cross a larger confinement radius. This tells us that for any fusion system, technical viability improves as systems scale up. For inertial confinement systems, to meet the lawson criterion the following condition must be met:
Plasma density x compressed radius > 1 gram / cm2.
But there are obvious problems with achieving this in real life. Doubling the diameter of a pellet or magnetic confinement chamber, increases plasma volume by a factor of eight. That increase in size implies increased capital cost and there is a limit to what can practically be afforded. There are also limits to the size of a powerplant that can be accomodated within a national grid. A 10GWe fusion reactor would be a very difficult addition to most grid systems.
Maybe a solution to this problem is improved transmission. HVDC would allow a single unit to serve a larger geographic area.
An amusing approach to the Lawson criterion: Lorentz contraction. Many think of Lorentz contraction as relative, that is, things only appear to shrink as they go faster. This is the case in relativity theory as long as both are traveling inertially, i.e., without acceleration. However, if one is accelerated then the Lorentz contraction is absolute, i.e., both the at rest body and the accelerated body both agree that the accelerated one has shrunk.
Length Contraction is NOT an Illusion!
https://m.youtube.com/watch?v=TxW6_E3uLuo
The situation is analogous to the twin paradox: if motion and time are relative why is it the moving twin ages more slowly? The difference is the moving twin in returning to the starting point was accelerated thus underwent actual time dilation: both he and the at rest twin agree the moving twin had his time slowed.
So whatever the factor needed for the Larsen criterion to reach sustained fusion, accelerate the target plasma at the required relativistic speed, like in atomic accelerators, so the Lorentz gamma factor equals that.
Amusingly, this might be testable in small university or even amateur labs since small accelerators such as Van de Graaff accelerators exist.
Bob Clark
#16 Re: Interplanetary transportation » Could Blue Origin offer its own rocket to the Moon? » 2025-02-21 10:55:49
There is much handwringing at NASA as it appears the Artemis missions will be cancelled. However, in point of fact we are now at a point in the development of spaceflight that manned lunar missions can be mounted for what we are now spending just for flights to the ISS, as long as they are commercially financed.
Then we now have the capability to be at the long-desired position of having a sustained, habitable presence on the Moon:
Could Blue Origin offer its own rocket to the Moon, Page 2: low cost crewed lunar landers.
https://exoscientist.blogspot.com/2025/ … ocket.html
As part of the calculations I came to a surprising conclusion, the production cost, as opposed to the price charged to a customer, for a manned space capsule might be only a few ten's of millions of dollars.
Bob Clark
#17 Re: Human missions » Starship is Go... » 2025-02-14 15:10:36
Anomaly at end of Starship long duration static test?
SpaceX @SpaceX
The extended firing tested new hardware and cycled the six Raptor engines through multiple thrust levels to recreate different conditions seen within the propulsion system during flight. Data from the test will inform upgrades to the ship’s hardware and flight profile ahead of the next launch.
https://x.com/spacex/status/1889799440652763145?s=61
BUT:
Zach Golden @CSI_Starbase
Synchronizing the audio from this video answers a few questions.
It does not sound like there was a single engine relight after shutdown as some have suggested. Instead there is an audible pop that is accompanied by a quick flash.
https://x.com/csi_starbase/status/18895 … 22976?s=61
TheSpaceEngineer @mcrs987
mystery popping components are my favorite
https://x.com/mcrs987/status/1889517378704154850?s=61
The flames were seen coming out of the flap hinge of Starship in IFT-7 at about 7 minutes into flight:
https://x.com/csi_starbase/status/18800 … 56706?s=61
Given stage separation is about 3 minutes into flight, the flames were seen about 4 minutes after the ship’s engine ignition. A test should go at least that far, though ideally all the way to the 6+ minute burn time of the ship. If it requires additional nitrogen and water supplies being added to the test stand, then so be it.
Also, a greenish tinge seen in this clip from the exhaust just for a moment at the start of the clip is a hallmark of copper burning:
https://x.com/mcrs987/status/1889517378704154850?s=61
Bob Clark
#18 Interplanetary transportation » Could Blue Origin offer its own rocket to the Moon? » 2025-02-01 10:37:53
- RGClark
- Replies: 3
Estimates of the propellant load on the New Glenn commonly are in the range of 1,150 tons. However, making a comparison of the size of the tanks to those of the Superheavy booster it’s capacity could be estimated as 1/2.6th that of the Superheavy:
(Credit: Ken Kirtland)
https://x.com/kenkirtland17/status/1761 … 11916?s=61
Since the maximum capacity of the Superheavy tanks is ca. 3,600 tons, the New Glenn booster tanks can be estimated to have a maximum capacity of 3,600/2.6 = 1,380 tons.
With tanks filled to this maximum capacity though it would need higher thrust to lift-off. Given the thrust upgrades already planned by Blue Origin for New Glenn, running a delta-v calculation suggests it could get in the range of ca. 100 tons to LEO, a Saturn V class launcher.
But 100 tons to LEO, i.e., Saturn V class, is commonly given as the launch capacity needed for a Moon rocket. Then New Glenn could possibly serve as a single launch Moon rocket.
Remarkably, Blue Origin as soon as next month in March plans to launch a lunar cargo lander to the Moon, the Blue Moon Mk1. At ca. 21 ton mass and 3 ton payload capacity, this could actually serve also as a manned lander if given a 3 ton crew module. The far larger Blue Moon Mk2 multi-billion dollar manned lander would be unnecessary.
Could Blue Origin offer it’s own rocket to the Moon?
https://exoscientist.blogspot.com/2025/ … ocket.html
Bob Clark
#19 Re: Human missions » Starship is Go... » 2025-01-28 15:09:23
Is SpaceX being fully forthright on the reliability of the Raptor?
1.)A Raptor actually exploded on IFT-4. But SpaceX has not “come clean” on that.
2.)Elon Musk’s explanation of the Starship explosion on IFT-7 raises the possibility the large plumes seen shooting up during the Superheavy landing burns were due to engine bay fires.
3.)SpaceX told the FAA the Superheavy would tip over and float after ocean landing. Instead they always exploded.
4.)The Raptor has to do 3-burns for reusability, but SpaceX hasn’t tested this a single time at full mission burn times, wait times, and power levels.
5.)For these reasons, the FAA should require SpaceX to release any and all videos of the engine bays of both stages while the engines are firing, most specifically during restarts:
The SpaceX Raptor engine is still of unproven reliability.
https://exoscientist.blogspot.com/2025/ … ll-of.html
Bob Clark
#20 Re: Science, Technology, and Astronomy » $2 million prize for a personal flying machine. » 2025-01-28 08:12:35
I found pages that describe the Phase I and Phase II winners. I haven’t found the Phase III winners:
Boeing GoFly winners unveil exotic personal flying machines
We're way, way beyond jetpacks now.
https://www.cnet.com/science/boeing-gof … -machines/
Go Fly’s Phase II Winners
by DEAN SIGLER on 04/19/2019
http://cafe.foundation/blog/go-flys-phase-ii-winners/
Bob Clark
#21 Re: Human missions » Starship is Go... » 2025-01-20 11:17:06
GW-
According to various reports I've seen, the BO BE-4 engines are running at about 80% of their design pressure limits to extend their lifetimes; so--that accounts for the lower performance and lots of fuel burn overcoming gravity in the early stages of flight. I suspect that they will need to increase the chamber pressures to take advantage of the undoubtedly better performance (which IS available) needed in later flights.
Do you have a source for that? If Blue Origin wants to increase their payload to the planned 45 tons, they’ll need to increase the thrust.
Bob Clark
#22 Re: Human missions » Starship is Go... » 2025-01-20 11:15:00
Agree or disagree: it was a mistake for SpaceX to follow the failed Soviet N-1 approach to testing Starship. A Raptor failed both on the booster and on the ship, and on the ship one failed catastrophically. How many total test flights needed now just to make orbit with high payload? 10? A dozen? How many total to prove Raptor reuse reliability? 15? How many total to prove orbital refueling? 20?
In contrast standard industry practice is to construct a separate, full test stand to do full up, full thrust, full duration testing. Done this way at least Starship could be doing expendable flights already by now, and with paying customers. Even Raptor reuse reliability could have been tested on the full test stand, providing a faster route to Starship reuse.
Bob Clark
#23 Re: Interplanetary transportation » Key advance in solar sails for searching for interstellar life. » 2025-01-05 11:10:25
For slowing down it might be Robert L Forwards idea of reflecting back the light from the main sail to a smaller sail would allow you to slow down the smaller sail to stop at the destination.
A problem though is Dr. Forward intended this for the case of laser propulsion where the reflected light could be focused onto the receiving sail. This might not work for the non coherent light from the Sun.
However, actually for the solar gravitational lens case it still works as long as you are on a line extending out from the SGL so you may not need to slow down for that case.
In that Robert L. Forward conception of using reflected light from the main sail to slow down a smaller sail at the destination, he also included the possibility of using the same method to actually *return* from the far destination. Imagine getting returned samples from ‘Oumuamua, the Jovian and Saturnian moons, and Pluto!
However, there is that sticking point in using this method in the case we’re considering here. Forward was imagining it for laser propelled propulsion. In that case you can focus the reflected light that is coherent and collimated. But for our scenario we’re using solar light which will be non coherent and uncollimated. It may not be possible to get the highly focused light at long distances in this scenario. It might be we can carry a laser to do it but that may be too heavy. There may be other light weight methods to do it.
An intriguing possibility: IF it did work, then could it be used to do staging by sending focused light from the main sail *forward* to a smaller sail ahead of it? Then we could increase the speed multiple times by doing multiple staging.
Bob Clark
#24 Interplanetary transportation » Key advance in solar sails for searching for interstellar life. » 2024-12-28 14:37:06
- RGClark
- Replies: 2
The Parker Solar Probe recently survived its closest flyby of the Sun at only 0.04 AU.
This gives confidence that the proposal to achieve high speed of a solar sail using a close flyby of the Sun using the ultralight, but high temperature material aerographite can work:
Interstellar Sails: A New Analysis of Aerographite
by Paul Gilster | Sep 27, 2023 | Sail Concepts |
https://www.centauri-dreams.org/2023/09 … rographite
Such a solar sail could reach a speed of 2%c, 6,000 km/s, using this close flyby. At this speed it could reach the solar gravitational lens(SGL) at 550 AU in only 6 months, and ‘Oumuamua in only 11 days(!)
The implications are stunning. Aerographite is an existing material. Then this means we currently have this capability.
Telescopes placed at the solar gravitational lens(SGL) would have the ability to amplify the images of an Earth-sized exoplanet by 100 billion times. It could resolve continent-sized features on such a planet.
‘Oumuamua is an interstellar object whose unusual motions led some to speculate it could be of artifical origin.
Then we now have the capability to directly observe Earth-sized exoplanets in other star systems and to determine features on an interstellar object that came into our solar system which may have been artificially produced.
Bob Clark
#25 Re: Meta New Mars » GW Johnson Postings and @Exrocketman1 YouTube videos » 2024-12-13 16:56:57
The links work fine.
But if you read the article, you see that I did not do this study for using a tug with Artemis-2 in any way. NASA is going to fly that one with the bad heat shield, that much is clear.
Actually, since the Orion capsule is not reusable, I don't see much usefulness for trying to slow it into orbit coming back from the moon or anywhere else. It'll have a "fixed" heat shield from Artemis-3 onward, and the odds favor success flying with the bad one on Artemis-2, although the probability of a fatal burn-through is not as close to zero as it ought to be.
I did the study to find out what might be possible in the near term. For the orbital data I used, getting onto an interplanetary trajectory at 11.5 km/s requires 3.7 km/s dV from LEO at 7.8 km/s, unassisted. The tug could get it to 10.9 km/s and subsequently be recover itself from an ellipse apogeeing near the moon's orbit. The interplanetary craft dV from that tug assist point is only 0.6 km/s! Tug-assisted departure makes a big difference!
I think Starship might actually have its flap burn-through problem solved, and its heat shield pretty much determined, and also have demonstrated propellant transfer from 1 vehicle to another, in about a year, which is very near-term. That means a tug modification could be flying not that long afterward. And the mass capacity it could fling onto hyperbolic departure is astonishing: just short of 500 metric tons or thereabouts. Arrivals, not so much: nearer only 175 tons.
The real long pole in the tent is not modifying Starship or some other upper stage to be used as a space tug, it is having a good facility in LEO to assemble interplanetary payloads and then dock tugs to them, using remote-operated mechanical arms, plus a ready means and depot from which to refuel the tugs and fuel the interplanetary craft.
That won't happen on a 2-year timescale! If Gateway gets built at the moon, the assembly and propellant depot facility in LEO will never get built. There is not enough $ to do both.
But with a tug assisting departures and maybe arrivals, why would we need Gateway? THAT is the really telling question no one is asking.
GW
Does your proposal require multiple orbital refuelings?
Robert Clark