Exoscientist
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Posts posted by Exoscientist
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11 hours ago, sevenperforce said:
The Cygnus itself has a mass of 3,300 kg, which could maybe be reduced to 2,630 kg if you do a complete redesign and strip away everything that makes it useful.
The original size Cygnus has volume 18 cu. meters, nearly the size of the Orion capsule itself, and only weighed 2,000 kg. Since it would only be needed for a two crew for a week, you would not need the larger size versions.
12 hours ago, sevenperforce said:With an added 0.6 tonnes ESM dry mass as proposed by @RCgothic, Orion needs ~6 tonnes of remaining props to develop the 900 m/s of dV needed to return from LLO to Earth entry interface post-mission. The launch mass of the entire Apollo LM (initial pre-extension configuration, Apollo 11-14) was 15.2 tonnes. Unfortunately, Orion can't brake that much weight from TLI into low lunar orbit, not even with @RCgothic's upgrade. It would need to be carrying a minimum of 13.4 tonnes of propellant plus the 6 tonnes it needs for the return.
The Orion service module already has 9 tons propellant, plus adding on an 10 additional tons brings the propellant load to 19 tons.
Robert Clark
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A Moore’s Law for space
Edward Lu January 29, 2024
Something fundamental has changed in space. After decades of slow growth, the number of spacecraft launched annually has doubled every two years since 2015. And the trend shows no sign of slowing, with tens of thousands of planned spacecraft to be launched over the next few years. This exponential growth is reminiscent of Moore’s Law, the decades-long observation that the number of transistors on integrated circuits doubles every two years. The consequences of the continuation of Moore’s law and the ever-increasing computing power for lower costs over the past six decades has changed the course of our society, our economy, and our way of life. Could we be witnessing a similar revolution in space?
https://spacenews.com/moores-law-space/
This is great news for advancing reusability in space launchers. With reusability and large numbers of launches prices will drop
Robert Clark
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The need for such large number of launchers will spur the development of reusability in European space as well. In response to a question about how long to build a new Delta IV, ULA head Tory Bruno responded two years. A reusable launcher that can be launched again within a matter of weeks would have a major advantage.
I wrote the following blog post in regards to advancing European manned spaceflight. However, in regards to a financial motive, a greater reason for developing the launchers I discuss is advancing reusability in European spaceflight:
Towards Every European Country's Own Crewed Spaceflight, Page 2: saved costs and time using already developed, operational engines.
https://exoscientist.blogspot.com/2024/01/towards-every-european-countrys-own.htmlKey, and most controversial, points:
1.)Any European country can field their own, independent, manned flight capable launcher in under 2 years, IF they design it around already developed and operational engines.
2.)By eliminating the two SRB’s on the Ariane 6, and instead adding 1 or 2 additional Vulcain engines on the core stage, ArianeSpace can field such a launcher in less than a year.
3.)In any case, such a manned flight capable launcher by following the commercial space approach spear-headed by SpaceX could be developed for less than $200 million, assuming they didn’t have to pay engine development costs by using already operational engines.
Robert Clark
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Space wars: Europe’s master plan to counter Elon Musk’s Starlink
The Starlink satellite system is crucial for the Ukrainian military, but there are problems.
The European Union aims to sign contracts worth billions by the end of March to build and operate a new constellation of communication satellites | Mariana Suarez/AFP via Getty Images
JANUARY 25, 2024 5:09 PM CET
BY JOSHUA POSANER
https://www.politico.eu/article/space-wars-europe-masterplan-counter-elon-musk-starlink/This is great news. An argument against Europe producing a reusable launcher to compete with SpaceX is the lack of a European market for it. A European satellite system to compete with Starlink requiring thousands of satellites would provide a definite market for large numbers of launches that would be done most cheaply by reusable launchers.
This article about the IRIS2 systems says it will only use hundreds of satellites. But both the Starlink and Project Kuiper systems will use thousands of satellites. And the Chinese systems intended to be competitive to the American systems will also use thousands of satellites. It is unlikely this system can be competitive to these systems without also using thousands of satellites.
Robert Clark
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11 hours ago, sevenperforce said:
There is no uncertainty here at all. The proposed Exploration Augmentation Module (which is based on the proposed four-segment "Super" version of the Enhanced Cygnus in your post, not the much lighter Standard Cygnus) could support a crew of four for up to 60 days while berthed to Orion. It cannot do so independently, and there was no suggestion or implication by anyone that it could do so independently.
On 1/28/2024 at 8:50 AM, Exoscientist said:The uncertainty stems from the phrasing in this passage in this article, which after all, is not a technical paper:
ORBITAL PROPOSES FUTURE DEEP SPACE APPLICATIONS FOR CYGNUS.
SPACEFLIGHT INSIDER
MAY 1ST, 2014
Orbital’s proposal, outlined in this PDF, involves docking a Cygnus spacecraft with Orion to serve as a habitation and logistics module on longer flights. For these missions, the re-purposed Cygnus would be called the Exploration Augmentation Module (EAM). With its current life support systems used to transport pressurized cargo and experiments to the ISS, Cygnus is stated as being already suitable for the long term support of a crew. While berthed to Orion, Cygnus could support a crew of four for up to 60 days. Cygnus also has the capability of storing food, water, oxygen, and waste and features its own power and propulsion systems. The EAM would utilize the enhanced configuration Cygnus, which will begin flying larger cargoes to the ISS beginning with CRS-4 in 2015. An even larger version is also being proposed, featuring a 4-segment pressurized cargo module.
https://web.archive.org/web/20160512141500/https://www.spaceflightinsider.com/missions/commercial/orbital-proposes-future-deep-space-applications-cygnus/ (I couldn’t get that Spaceflightinsider.com link to open, so I’m giving the Archive.org link here.)
The first part of the passage suggests the Cygnus already has life support systems in its role as a cargo supply craft for the ISS. But then the second part of the passage suggests it would need to be connected to the Orion to support a crew of 4 for 60 days.
IF the Cygnus already has life support it’s possible this alone would support a crew of, say, two, for a period of, say, a week.
Robert Clark
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16 hours ago, RCgothic said:
There seems to be a discrepancy in some of the DV maps I've been using. Depending on whether it's 680m/s or ~820m/s - if the latter I get about 10.7t additional mass required to get to LLO with a 15t payload and return with ~100m/s margin for free-flight and rendezvous. So that's 60t to TLI required, as near as matters, to land an Apollo LM on the moon using SLS and Orion.
The fueled Orion/service module weighed about 26.5 tons:
Specifications Spacecraft type Crewed Launch mass - CM: 22,900 lb (10,400 kg)
- ESM: 34,085 lb (15,461 kg)
- Combined mass: 58,467 lb (26,520 kg)
- Total with LAS: 73,735 lb (33,446 kg)
Dry mass - CM: 20,500 lb (9,300 kg) landing weight
- ESM: 13,635 lb (6,185 kg)
https://en.m.wikipedia.org/wiki/Orion_(spacecraft)
Then with 10.7 tons extra propellant and tankage and a 15 ton lunar lander the total mass needing to get to TLI is:26.5 + 10.7 + 15 = 52.2 tons .
Perhaps the higher 60 ton you’re getting comes from including the Launch Abort System(LAS)? But that is jettisoned well before reaching orbit .
Robert Clark
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4 hours ago, SunlitZelkova said:
Starship HLS already has a prototype flying in the form of the current ships, and has already appeared in metal in the form of mockups. Even the tanker variants have been manufactured in some form, IIRC. How is this new lander going to get ahead of something that already exists?
Not exploding is an important requirement for a rocket, especially for one intended to carry crew.For the alternative proposal using a hydrolox stage for the propulsion of a lunar lander, this propulsive stage already exists and been flown multiple times for the upper stage of the Ariane 4 rocket.
For the Cygnus capsule, it has been flown multiple times as a unmanned cargo craft and is planned to be a manned component of a space station. As I mentioned though I’m not certain it has it’s own independent life support systems. The Cygnus itself weighs 2, 000 kg. I don’t think adding life-support would add too much more to that mass.
Robert Clark
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17 hours ago, RCgothic said:
I do agree a larger service module on Orion would be better, given where we've ended up. It would actually improve SLS Block 2's co-manifest payload to NRHO as well, as SLS B2 can throw more combined mass of Orion/ESM and payload to NRHO than Orion can actually brake into that orbit and still return.
SLS might *possibly* be able to do a single stack Apollo style mission with an Apollo LM *if* the ESM is upgraded with an additional 6.5t of propellant and 0.6t dry mass. The total mass to TLI would then be ~ 55t including the payload adaptor and intermediate fairing. Block 2's stated capabilities are 49t to TLI, so on paper it's a no-go although they might be sandbagging a bit.
But I don't know why we'd want to.
Which is what we keep coming back to in this discussion. Apollo style with SLS gets ~3days on the surface every other year and a few hundred kg of samples each time at most, after a multi-year delay to develop a lander that small. Artemis HLS style gets potentially months on the surface per crew launch and tonnes of sample return, with scope to bypass SLS entirely and go multiple times a year and an architecture that also works for Mars, with landers that have already cut metal.
I just don't understand why anyone would prefer Apollo-style.
Your estimated extra propellant of 6.5 tons required might not be including the required propellant to also get the Orion back to Earth. I estimated 10 tons extra propellant required.
But anyway, this latest blog post was to keep the current size service module, still stage from NRHO not low lunar orbit, but use a hydrolox lander to deal with the larger delta-v needed for staging from NRHO. The proposal would still be heavier to TLI than before though. The Orion/service module weighs 26.5 tons. A 15 ton lander would bring the TLI mass to 41.5 tons. I made two suggestions to deal with this added mass to TLI: adding a Centaur V at 50-ton size as a 3rd stage or going back to the J-2X engine for the Boeing EUS upper stage that had been planned. A preliminary calculation suggest they should be able to do > 42 tons to TLI.
A ca. 2 ton mass lunar crew module should be able to do over a week stay on the Moon based on the Cygnus module. The uncertainty is in whether the usage described in the article below includes independent life-support on the Cygnus or if it is taking life-support from the Orion:
ORBITAL PROPOSES FUTURE DEEP SPACE APPLICATIONS FOR CYGNUS.
SPACEFLIGHT INSIDER
MAY 1ST, 2014
Orbital’s proposal, outlined in this PDF, involves docking a Cygnus spacecraft with Orion to serve as a habitation and logistics module on longer flights. For these missions, the re-purposed Cygnus would be called the Exploration Augmentation Module (EAM). With its current life support systems used to transport pressurized cargo and experiments to the ISS, Cygnus is stated as being already suitable for the long term support of a crew. While berthed to Orion, Cygnus could support a crew of four for up to 60 days. Cygnus also has the capability of storing food, water, oxygen, and waste and features its own power and propulsion systems. The EAM would utilize the enhanced configuration Cygnus, which will begin flying larger cargoes to the ISS beginning with CRS-4 in 2015. An even larger version is also being proposed, featuring a 4-segment pressurized cargo module.
As to why this approach, the Starship HLS is still uncertain for an Artemis III or Artemis IV timeline. Even if SpaceX succeeds at flights to LEO, they still need to demonstrate reusability and orbital cryogenic refueling.
This approach still allows sustained lunar presence because it would not use SLS for cargo and habitat delivery. That would use far cheaper commercial launchers instead.
Bob Clark
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On 9/29/2023 at 8:28 PM, Exoscientist said:
Nevertheless, it is possible to do a single launch of the SLS with a light-weight Apollo-sized lander with all the components of Orion capsule/Service Module/lunar lander all carried on that one single SLS launch.
The NRHO was chosen because it has a lower delta-v requirement to get there than going to low lunar orbit. Here’s the delta-v requirements:
This earlier post expanded out:Possibilities for a single launch architecture of the Artemis missions, Page 4: lightweight landers from NRHO to the lunar surface.
https://exoscientist.blogspot.com/2024/01/possibilities-for-single-launch.htmlA major flaw in the design of the SLS was that the Orion capsule was saddled with a too small service module:
Rather than giving Orion a larger service module than Apollo’s due to its twice larger size, it was instead given one 1/3rd smaller. Why? It stems from the earlier, now cancelled Constellation program. Constellation was to have rocket the Ares 1 to carry astronauts to LEO in the Orion capsule, and a larger launcher the Ares V to carry the other lunar mission elements to rendezvous with the Orion in LEO for the flight to the Moon.
However, the Ares I was powered by a single SRB as the first stage and that did not have enough power to get a large service module and the Orion to LEO. Then the service module was cut down in size.
But when Constellation was cancelled it was decided to keep the Orion, and with that its service module also. But now the decision to use a smaller service module made no sense. The Ares I was cancelled so it made no sense to use limitations on the size of the service module coming from a rocket that wouldn’t be used.
But government programs have inertia. It’s hard to change programs already decided on. It becomes like they are fixed in stone. Since the Orion capsule is kept, its service module is kept as well.
It would be a relatively easy fix, both technically and financially, to increase the size of the service module propellant tanks so that the service module could carry the Orion and an Apollo-sized lunar lander to low lunar orbit with enough propellant left over to carry the Orion back to Earth again.
The only problem is convincing NASA to do it. It’s because of that too small service module that NASA had to come up with other destinations at the Moon that the Orion could reach and come back from. Thus was selected the NRHO orbit(near rectilinear halo orbit).
Since the NRHO is decided upon, could we get a lunar lander that could be used on the SLS to get a single launch lunar landing architecture that staged from NRHO? The answer is yes. If we made it an Apollo-sized lander but hydrolox powered instead of using storable propellant engines.
The hydrolox lunar lander would need low-boiloff tech. But ULA has done a lot of research on this in regards to their ACES(Advanced Cryogenic Evolved Stage) so the tech likely could be used in the near term for a lunar lander.
Bob Clark
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Congress becoming concerned with the frequent delays of the Artemis program, that China may beat us back to the Moon:
US must beat China back to the moon, Congress tells NASA.
By Mike Wall published 3 days ago
'It's no secret that China has a goal to surpass the United States by 2045 as global leaders in space. We can't allow this to happen.'
https://www.space.com/us-win-moon-race-china-congress-artemis-hearingBob Clark
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Team Reveals Remaining Asteroid Sample
Johnson Space Center Office of Communications
JAN 19, 2024
A top-down view of the OSIRIS-REx Touch-and-Go-Sample-Acquisition-Mechanism (TAGSAM) head with the lid removed, revealing the remainder of the asteroid sample inside.
Photo: NASA/Erika Blumenfeld & Joseph Aebersold
https://www.nasa.gov/image-article/nasas-osiris-rex-curation-team-reveals-remaining-asteroid-sample/
Bob Clark -
5 hours ago, Nuke said:
i wonder if elon would let me borrow a raptor for snow removal.
You could always use his NotAFlamethrowerTM
Robert Clark
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1 hour ago, darthgently said:
Not sure if included in Musk's update above, but I'll leave this here
Odd they didn’t just partially fill the tanks.
Bob Clark
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Toby Li @tobyliiiiiiiiii
Jan 6
Elon Musk to provide 2024 Starship Update on January 11. Confirmed on an X livestream,@elonmusk announced he will conduct a SpaceX company talk including a Starship update next Thursday. I'm hoping to hear details regarding Starship IFT-2's post-flight analysis, plans for IFT-3 & beyond, and updates on Starship HLS milestones.
https://twitter.com/tobyliiiiiiiiii/status/1743529920322846812This is supposed to be an internal speech to SpaceX employees, but in the past was released to the public.
Robert Clark
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On 1/9/2024 at 2:33 PM, Shpaget said:
The very bottom of the forums.
It's quite fugly and looks unfinished, but at least it's dark.
Thanks for that. I can tell now when I am copying something from another forum with different formatting when it becomes unreadable on this forum when reading in dark mode.
By the way, I just realized that Elon tweet I copied from twitter where he says the expendable Starship might have a dry mass of only 40 tons, has that same problem. But you can read the tweet by clicking the link to the twitter post.
Bob Clark
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13 hours ago, NFUN said:
I can just barely read it without needing to out my phone in my face
How does this look?
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I have been accused of being anti-SpaceX because of my criticism of the Starship. Actually, after a calculation I'm convinced the Starship can be operational, like, tomorrow, with relatively small design changes:
Towards advancing the SpaceX Starship to operational flight: SpaceX should lower the Raptor chamber pressure and thrust level.
https://exoscientist.blogspot.com/2024/01/towards-advancing-spacex-starship-to.html…
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I applied the option the forum offers of inserting text in plain-text format.
Robert Clark
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On 1/8/2024 at 5:53 PM, tater said:
Whatever you did starting there, the font changes and it's practically unreadable in dark mode (an my forum is always on dark mode). There are a few of your posts where you do this. Do you intentionally change font/color, or is it a non-plain text quote or something?
I'm not changing my forum theme to read the post (can see it in your quote), but is that the booster, or the ship? In the case of the ship—doesn't work on Mars. Off the table. For the booster, you are of course exactly right.
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I frequently copy and paste from other forums which may introduce new fonts this forum is not familiar with. When putting them together I frequently use the “Note” app on the Apple iPad. That might introduce other fonts. Here’s an experiment: I’ll try using the “Pages” app on the iPad instead which allows you to select the font.
So here’s the previous post you couldn’t read in “dark mode” but copied into “Pages” and put in Arial font then recopied onto this forum:
_____________________________________________________________________________________________________
I have been accused of being anti-SpaceX because of my criticism of the Starship. Actually, after a calculation I'm convinced the Starship can be operational, like, tomorrow, with relatively small design changes:
Towards advancing the SpaceX Starship to operational flight: SpaceX should lower the Raptor chamber pressure and thrust level.
https://exoscientist.blogspot.com/2024/01/towards-advancing-spacex-starship-to.htmlThe Raptor engine has shown continued failures on all of test stands, Starship low altitude landing test flights, and the two orbital test flights. But the Raptors on the booster on the last test flight were able to complete the ascent part of the flight without failures. They failed only after the attempted to relight.
Multiple-lines of evidence suggest that on that last test flight SpaceX throttled down the Raptors on the booster to less than 75% while those on the Starship were run at ~90%. I've suggested this is why the booster engines were able to fire reliably during the ascent and those on the upper stage were not.
If this is the case, then it suggests a method to get Raptor reliability: run them at ~75% throttle on both stages. But if keeping the same stage dry masses this would result in the payload of the reusable version being reduced to approximately in the range of 100 tons from 150 tons.
Instead, I advise first start with reducing the dry masses by optimally lightweighting the expendable versions of both stages. Surprisingly this gives a greater expendable payload than the expendable payload of the current version. Secondly, I suggest using winged, horizontal approach to reusability gives a much reduced payload loss due to reusability. Thirdly, basic orbital mechanics shows high delta-v missions such as to the Moon or Mars are done more efficiently by using more stages. Then a third stage is suggested for the Superheavy/Starship, a mini-Starship as it is called by Robert Zubrin.
This allows single launch and fully reusable missions to the Moon or Mars. No refueling flights required.
_____________________________________________________________________________________________________
Let me know if this is legible. By the way, about your question I wanted to do the optimal lightweighting for both the Starship and SuperHeavy as expendables. The savings in weight would be more extreme in the case of the Starship though.
My entire argument is based on this one Elon tweet:
Probably no fairing either & just 3 Raptor Vacuum engines. Mass ratio of ~30 (1200 tons full, 40 tons empty) with Isp of 380. Then drop a few dozen modified Starlink satellites from empty engine bays with ~1600 Isp, MR 2. Spread out, see what’s there. Not impossible.The difference of 80 tons between this Elon estimated dry mass of 40 tons for the expendable Starship and the current reusable dry mass of 120 tons is *huge*, especially for an upper stage where the difference subtracts directly from the payload mass.
Robert Clark
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On 1/4/2024 at 4:32 PM, sevenperforce said:
No one wants a sortie lander. To achieve the goals of Artemis, we need substantial downmass -- something closer to the 46 tonne (launch) mass of the Altair lander. Add a reasonably-sized crew capsule, and doing this in a single launch means a vehicle capable of throwing upwards of 70 tonnes to TLI.
I’m responding to this comment from the Starship discussion here since my response is more general in nature on lunar missions.
I don’t agree you need rockets giving 70 tons to TLI to get sustainable architecture allowing manned lunar surface stations, a la how the ISS is in low Earth orbit. As I mentioned before the SLS is too expensive, upwards of $4 billion per flight, to be used for cargo only missions. Better to use far cheaper commercial flights for that purpose.
Robert Zubrin gave a plan for producing a Moon base using three launches of Falcon Heavy plus a launch of the Falcon 9 to carry the crew to LEO:
Op-ed | Moon Direct: How to build a moonbase in four years
Robert Zubrin March 30, 2018
https://spacenews.com/op-ed-moon-direct-how-to-build-a-moonbase-in-four-years/
Key for his plan is using a “Lunar Excursion Vehicle” (LEV) of ca. 12 ton gross mass that is hydrolox powered as a lunar lander. This would require near zero-boiloff tech, but Zubrin thinks this is doable with current tech.
For the two cargo missions launched by Falcon Heavy, Zubrin would use a larger hydrolox stage for the lander at ca. 40 ton size, a bit smaller than Centaur V, that could deliver ca. 12 tons of cargo to the lunar surface.
Quite notable about his plan is as far as the manned flights it would require a single Falcon Heavy rocket as the launcher to get the hydrolox in-space stages to LEO. The FH has a payload capacity of 63 tons to LEO. So an only 63 ton launcher could get the required in-space stages to LEO, which could then do a manned round trip flight to the lunar surface. This small size for the launcher is coming from the fact the in-space stages are so much lighter being powered by hydrolox.
The Falcon Heavy however is not manrated though. So it would need a separate man-rated launcher to get the astronauts to LEO. This man-rated launcher could be the Falcon 9 but it doesn’t have to be.
Robert Clark
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I have been accused of being anti-SpaceX because of my criticism of the Starship. Actually, after a calculation I'm convinced the Starship can be operational, like, tomorrow, with relatively small design changes:
Towards advancing the SpaceX Starship to operational flight: SpaceX should lower the Raptor chamber pressure and thrust level.
https://exoscientist.blogspot.com/2024/01/towards-advancing-spacex-starship-to.htmlThe Raptor engine has shown continued failures on all of test stands, Starship low altitude landing test flights, and the two orbital test flights. But the Raptors on the booster on the last test flight were able to complete the ascent part of the flight without failures. They failed only after the attempted to relight.
Multiple-lines of evidence suggest that on that last test flight SpaceX throttled down the Raptors on the booster to less than 75% while those on the Starship were run at ~90%. I've suggested this is why the booster engines were able to fire reliably during the ascent and those on the upper stage were not.
If this is the case, then it suggests a method to get Raptor reliability: run them at ~75% throttle on both stages. But if keeping the same stage dry masses this would result in the payload of the reusable version being reduced to approximately in the range of 100 tons from 150 tons.
Instead, I advise first start with reducing the dry masses by optimally lightweighting the expendable versions of both stages. Surprisingly this gives a greater expendable payload than the expendable payload of the current version. Secondly, I suggest using winged, horizontal approach to reusability gives a much reduced payload loss due to reusability. Thirdly, basic orbital mechanics shows high delta-v missions such as to the Moon or Mars are done more efficiently by using more stages. Then a third stage is suggested for the Superheavy/Starship, a mini-Starship as it is called by Robert Zubrin.
This allows single launch and fully reusable missions to the Moon or Mars. No refueling flights required.
Robert Clark
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1 hour ago, zolotiyeruki said:
You still haven't answered the question: What benefit would static fires bring over test flights?
"Because that's how it has always been done" is not an argument. It's a logical fallacy called "Appeal to tradition." Tradition can result from rational thinking and sound logic, but is not proof of such.
"Suggests this is not a better approach" - Hang on. About the only similarities between the programs are that they both involve big rockets and have suffered some failures.* Literally nothing else is common between them. Different countries, gov't vs private, a half-century of technological advancement, different goals, different politics. You're trying to compare apples to oranges here.
On the static stand you can gradually build up to full thrust and full flight duration. If you see out of nominal state for one or more engines, you can shut the test down, examine the engines not operating properly and compare to the ones that are. Then try again gradually building up to full flight conditions. In contrast if one or more engines fail in flight, even if it didn’t explode but had to be shutdown, usually you have to destroy it by FTS for fear it will stray too far out of the safety zone.
Robert Clark
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1 hour ago, zolotiyeruki said:
A few counterpoints:
1) You have written many, many words, but you still haven't answered the simple question: "what benefit would ground testing give you that modern flight testing doesn't?"
2) Sure, SpaceX and NASA have done integrated tests in the past. That doesn't mean they absolutely must adhere to that same practice for every engine and every vehicle. A wise young guy once told me "tradition has to claim on sanctity." Just because a full-up, full-thrust, full-duration static test was called for under a previous program a decade or a freaking half century ago doesn't mean that the same test is appropriate for this program at this stage with SpaceX's current development philosophy.
Consider, that is the standard industry practice. It is not just SpaceX and Nasa doing in that way in the past. Every company in the industry does it that way. Every company could just test single engines on test stands if they wanted to. That would be much cheaper. Instead they follow the accepted practice of doing full flight analog testing prior to test flights.
That the Soviet N-1 experienced not just engine shutdowns but engine explosions on every test flight and the SuperHeavy/Starship also experienced the same thing, including the engine explosions, suggests this is not a better approach to getting reliable engines.
Robert Clark
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18 hours ago, sevenperforce said:
Dude, this is hogwash. You have absolutely no idea what the planned burn time was for any of these tests, what was being tested, whether these were acceptance tests or tests to failure or outlier tests...nothing.
You're looking for patterns that don't exist. You might as well throw in your lot with the day-trading dopes arguing about which candles predict a new stock market trend.
You don’t have to take the video authors word on this. You can judge for yourself if there is a most common length over which most of the tests are done:
Robert Clark
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8 hours ago, zolotiyeruki said:
This is the question that Exoscientist has been studiously avoiding. If, like SpaceX, you have the ability to flight test the hardware, why would you limit yourself to ground testing? I'm trying to think of what advantages a ground test fire would have over a flight test, and I'm coming up empty-handed.
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I have discussed this. It is standard industry procedure to do full thrust, full up(all engines), full flight duration(actual mission length) static fire tests before doing flight tests. Even SpaceX did this when qualifying the Merlins on the Falcon 9 for flight:
SpaceX Testing - Falcon 9 Engine Test
147,136 views Nov 25, 2008
The full mission duration test firing of the Falcon 9 first stage lasting nearly 3 minutes. The nine Merlin engines produced 855,000 lbs. of thrust and consumed over half a million pounds of liquid oxygen and rocket grade kerosene during the test.And this video shows this being done for the Saturn V first stage:
Saturn V S IC Static Firing (archival film)
34,163 views Aug 15, 2018
This film provides an overview of testing of the Saturn V first stage, the S-IC stage at NASA's Marshall Space Flight Center during the Apollo Program. The five F-1 engines which made up the stage generated a combined seven and a half million pounds of thrust.Such tests are more challenging for the engines and the stages. But that is the point.
It is because such tests were done that the Falcon 9 and the Saturn V were spectacular successes.
Bob Clark
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On 1/3/2024 at 3:17 PM, Exoscientist said:
This video attempts to argue the Raptor is reliable by looking at static fire tests.
A key question in the video is how many of the test fires fall short of the expected length, suggesting a test failure or for whatever reason the engine had to be shutdown. The video host suggests it is small number. I suggest it is more than it should be for an engine at this stage in its development. Someone may want to count the percentage
themselves where it is displayed graphically at about the 5:55 point in the video.Also I don’t like the lengths of the engine tests. The video host says most are about 2 minutes, 120 seconds, suggesting that is where SpaceX thinks that is what the flight burning time should be. But judging from the test flights for the booster that should be in the 2 minutes 40+ seconds range, 160+ seconds, which means even for static fires of individual engines SpaceX is not doing realistic static fires:
Planned mission timeline[34]
….
00:00:55 Max q (moment of peak mechanical stress on the rocket — Later and lower Max q than planned[42]
00:02:49 Main engine cutoff (MECO) — Not attempted[43]
00:02:52 Stage separation
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https://en.m.wikipedia.org/wiki/SpaceX_Starship_integrated_flight_test_1#Flight_profile.Additionally, SpaceX needs to be open about how many of these static fires are done at full power.
The video argues the Raptor has high reliability based on the tests on static stands at McGregor.
The author says the reliability is high because “most” tests were able to reach a planned length of 115 to 120 seconds. The problem is for a rocket engine to be used to power a crewed vehicle you want very high reliability. For instance the SLS has estimated reliability for its components of 99.9% and for the Merlins based on the number of successful flights we can estimate it as better than 99.9%. That is, less than 1 in a thousand would be expected to fail.
But going by counting the number of tests for the Raptor that fail to reach that 115 to 120 second mark, it may be 1 in 5 to 1 in 6 fail to reach it. Note as the author of the video observes some tests are planned to be shorter. For some for instance they were intended to be about 47 seconds long. But there are a block of tests I marked off in the attached image that appear to be aiming for that 115 to 120 second mark, and several of them don’t make it. I estimate 5 or 6 out of the 30 I marked off failed to reach that planned burn length.
Another questionable issue of these static tests is the planned lengths. The largest portion them were of a planned length of about 120 seconds, 2 minutes. But judging by the two test flights the actual burn time for the booster is in the range of 2 minutes 39 seconds to 2 minutes 49 seconds range. Only very few of the test stand burns went this long or longer.
The video gives a link where you can watch the test stand burns NSF.live/McGregor. Another useful aspect here is you may be able to judge the power level of the burns. There is a graphic that shows the sound level of the burns. From that you may be able to judge whether or not the engines were firing at or close to full thrust.
In the image below, the burns in white are those shorter burns of about 47 second lengths the author of the video made note of. They may be tests of the boost back or landing burns. The ones I’m commenting on are under the yellow bar, which I estimate to be at about the120 burn time. There 5 or 6 out of 30 don’t reach the planned burned time.
 Robert Clark
Artemis Discussion Thread
in Science & Spaceflight
Posted
Right. That is cargo mass. But other references put the dry mass of the Cygnus cargo spacecraft even in the "Enhanced" version as under 2,000 kg:
Cygnus consists of a Pressurized Cargo Module that is built by Thales Alenia Space of Italy and a Service Module built by Orbital, based on Orbital’s GEOStar Satellite Bus and Dawn spacecraft elements to reduce cost and risk.
Cygnus is booked for a single COTS Demo mission to ISS and a total of eight CRS flights. For its first four flights, Cygnus flies in its standard configuration. When the Antares is upgraded with the Castor 30 XL second stage, Cygnus will transition to its enhanced version to carry more cargo to ISS. Cygnus standard carries 2,000kg of cargo to ISS while the enhanced version has a cargo capability of 3,500kg, limited by launch vehicle performance.
https://spaceflight101.com/spacecraft/cygnus/
(Note: to maintain the format of the table, this copies directly from the web page so the numbers might not be visible in "dark mode".)
For the use as a lunar crew module, the Cygnus' service module that provides its propulsion won't be used since the propulsion will be provided by a separate, existing rocket stage.
Bob Clark