Article in Nature does not find Mars Starship missions feasible.

RGClark · 2024-08-02 05:45:37

About feasibility of SpaceX's human exploration Mars mission scenario with Starship.
Scientific Reports
volume 14, Article number: 11804 (2024)
https://www.nature.com/articles/s41598-024-54012-0

Bob Clark

tahanson43206 · 2024-08-02 06:55:29

This post is reserved for an index to posts that may be contributed by NewMars members over time.

As a note about this topic (before reading the article) NewMars Senior Moderator RobertDyck has been working on a proposal for a large space ship suitable for safe transport of up to and perhaps even over 1000 passengers. The principle at work is artificial gravity via rotation.

The Large Ship topic is quite lengthy.

(th)

tahanson43206 · 2024-08-02 07:11:57

This post follows a first scan of this long paper.

The paper appears (to me at least) to have potential to stand up to the close scrutiny that members of this forum will provide.

Here are the authors:

Author information
Authors and Affiliations
German Aerospace Center (DLR), Institute of Space Systems, Bremen, Germany
Volker Maiwald
Faculty of Production Engineering, University of Bremen, Bremen, Germany
Mika Bauerfeind
Chair of Space Systems, Technical University Dresden, Dresden, Germany
Svenja Fälker & Christian Bach
Technical University Braunschweig, Braunschweig, Germany
Bjarne Westphal

There are 72 references.

There is plenty of math to satisfy our most discriminating members.

One detail that caught my eye is the need for a elevator to unload Starships on Mars. This might have some of the attributes of the towers built by SpaceX in Texas to lift Starship onto Super Heavy.

Robots could build such a structure on Mars ahead of the first human landing.

(th)

GW Johnson · 2024-08-02 08:12:59

I've downloaded the pdf of the report. Will have to look closely at it. Thanks.

GW

kbd512 · 2024-08-02 15:44:17

Which version of Starship did they analyze?

From reading their report, it looks like the initial version. SpaceX and Elon Musk have already stated that this current version isn't the one going to Mars.

index.php?action=dlattach;topic=60676.0;attach=2275656;image

I think Starship 3 has the payload performance these guys assert it needs to have for Mars missions.

Edit:
Assuming a dry / payload mass of 250t, a propellant load of 2,300t, and 382s Isp, I get 8,700m/s of ΔV. If we knock 5% of that off for maneuvering / losses / 2% residuals, then 8,265m/s. That is well in excess of what appears in that analysis document.

Last edited by kbd512 (2024-08-02 15:51:02)

GW Johnson · 2024-08-03 09:34:15

Just bear in mind that these are projections for designs not yet built and tested. Not even Starship-1 has met the pre-build predictions for it. Things ALWAYS turn out different than expected in flight test. That is EXACTLY why we flight test.

GW

kbd512 · 2024-08-03 13:04:41

I think SpaceX should've started with 10m diameter cores like the Saturn V and stuck with LOX/RP-1, at least for the booster. This combination has so much flight heritage for a reason. Now that we have much more efficient CFD program-optimized turbopump impeller designs and we can make kerosene burn almost as clean as natural gas does, there's little reason to use a propellant combination with 20% less density and total impulse per unit volume for the booster. The upper stage benefits greatly from improved Isp because it's much smaller / lighter and already moving downrange at high speed when it lights its engines.

Starship 3's booster will contain 4,551m^3 of LOX/LCH4, at 890kg/m^3.
At 348s (90% of Vacuum Isp), Itotal = 13,534MNs
4,551m^3 of LOX/RP1 is 5,115,324kg, at 1,124kg/m^3.
At 338s (90% of Vacuum Isp), Itotal = 17,094MNs (if thrust and mass flow remained the same, but thrust and mass flow would increase)

That's a 20% booster performance increase right there, even if RP1 thrust doesn't improve at all over LCH4, but it will improve. Coking must not be that much of an issue since they're reusing Falcon boosters all the time. LOX/LCH4 Raptors can still be part of the upper stage if it makes the propellant so much easier to synthesize on Mars, but I doubt it's that much easier to make and store than kerosene since we already synthesize kerosene here on Earth at an industrial scale for the airline industry.

RobertDyck · 2024-08-03 21:16:36

I have said before and will repeat: a far more practical approach would be Mars Direct using Starship as the launch vehicle. It's large enough to deliver a hab into LEO with a fully fuelled TMI stage, and Starship will still be recoverable. Two launches: ERV and hab.

I came up with a modified architecture in 2002, with later updates. My idea is a Mars Ascent Vehicle (MAV) sent first, then the manned assembly. I could waste time how to do it with other launchers, but this would require one Starship for the MAV, and two for the assembly. The assembly would include two habits: one for surface, the other would remain in Mars orbit and used for return. The Interplanetary Transit Vehicle (ITV) is the second have, optimized for space. The ITV would aerocapture into Earth orbit and be reused. The MAV would be the TEI stage, and would be the counterweight for rotation just like the Earth-to-Mars leg. Include a Dragon capsule for Earth atmospheric entry.

Either way, start with science missions. But rather than each mission to a different site, we've done enough unmanned rovers already to narrow down base location. Multiple missions to one site build up infrastructure.

Then build a permanent base for 12 crew using insitu materials and these science habs. If each hab carries 6 astronauts instead of just 4, that only requires 2 habs. I visualize a base like Mars Homestead project.

Then use the 12 crew base to build a larger base for 100 people. When the first passenger Starship arrives with 100 settlers, their accommodation and life support is waiting for them.

GW Johnson · 2024-08-04 10:02:58

That's a good plan, except for one thing: there are no feasible Mars Ascent Vehicle designs floating around as yet. These things have to be sent there fully fueled (somehow), landed, and still be viable on the surface for up to years at a time. NOBODY really has such a thing.

GW

RobertDyck · 2024-08-04 11:46:35

GW Johnson,
No they don't. ISPP is a basic fundamental of Mars Direct. The Earth Return Vehicle (ERV) from Mars Direct or Mars Ascent Vehicle (MAV) from NASA's Design Reference Mission both use ISPP. They land with propellant tanks practically empty, just a little hydrogen. Mars at night temperature is almost cold enough to freeze CO2 into dry ice, so a freezer drops the last few degrees to accumulate dry ice. The freezer coils are in a container that's open at night but sealed at dawn. Then the heat pump reverses, heating the dry ice to sublimate it. That pressurizes the container with almost pure CO2 gas, just a trace of the other gasses of Mars atmosphere. Hydrogen and CO2 are run over a hit catalyst, converting to methane and water. This is called a Sabatier reactor, invented by Paul Sabatier and used to produce methane for gas lights in the first decade of the 1900s (20th century). Methane is liquefied by a freezer, stored in a fuel tank. Water is run through an electrolysis tank, split into hydrogen and oxygen. The oxygen is also liquefied by a freezer, stored in an oxidizer tank. Hydrogen is recycled. Each tonne of hydrogen becomes 18 tonnes of LCH4/LOX propellant. Since equipment includes liquefaction equipment, any boil-off is retained and re-liquified. The whole thing is powered by a small nuclear reactor. The US military developed a small reactor for space in the 1980s, completed in 1992. An updated design was developed later, completed in 2007.

Mars Direct was developed in the last quarter of 1989 and first half of 1990. First presented to NASA in June 1990. It was developed by Dr Robert Zubrin and his partner David Baker. Dr Zubin got a contract from NASA to develop brass-board prototypes of ISPP.

To ensure LCH4 and LOX have the right ratio for the rocket engine, a little more LOX is required. This would be produced by direct CO2 electrolysis, converting 80% of CO2 into CO (carbon monoxide). Since CO is a natural part of Mars atmosphere, dumping it is not a problem. This oxygen production has already been demonstrated on Mars, the experiment was MOXIE, on Perseverance rover.

GW Johnson · 2024-08-05 08:20:35

Rob:

Well, rocket vehicles are an operational, flying technology. Done "right" with adequate development and testing behind them, you can bet lives on them. I was looking at only deployable technologies that you can bet lives upon. That is why I was looking at the "impossibility" of how to land a fully-fueled Mars Ascent Vehicle! In practice, you do it as a multi-stage thing, where only the upper stage(s) are the actual ascent vehicle. Sort of like the Apollo LM. But as a craft that must fly in an atmosphere (both ways).

The propellant production on Mars is simply not an operational, ready-to-deploy technology. It will take years and (at least) $10M's to make it ready to bet lives upon. That can be done, but it doesn't happen quickly, not if done "right".

It is always one hell of a long way from small scale feasibility demonstrations to an operational technology that you will be betting lives on. "Long way" means large amounts of both efforts/resources and time. I see nobody scaling this up and trying to shake the bugs out of it. And you can bet your life that those bugs are there! The time to find them and root them out is NOT while your survival depends upon that equipment on Mars!

THAT is the long pole in the tent for any of the mission concepts that requite making propellant on Mars. And that includes SpaceX as well as any of the Mars Direct notions. To my way of thinking, it is a very long pole indeed! That has been known for a long time, and yet I see nobody actually working that problem, when it is the real "killer".

GW

RobertDyck · 2024-08-05 09:43:24

NASA went from no humans ever entering space, to landing a man on the Moon in less than a decade. JFK's speech to Congress to land a man on the Moon was May 25, 1961. Apollo 11 landed July 24, 1969. That's 8 years. NASA could do it again. If NASA accepted Mars Direct in June 1990, we could have had humans on Mars by 1999. I would argue an unmanned test of equipment would land on Mars first in 1997. Earth-Mars launch opportunities are every 26 months. Life support proposed in 1968 for a Mars mission used the same principles as life support currently on ISS, so I would argue a push for Mars could have been done. I have also argued for an unmanned sample-return mission using ISPP, primarily to demonstrate technology for exactly the reason you stated. Technologies will not develop themselves, someone has to get off his big fat ass and do the work. "Old Space" contractors have gotten a hell of a lot of money during operation of Space Shuttle and everything since, more than enough to have done this work. Constantly complaining that it's "not ready" will not get the job done.

GW Johnson · 2024-08-05 10:04:30

Actually, Rob, I quite agree with you. Just don't expect anything out of "old space", and if I were you, I wouldn't expect anything out of NASA. Their track record since 1972 is actually NOT going anywhere but LEO, and the SLS/Orion/Artemis/Gateway thing is going to kill at least 1 crew, because there's nobody left who knows how to go further without killing somebody. All the ones who knew are long dead or retired. Which lack and that inevitable dead crew will put an end to NASA's space efforts as we know it. Today's NASA is very most definitely NOT the NASA of 1958-1972! Congress pretty much did them in, after 1972.

That puts it on "new space", and what I see there is some outfits more successful than others, but all of them in it up to their eyebrows just trying to fly things reliably. A lot of them won't be successful, because of the great difficulties. None of them are seriously working making propellants in situ, and none of them can work nuclear power, that being a government monopoly. There is some life support work going on, but not nearly enough.

For SpaceX, they got the Falcons going, then turned them into semi-reusable vehicles, and now they're in up to their eyebrows trying to make Starship/Superheavy work right! They are NOT putting any significant efforts into power supplies, life support, or making in situ propellants, because they can't! They are in way too deep at chronic overtime 70-80 hours/week, and they only hire people under 45 years old, who can put up with that for only a very few years. Which is EXACTLY why (1) they have high turnover, and (2) they keep having to learn from mistakes they made, while not learning from the mistakes made by others. That's been their pattern since they started.

I'm not complaining about the lack of progress in these mission-killing areas, I'm just observing. And I do not like what I see. For many years now.

If NASA were any good today, they'd be leading the necessary efforts toward propellant manufacture, power supplies, and life support with a bunch of contracts with "new space". But they can't, Congress won't let them, instead spending most of the money on pork-barrel projects that keep "old space" getting rich off corporate welfare while not actually accomplishing very much.

Without an effective NASA to lead the way, nothing useful is going on toward those 3 mission-killing lacks. THAT is what I observe!

GW

Last edited by GW Johnson (2024-08-05 10:08:21)

Oldfart1939 · 2024-08-05 16:58:06

GW has summed it up nicely in post #13!
The only other "pioneer" out there doing ANYTHING is Jarrod Isaacman by funding his Polaris Dawn series of missions, first to do a civilian spacewalk and visit the fringes of the Van Allen belts. This has at least caused some research and extensive development of new space suits. Isaacman has also offered to boost the orbit of the Hubble Space Telescope AT HIS OWN EXPENSE, but NASA has declined his offer of probably a $200 million mission.

Last edited by Oldfart1939 (2024-08-05 16:59:19)

tahanson43206 · 2024-08-05 21:12:30

This post does not have a direct connection to the topic, but it ** is ** a follow up on the post by Oldfart1939...

About Jared Isaacman
Jared Isaacman is the founder and CEO of Allentown, Pennsylvania-based payment processing firm Shift4 Payments.
Shift4 handles payments for a third of America's restaurants and hotels; Isaacman took it public in June 2020 and owns 38% of the stock.
He started the firm at age 16 in his parents' basement in Far Hills, New Jersey in 1999.
In 2011, he founded Draken International, a defense firm that trains Air Force pilots and owns the world's largest private fleet of military aircraft.
Isaacman sold a majority stake in Draken to Wall Street firm Blackstone in 2019 for a nine-figure sum.

This particular write up was (apparently) intended for readers of financial news, so it did not speculate about other interests.

However, I note that Isaacman is bullish on space prospects despite a possible downturn in the economy.

(th)

GW Johnson · 2024-09-03 10:58:24

Returning to the original topic, Starship/Superheavy is a rocket still early in flight test development. The Starship upper stage configuration still bears only superficial resemblance to what the final product might become. Estimates of its inert mass are still completely bogus, which makes the weight statements to be used in the rocket equation bogus as well.

Because of the exponential nature of the rocket equation, results are very sensitive to those weight statements that support any burn analyses. It's a GIGO thing, if you input garbage, you're going to get garbage. And THAT is precisely where we, SpaceX, or anybody else, are, when estimating what kind of performance to expect flying this thing anywhere, including Mars! There is no way around that.

I can put in weight statement numbers that indicate a Starship refilled on-orbit might take significant payload mass to Mars one-way. That ignores the rough-field landing issue, it ignores the propellant boiloff issue, it ignores the life support issue for any crew, it ignores the radiation protection issue for any crew, and it ignores the in-flight electrical power supply issue. It also ignores the electrical power issue on Mars. And it ignores the issue of an adequate heat shield, which is getting better, but still "not there yet" for an 8 km/s entry.

I can use those same weight statement numbers and reduce the return payload some, to show that a Starship refilled on Mars could fly single stage from the surface of Mars to a free-return at Earth. That ignores all the issues listed above, plus the issue of making propellant on Mars in situ. Which is a "biggie". So is the adequacy of a heat shield capable of free return at Earth, at something in the 12-17 km/s speed range! To the best of human knowledge, that requires ablatives. Refractory ceramics will not do that job! Which is what they are flying, as near as I can tell.

What I saw in the Nature article was way too many things assumed about inert masses and propellant losses, leading to inherently-bogus weight statements that correspond to the assumptions made. Their assumptions led to infeasibility. Other assumptions lead to feasibility. All assumptions anyone makes are currently bogus, and the rocket equation analysis is critically, drastically, sensitive to those assumptions. That's just the nature of the beast.

Basically, until better data become available, this is all "how many angels can dance on the head of a pin" crap. Give the flight tests a chance, and pray that Musk does not rush it too hard.

GW

Last edited by GW Johnson (2024-09-03 11:02:22)

Void · 2024-09-03 20:56:24

I will lead with my chin, and perhaps be required to accept the natural results for that.

I like to see the Starship to Mars as the Glass Full. An Olympic Objective. If it were I and I desired to be capable of achieving such a thing, then I do not want to give up on its potential of possibility.

But the simultaneous act of trying to make that adaptive to other tasks is also another good achievement.
We have the potential of up mass to orbit,
Point to Point travel, sub-orbital,
And I think 2 or 3 stage implementations inspired by Rocket Lab's Neutron Rocket.

I do not want to see SpaceX push Rocket Lab out of the market, and I don't think that they will.

But, I consider it obvious that a suborbital Starship, might do what the Neutron 1st Stage may do and host a very light 2nd stage to orbit.

And similarly a Superheavy, (Suborbital), might host a Starship Suborbital, with a 3rd stage orbital without reentry capability.

As Rocket Lab has opted for light weight materials, and SpaceX for Stainless for stages 1 & 2, but perhaps ? for stage 3, even so, I think that Rocket Lab keeps its special place in the Market.

But I deeply support the notion of keeping Starship also with the aspiration of the Olympic athlete that can in some cases go to Mars, and perhaps the Moon as well.

This is a form of tool making that we should continue to aspire to.

I have respect for the European Perspective, and the Russian and China perspectives, but we have our own distinct flavor of doing things, and getting wimpy, is perhaps a path to failure.

We should reach for the sky, as much as we can. Reality will enforce itself, even so. But reality can be changed as SpaceX has shown.

Ending Pending

Last edited by Void (2024-09-03 21:03:41)

Void · 2024-09-03 21:43:37

To take it just a bit further, imagine that both Rocket Lab and Relativity Space succeeded with their technology of the Neutron with 1st and 2nd Stage, and Terran-R, 1st and 2nd Stage.

With their technology, they might each build a 2nd or 3rd Stage from their abilities.

Keeping Starship Suborbital, may reduce the heat stress on Starship, while it may release a 2nd or 3rd Stage to go to orbit.

Rocket Lab has the most lightweight, but Terran-R 2nd stage might be possible to evolve into a Mini-Starship eventually.

This is not to say that you could not have a Starship to LEO that would refill these Neutron or Terran-R 2nd or 3rd stage devices.

And this may well profit any company involved.

And it reduces the burden that SpaceX needs to bear to achieve these things.

Ending Pending

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#1 2024-08-02 05:45:37

Article in Nature does not find Mars Starship missions feasible.

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