Forty 40 Ton Mars Delivery Mechanism

GW Johnson · 2024-02-22 10:29:14

What I did was size a 1-shot lander and transfer stages (reusable or nonreusable) to send it to Mars. The 1-shot lander has to drop its 1-shot thin ablative heat shield to fire up its landing engines and unfold its legs.

If instead equipped with a segmented low-density ceramic heat shield that folded out of the way, it could be refueled with propellants made on Mars (I did my design with storables NTO-MMH!!!!) and flown again. There is no concept for how to make those propellants on Mars, though. And the loaded-with-cargo dV capability was quite low at 1.05 to 1.4 km/s, in order to put 40 tons of cargo into a vehicle massing about 80 tons at Mars entry. With that low a dV capability, I do not know what it could be reused for. What's the point of flying unloaded?

I did it with storables because I am definitely NOT a believer in long term storage of cryogens without serious or even fatal evaporation losses, unless substantial cooling power is available, which is also added mass. LCH4 is not as bad at evaporating and leaking as LH2, and it is worse than LOX, but they all have evaporation loss rates, even from a Dewar.

The reusable transfer stage design that used LOX-LH2 used the header tank construction within main tanks, to make the vented main tank into essentially a Dewar outer vessel around the inner header vessels. That buys you more time and a lower refrigeration requirement for months or years in space with cryogens. The reusable transfer stage would spend about 3.5 years in space before it could enter LEO for recovery. It is one hell of a risk to take, to get a reusable design.

To my knowledge there are no ready-to-use long-term re-liquifaction technologies available, to make years in space possible with LH2 or even LCH4. There are only lab benchtop demo toys. There's light-years' of development effort between a bench-top toy and a real, usable technology. I know that is an unpopular thing to say, but it is VERY TRUE!

Probably the most ready-to-build-and-test portion of my study is the lander and the non-reusable transfer stage. No long-term cryo storage was involved. Only departure from LEO was with LOX-LH2. The rest was all storables.

The lander would be sitting there to salvage. It would contain some amount of unused storable propellant that could be recovered and used elsewhere. The transfer stage would crash after suffering severe entry heating damage. It would not be salvageable in any sense.

GW

Last edited by GW Johnson (2024-02-22 10:33:51)

Calliban · 2024-02-22 11:35:07

Some potential long-term storable liquid propellants that we can talk about making on Mars.

Fuels: Propane, Butane, methanol, dimethyl ether. Methanol can be synthesised using using the same chemical reactor technology used to make methane. The catalysts are different and the CO and H2 are fed into the reactor in different proportions. Dimethyl ether has a vapour pressure similar to propane at room temperature. It is made from a condensation reaction between two methanol molecules over a catalyst. Any methanol producing sabateur reaction will also produce DME. But higher DME selectivity can be designed for.

Oxidants: LoX, HNO3, N2O, NO2, H2O2, F2. LOX and F2 give the highest exhaust velocity. F2 is so toxic that it just isn't a serious contender. Concentrated nitric acid is a metastable liquid and is 40% denser than water. But is very corrosive. Even 316SS has a limited life exposed to it. Under standard conditions, it will evolve NO2, which will form a gas over its surface. H2O2 has stability issues that can be reduced via chilling. I have heard of N2O (laughing gas) used as oxidiser. Energy density is reduced and from memory, there were problems with ignitability. But it is storable as a saturated liquid at room temperature and this is its selling point. I don't know much about NO2, aside from its toxicity.

Last edited by Calliban (2024-02-22 11:39:00)

SpaceNut · 2024-02-23 20:05:07

Here is the Marco polo topic first link for fuel manufacturing lander for mars.

https://kiss.caltech.edu/workshops/isru … anders.pdf

SpaceNut · 2024-02-25 16:55:26

cargo 1 way can go to orbit if we wanted, to the surface to support and for cyclical orbital if that's the thing we are looking for, but we need to know what we are sending as each items has a different density to volume.

With the ship characteristic nailed down we can then determine what goes, how much and how long it can support for any of the three uses.

tahanson43206 · 2024-02-25 20:50:45

For SpaceNut re #54

You don't ** have ** to say something just to fill a post.

This topic is about plans for landing 40 tons on Mars. Your post #53 with the link to just such a plan is a good fit for this topic.

Your hand waving in Post #54 has nothing to do with the topic, and it is not needed. No one who reads this topic to learn about landing a 40 ton payload on Mars will get anything out of Post #54.

If you want to help the topic, please do as you did with the link to the article you showed us in Post #53.

(th)

SpaceNut · 2024-02-26 19:34:41

Hand waving for shuttle was ignored and that leads to failure.

volume metrics at work

img.jpg?width=1200&height=628

A softball measures between 11.88 and 12.13 inches in circumference and weighs between 6.25 and 7.00 ounces;
a baseball measures between 9.00 and 9.25 inches in circumference and weighs between 5.00 and 5.25 ounces.

Both are under 10 ounce for payload not broken but a ship designed with small diameter means just a baseball, but we need softballs which cannot ship which means altering the design.

Design is more than engines, fuel, oxidizer, tanks, landing support to surface items as this requires stated inside cargo area dimensions. As you need other Craft support items in communications, telemetry, sensors, power sources to keep craft functioning ant that is not nuclear. Then again, a nuclear option for the fuel making plant is something that can be swapped in later.

My posts give these in those documents

The cargo bay of Starship is approximately 650 cubic meters in volume. Sure it can have 100 to 150 mT at one time of things we know we need for the crewed landing to follow. Pioneer Astronautics demonstrated a reactor capable of producing 1 Kg a day of methalox fuel from hydrogen and carbon dioxide while consuming a power of 700W. For 710 tons in 400 days that is 1.89 MW. (Zubrin et al., 2013)
Assuming 400 days to produce the 710 tons of fuel needed, 352 tons of water (for electrolysis) and 1.89 MW of power would be needed. Using the methods and assumptions detailed in section 4.3 (including a 20% margin for safety), the solar infrastructure would be:
• 229.2 tons in mass.
• 3437.4 cubic meters in volume.
• 57290.1 square meters in area.
The deployment would require 5 to 6 Starships (volume constrained) and significant deployment operations and maintenance.

We all thought that this many were to many and yet it takes that many per each ship to refuel before leaving earth to go to mars. My topic for getting the fuel from the ground gave those same quantities of ships to land on mars. Of course, crew support required 2 more ships to land with them to be able to do a 500-day surface mission for 100 people.

. Power remains one of the most significant challenges of a Mars mission architecture that accounts for the return of the astronauts. As with issue 1, failure in this area would result in loss of crew.

Of course, nuclear can go out as cargo that is not active until deployed in any of the ships that have room for it once on the surface with crew setup.

Then there are the needs for landing area conditions to be just right as we have seen with the moon landing failures.

You can see that the second ship is less capable of mass, and it does not have the volume to be able to do so.

The much smaller ship is more like the 40 mT design to mars but even that is a much smaller crew size and with other goals. Caravel class naval ships on Christopher Columbus’ first voyage to America

Pinta. Cargo on board (Total: 26.5t):
• Water tanker rover. Mass budget: 3.5t
• Food, water and supplies. Mass budget: 6t
• 20 KW of solar panels: Mass budget: 2t
• Scientific equipment, batteries, carbon dioxide electrolyzers and other. Mass budget: 15t
Santa María (uncrewed) Cargo on board (Total: 120t):
• Cranes, batteries and all operating equipment. Mass budget: 8t
First Martian habitat, including crew quarters and a common area. Mass budget: 34t
• Pressurized Rover. Mass budget: 10t
• Water extraction/ice mining machinery. Mass budget: 20t
• Extra water and supplies: Mass budget: 12t
• Additional solar panels/fission reactors. Mass budget: 36t

GW Johnson · 2024-02-27 09:23:44

Try looking at it this way. Starting from LEO, it takes about 3.7-3.8 km/s worth of delivered dV to cover the departure onto a min-energy Hohmann transfer to Mars (closer to 4+ if faster) plus two course corrections along the way, which dV has to come from something.

Once you are there, you have two simple options, and you have to come up with more complicated schemes if you dislike both simple options. Option 1: decelerate into LMO where the surface is within easy reach. That cost is variable due to Mars's orbital eccentricity, but is on the order of 2 km/s. Option 2: enter Mars's atmosphere directly for as much aerobraking as you can achieve, and then do a rocket-powered landing because the air is too thin, and your end-of-hypersonics altitude with a big object is too low, for getting any help out of chutes. That dV is on the order of 1 km/s, which makes this the cheaper option in terms of dV-to-ship.

Now, logistics:

With option 1, if you want to take the cargo down to the surface, then you have to go and get it somehow. It's complicated, but crudely speaking, your orbit taxi will need around 5 km/s unladen dV capability to cover launch into orbit from the surface, plus a maneuver kitty to rendezvous. Then it will need about 1.1-1.2 km/s worth of dV capability fully laden with the shipped cargo, to cover deorbit, and the final rocket-powered landing. That's 3.7-3.8 km/s to put it on course for Mars, about 2 km/s to enter LMO, then about 6.1-6.2 km/s more to go and get it with an orbit taxi to the surface. You cannot add these dV's, because the weight statements are all different, but the clear implication is that you will use a lot of propellant doing this, just to get your cargo onto the surface of Mars, because the incorrect summing gets you 11.8-12.0 km/s. That's true whether some of the propellant is made at Mars, or not.

With option 2, the cargo is already on the surface! It took 3.7-3.8 km/s to put it on course for Mars, and about 1 km/s to land it there. Again, you cannot add those dV's because the weight statements are different, but the clear implication is that takes a lot less propellant, to put your cargo onto the surface of Mars, because the incorrect summing gets you only 4.7-4.8 km/s.

Exactly how you go about doing either option can make the actual propellant quantities vary, but only by percentages, not factors of 2+! And THAT is exactly why SpaceX decided it could use Starship with big payloads to go to Mars with direct entry and landing, but did not really consider going to LMO instead. But, in so choosing, they gave up any surface scouting for the best place to land, instead just having to pick a spot and go there blind to any real ground truth.

Those are the kinds of tradeoffs you have to make to choose between the two options, or considering any more complicated alternatives (each of which is likely to have an even higher incorrectly-summed dV). Those are the kinds of tradeoffs that can get crews killed, because the disparity between remote sensing and ground truth is still non-zero, despite what everyone so desperately wants to believe.

The kind of "ground truth" I refer to is subsurface: what resources are buried there, and how best do we recover them, and how best can we make use of them? Wrong answers to any of those questions can kill. None of the landers and rovers we have ever sent to Mars can answer questions like that!

Myself, I prefer option 2 (direct entry and landing) for bulk cargo and big hab items, for a real base. But I want to see some surface/subsurface scouting done, before I have to pick a final site for building a base. That kind of scouting is better done as multiple short landings at multiple sites, from a single mission based in LMO. The bad news: you cannot really do both in the same mission!

And if you just mount a big base-building mission to a site picked from remote sensing, you are betting your crew's lives that it is the right site, that your remote sensing was 100% accurate. The history of real ground truth vs remote sensing refutes that assumption.

GW

Last edited by GW Johnson (2024-02-27 15:48:24)

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Re: Forty 40 Ton Mars Delivery Mechanism

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Re: Forty 40 Ton Mars Delivery Mechanism

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