Manned Mars Mission

[Ophiolite]

Human psychology, I would've thought, to be a major factor in a trip to such a place.

Absolutely true. But you seem to making a commonplace error of assuming the psychology of all humans is the same as your psychology.

Personnel selection will be crucial to the success of the program. In the trilogy, Red Mars, Green Mars, Blue Mars by Kim Stanley Robinson, a character observes that to get selected for the colonisation program you have to prove you are sane; however, anyone who wants to go to Mars under the conditions they will live under is clearly mad.

These are huge challenges, but they are challenges that past history suggest can be met with some chance of success. (Not everyone is risk averse. Until the 1980s, when large scale guided expeditions on Everest became the norm, the chances of reaching the summit were about the same as dying on the mountain.)

 

Being locked up in a confined tin can, and then perhaps only a slightly bigger tin can whilst domiciled on a distant alien landscape with unbreathable air at an unsurvivable pressure (without the aid of a claustrophobic spacesuit), and the possibility, probably a high possibility, of being marooned is very serious test of human sanity..

1. The people who chose to go would not see this as being marooned.

2. You are assuming that over time the size of the living space would not increase.

3. You are overlooking the fascination many would have precisely because it was an alien environment.

If your location is anywhere near London UK, I'd suggest you go and view the Apollo 10 command capsule in the Science Museum. How they remained compos mentis confined in that thing I don't know.

You are expressing personal incredulity. That is irrelevant. I've seen the capsule. I've touched the capsule. I've done the same to the on display at the Johnson Space Centre in Houston and stuck my head inside one of the Mercury capsule when it was accessible in the '70s. My reaction was "Shoot, I wish I could have been in that.".

I recall a TV program whereby someone was being introduced to wearing a spacesuit (prior to a U2 flight). The guy freaked out. And even after said U2 flight he reported it being very difficult to endure. And enduring such confinement, I'd suggest, is nothing compared to a Mars trip.

Yet there were many U2 pilots, none of whom reported any issues. When I had an MRI scan I discovered I was claustrophobic. Guess what: many people are not.

[Enthalpy]

--------------- Launcher ---------------

I suggest there a flexible and hopefully cheap launcher design for the manned Mars mission
http://www.scienceforums.net/topic/65217-rocket-boosters-sail-back/#entry814958
its reused "sailback" first stage fits naturally a mission needing three or five launches.

I like to deploy the sunlight concentrators before leaving Earth orbit with a chemical engine. Referring to the sketch in the linked message, the launcher's previous stage can hold the Earth departure composite higher, say at its tanks; after separation, the concentrators can deploy, and if the chemical engine was over them, it can fire freely.

Zenit has rolls to guide a narrow and long stage separation. Good ideas should be copied.

----- Preset equipment: combine solar and chemical propulsion -----

I had suggested that a chemical engine may save mass at planetary escape or capture for using better the Oberth effect. Here are figures.

• Descent to a 3390+400km Martian orbit from 59970km apoapsis (48h period) takes 1249m/s provided by the Solar engine.
• Capture from asymptotic 2649m/s to the eccentric Martian orbit needs 831m/s, provided by an RL10-B.
• Escape Earth to asymptotic 2945m/s from an eccentric orbit with 127300km apogee (48h period) takes 673m/s from one or two RL10-B.
• Ascent to 127300km apogee from a circular 6366+400km needs 2897m/s provided by the Solar engine.

The Solar engine contributes 4146m/s at isp=12424m/s*90% (because its pushes are long), the RL10-B 1504m/s at isp=4565m/s. The same tanks and engines make the whole transfer: I take 100kg/t of propellants for them together. To preset 62t on a low Martian orbit, this scheme needs 139t on Leo instead of 159t and replaces some hydrogen by denser oxygen.

The fairing's sketch at the linked launcher description supposes this improved scheme.

Marc Schaefer, aka Enthalpy

 

[Endy0816]

What all are you proposing to use for radiation shielding and/or cellular damage prevention?

[Enthalpy]

I've not invested time in the protection of life against ionizing radiation. I checked the protection of electronic equipment for my satellite, but the requirements differ a lot.

 

The mission I propose, with its more efficient engines, travel in 80 days to and from Mars, which is a partial answer to the radiation worry.

 

I've also suggested to put a narrower shield only in the direction of the rays source, to reduce the emission of secondary rays, and save mass. There:

http://www.scienceforums.net/topic/80982-shield-astronauts/

 

The Solar thermal engine using hydrogen as a propellant, the tank can be a better shield.

 

Anyway, engineering without numbers is nothing, and I've put no figures on that. The 80 days travel was a desire by Nasa resulting from this radiation concern.

 

I considered opening a thread here to ask for data. If you have some information, you could put it on the forum. I suppose the topic deserves a specific thread, as it's vast.

[Enthalpy]

Here's how the descent-ascent module can look like.



Its oxidizer is Mon-33, or 33% NO in N₂O₄, because oxygen tanks fit badly in the module. 33% NO prevent freezing at -100°C but the toxic oxidizer has 8 bar vapour pressure at 298K. The fuel is farnesane or phytane, freezing at -100°C and safe; suggestion for synthesis there
http://www.chemicalforums.com/index.php?topic=56069.msg297847#msg297847

The module's skin needs some strength and thickness anyway, so it holds both propellants too, which help (141kg/m²) shield against radiations, especially after landing. The skins can consist of aluminium extrusions like described there
http://www.scienceforums.net/topic/60359-extruded-rocket-structure/
or of diffusion-bonded parts, or similar.

As the vessel's skin holds pressure easily, the engines are pressure-fed. Electric pumps and batteries would be possible
http://www.scienceforums.net/topic/73571-rocket-engine-with-electric-pumps/
or the original cycle that decomposes the Mon-33
http://www.scienceforums.net/topic/83156-exotic-pumping-cycles-for-rocket-engines/?p=805383

The astronauts bring bags, things like a dust sucker or motor brushes to fill the bags with Martian sand, wheelbarrows or some conveyor for local transport, and a crane to lay the bags on the module. 0.8m thickness adds 1100kg/m² shielding to Mars' atmosphere (162kg/m² at the Zenith). Compare with Earth's atmosphere: 2700kg/m² at airliners' 10km altitude.



I prefer this over a home printed on Mars in advance because the astronauts need no accurate landing.

Marc Schaefer, aka Enthalpy

[Delbert]

Just been reading that besides the reported reduction in bone density, a long period in zero G (space) can lead to permanent eyesight problems and cognitive degeneration!

 

Apparently these effects are consequent to the increase in cranial pressure that occurs in zero G. This increased pressure results in reduced oxygen uptake by the brain, which also increases pressure on the eyeball, leading to distortion and permanent retinal damage. Such that I understand some individuals returning from the ISS have now permanent eye damage.

 

So there you have it, probably go ga-ga and blind before one gets to Mars!

[Endy0816]

Can provide artificial gravity fairly easily. Normally cost and docking complexity is why we don't closer to home.

Edited December 7, 2015 by Endy0816

[Delbert]

Can provide artificial gravity fairly easily.

How? In practical terms that is.

[Enthalpy]

Thanks for your interest!

 

The transfers to and from Mars are to take 80 days in my scenario, which relies on the sunheat engine and on aerobraking, because of radiation concern. That's a short period for zero gravity: "long term" means rather a year now, with the record around 600 days.

[Endy0816]

Rotation is the main means commonly discussed.

 

https://en.wikipedia.org/wiki/Artificial_gravity#Rotation

 

I'm thinking in the real long term medical advances will provide a simpler solution. Should be possible to up/down regulate cell activity in bone production/reduction for instance.

[Enthalpy]

These elements of the descent-ascent module shield the astronauts:

• In Martian orbit and during the descent, the ascent propellants bring 190kg/m2 of O and N and the tanks 30kg/m2 of Al-Zn.
• Just after landing, the atmosphere offers 162kg/m2 of O and C at the Zenith. The astronauts sleep and shelter in the ascent module until they've built the sand walls. The room below the descent module shields decently too and is quickly accessible but unpressurized.
  • Propellants don't need to shield the descent module, only the ascent one.
• Once built, the sand wall brings 1100kg/m2 of O, Si, metals. The astronauts move in the descent module.
• Soon after take-off, no propellant shields the astronauts until they join the return vessel.
  • They accumulate dose and need luck for few hours. Apollo crews had luck for a week.
  • Extra shielding mass is best put at the bucket-seats, followed by the control panel above the astronauts.

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These skins and tanks are imperfect but let estimate the masses and engine pressures.



The frustrum's (and ceiling's) skin contains the ascent's Mon-33 in AA7022 tubes, spin-formed then milled into cones with integral stiffeners, for 1mm wall thickness and 2mm equivalent mass. Two layers of tubes are brazed together, transverse stiffeners welded on them, and sheets welded on the stiffeners, milled for 1mm wall thickness and 2mm equivalent mass. The tubes break at 68bar, the 36m2 frustrum and ceiling weigh 28kg/m2 or 1,0t.

Extrusions welded together compose the floor that holds the ascent's farnesane. 1mm thin AA6005A weighs 24kg/m2 or 0.6t and breaks at 67bar, allowing 29bar in the chamber.



Extrusions welded together compose the floor that holds the heavy descent's Mon-33. 1.5mm thin AA6082 weighs 2.6t and breaks at 139bar, allowing 61bar in the chamber.

A separate torus, Di=3.0m De=4.1m, holds the descent's farnesane - lighter combination than previously sketched. 2mm maraging weigh 0.3t and break at 146bar.

Extrusions welded together make the descent module's frustrum. They widen in steps to fit the cone, while milled parts make the tapers. 2mm thick AA7022A weighs 23kg/m2 or 2.0t and resists the sand's 100t easily.

Channels at <1bar separate the tanks from the air. Pumps reinject small leaks to the proper location, bigger leaks are vented. Maybe leaked Mon can be decomposed catalytically, but this is hot.

Some graphite tank holds the helium.

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There are many variants for the tanks and skins.

• Higher chamber pressures don't pay for the heavier tanks.
• Steel and titanium would need sheets too thin. I don't trust graphite fibres to retain the habitat's air.
• But aluminium sheets can be milled and diffusion-bonded to make a pseudo honeycomb sandwich that lets the propellants flow (sketch). Easier than extrusions at a frustrum, and not limited to Mars. Mind the materials compatibility.
• Sheets can be milled in a quilted shape and brazed or welded on a space truss assembled from tubes to make a sandwich (sketch). Easier than extrusions at a frustrum, and not limited to Mars.
• The ascent module can be smaller, with lighter walls and thicker propellant. It can be cylindrical (consider a fairing) for ease.
• Petals (or a ballute?) can stabilize the descent module and brake it instead of parachutes (sketch):
  http://www.scienceforums.net/topic/77901-controlled-aerobraking/
  rockets then brake from 400m/s without parachutes instead of 100m/s. The descent module can then be a cylinder with several floors.

 

 

----------

The descent engine pushes 1050kN in a D=1.25m nozzle. Expanding from 61bar to 73kPa, it achieves Isp=2760m/s=282s.

Braking 60t by 216m/s from the 400km Martian orbit leaves 55.5t, the 3.8t shield+parachutes 51.7t, 486m/s to brake and hop two times 43.3t landed. This consumes 12.9t propellants.

The ascent engine pushes 180kN in a D=1.1m nozzle. Expanding from 28bar to 12kPa, it achieves Isp=2962m/s=302s.

To bring 3.6t in the 400km Martian orbit, 4100m/s for ascent and manoeuvre need 14.4t at lift-off. This consumes 10.8t propellants.

Some 10t structure leave nearly 20t for the crew, their life support, tools, experiments.

I describe igniters for attitude control thrusters there:
http://forum.nasaspaceflight.com/index.php?topic=27308.msg849905#msg849905

but here's the sketch

 

----------

Other propulsion options include:

• Aza variants of the alkane. Easier to produce, 3s more efficient BUT hypergolic with Mon-33. Well, I'm not even sure if Mon-33 lights an alkane too.
• Oxygen would fit in a wide torus that can be vacuum-insulated. It has other drawbacks. Then, fuels cryogenic too would gain only 1t freight over farnesane.
• Batteries and electric pumps gain too little pressure to pay for their mass.
• But my Mon-33 recomposition cycle would achieve Isp=318s and 341s, gaining 3.5t freight
  http://www.scienceforums.net/topic/83156-exotic-pumping-cycles-for-rocket-engines/?p=805383
  is it responsive enough to land and hop?

Marc Schaefer, aka Enthalpy

Edited December 20, 2015 by Enthalpy

[Enthalpy]

And because the attached Xls have been lost here, I upload them again.

EarthCargoDeparture.xls

MarsCargoArrival.xls