DU astronomy experts: The new, upcoming, human moon mission is said to be a rehearsal for a later...

[brush]

human mission to Mars. How long would a flight to Mars take? Weeks, months, a year? And how would the flight, if need be, and the subsequent Mars settlement, be replenished with food and water?

I do understand the settlement will be on the far side of the moon where there is ice because it's always in shadow and not subjected to the sun's rays.

[Walleye]

1. I always heard that it would take a year to get to Mars. I'm not an expert

[brush]

3. That's a long time. The space craft will have to carry a years-long load...

of provisions I guess, and a closely following craft will have to be sent to replenish the mission once it lands on Mars?

Fascinating stuff.

[Walleye]

14. I guess I won't ever see a woman elected president in my lifetime.I hope to see a woman walk on moon

I’m starting to hope now that I will live long enough to see Americans on the moon again

[keithbvadu2]

2. Matt Damon grew potatoes.

Matt Damon grew potatoes.

OK. A wee bit tongue-in-cheek there.

[irisblue]

9. I understood that reference

🥔 💩

[tinrobot]

4. Probably a two-year mission.

Mars' orbit places it close to Earth every two years. That's when we can launch and get there in the shortest amount of time - usually a 7 month voyage.

When they launch the return mission, they'll have to wait for the next two year window. So, 14 months getting there/back, and approx 10 months on Mars.

There's another way to do it where the astronauts are only on the surface for a week or two, so they can launch from Mars before the return window closes. That's a 14 month trip.

[brush]

5. Thanks for the info, tinrobot.

[Disaffected]

6. About seven months to get there

(with today's technology).

The "far" side of the moon is exposed to sunlight similarly to the "near" side ("day/night" cycle is one month long). The places always in shadow are in craters near the poles (where the sun don't shine).

[brush]

7. Ahhhh...thanks for the "where the sun don't shine" info.

And what are you telling me to put where?

[PCIntern]

15. I was going to say that the Moon's "dark side" is

exposed to the Sun, but we only see one side because of synchrony.

But we could send some Republicans on a mission to the Sun if they go at night.

[brush]

17. Heehee. I like that.

[ProfessorGAC]

8. If Launched From The Moon...

...they could achieve the speeds used in unmanned craft, which have taken around 4 months to go earth to Mars.
Theoretically, it could be done much quicker as a slingshot around earth would get the craft to over 28,000mph.
That's about 670,000 miles a day.
As Mars averages 142 million miles from the sun, and we're 93 million miles it could be done in 11 weeks.
But, they never do that.
We've had the capability to get a craft over 25,000mph since the late 60s, but it took 4 days to get Apollo 11 to get to the moon, which is only 2,500 mph.
I can do the simple math, but don't understand why it takes so long.

[muriel_volestrangler]

23. There's an instantaneous maximum speed just after a rocket boost, and an average speed

For instance, the maximum speed of Apollo 11, right after "translunar injection" - a short burst of the 3rd Saturn V stage to take Apollo out of Earth orbit - was about 25,000 mph. But after that, you're working against Earth's gravity. The spacecraft is basically like a ballistic missile, or even a stone that you've thrown up. It slows down. For Apollo, they gave it enough speed to get close enough to the Moon for the Moon's gravity to take over and accelerate it towards it. But the average speed works out well below the initial speed.

Similarly for Mars, you're also working against the Sun's gravity, once you've left the Earth-Moon system. And you need to get into orbit at the other end - either by using a rocket again (which means you had to carry a lot of fuel with you) or use Mars' atmosphere for braking (I don't know if anyone has come up with a feasible way of doing that yet*).

Looking at times to Mars, the 4 months was Mariner 7, which did a flyby, not going into orbit around Mars. Most missions have been just over 200 days.

Calculations of what's possible get very complicated - see a paper here, and look for the "pork chop plots" of departure and arrival times, and how much fuel is needed: https://www.researchgate.net/publication/281378287_Targeting_the_Martian_Moons_via_Direct_Insertion_into_Mars'_Orbit/download . To get into Figure 6's black "least fuel needed" (just 82% of total mass), you have to aim for the 200 day figure. And you need to deliver to the Mars surface a rocket capable of getting back into Mars' orbit.

*: Or you go straight for landing, which I think is what recent missions have done; but slowing down a vehicle through friction can be complicated, and this is a vehicle that needs to take off again, which SpaceX has done in Earth's atmosphere from Earth orbital speeds, but that doesn't necessarily transfer to a thin Martian atmosphere and interplanetary speeds - especially fast transfer ones.

[Takket]

10. good overview of the challenges and goals here......

https://en.wikipedia.org/wiki/Human_mission_to_Mars#Travel_to_Mars

[LunaSea]

11. Lunar ice is found at the poles

North and south, areas with the only permanent shadow.
Farside gets just as much sun as nearside.

Time to Mars depends on the propulsion and position of Mars to Earth at launch.
Liquid fuels=several months to a few years.
Ion propulsion= years to decades.
Nuclear steam= a couple of weeks.

[brush]

13. Nuclear steam?

[LunaSea]

27. Yes, nuclear steam rocket

http://www.neofuel.com/moonicerocket/


A nuclear-heated steam rocket engine (NSR) uses a nuclear reactor to convert water propellant to superheated steam. A pump raises the pressure of the water to about 3300 psi. Operation above the critical pressure avoids a propellant phase change and allows operation at higher power density. A rocket nozzle attached directly to the reactor converts the steam expansion pressure into thrust. The rocket vehicle consists of the nuclear engine, propellant water tank, nozzle, payload, and vehicle structure. Multiple restart capability and high reliability, similar to nuclear submarine propulsion systems, are essential.

[muriel_volestrangler]

29. I'd like to see the maths for "a couple of weeks"

because the link you gave wasn't about going to Mars, but about lifting off the Moon's surface, which is quite different.

To go from Earth to Mars in 14 days (about 1,200,000 seconds), a distance of, if you're not waiting years for the right opposition, say 80 million km, needs an average velocity of 67 km/s. With the specific impulse of 200 seconds that your link uses, getting a delta V of 67 km/s requires a ridiculous amount of propellant.

[LunaSea]

31. Yep, I should have said

"a few weeks", or "several weeks" to be accurate.
But my point was the time for such a trip depends on the type of propulsion.
The link provided a diagram illustrating the nuclear steam concept.
But there is much more at the Neofuel site-
http://neofuel.com/index_neofuel.html

[muriel_volestrangler]

33. The thing is the "nuclear steam" specific impulse is less than chemical rockets

and to get a fast trip to Mars, you need a higher specific impulse (like the VASIMR engine mentioned in this thread), not a lower one. Your link says

Or, do you just use it in a simple nuclear heated steam rocket, which performs poorly regarding rocket exhaust velocity, but delivers payloads in massive amounts when the mission delta_V is less than about 3 km/second?

The 200 second specific impulse of the nuclear steam rocket compares with 421 seconds for the hydrogen-fuelled engine used to send Apollo spacecraft to the Moon: https://en.wikipedia.org/wiki/Rocketdyne_J-2

A faster trip involves a larger delta V - more speed - and the rocket equation tells us you get that with either a larger specific impulse, or much more fuel (the fuel need goes up literally exponentially): https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

[Saboburns]

12. 8 months would be the quickest 1-way trip.

But that would rarely be the case.

But we will figure it out.

Because it's in our nature to be curious and wander.

[brooklynite]

16. What mission are you thinking of that involves a settlement on the moon?

Artemis, in 2024, will involve a one-week stay. Not largely different than Apollo.

[brush]

18. A NASA spokesman mentioned the moon mission is to be a...

rehearsal for a Mars mission and settlement.

[Effete Snob]

19. There is no side of the moon which is always dark

We refer to “the dark side of the moon” simply because the moon’s rotation is tidally locked by earth’s gravity such that we only see one side of the moon from earth.

But it is something of a misnomer, since there is no “dark side” of the moon. When we see a “full moon” it is dark on the other side of the moon. However, when we have a “new moon”, it is because the far side of the moon is illuminated.

Think about how an eclipse of the sun happens. You do understand that, during an eclipse, the new moon passes in front of the sun. Obviously, the far side of the moon is fully illuminated when that happens.

So, no, there is no side of the moon that is always dark.

There ARE, however some high- and low- latitude craters which are deep enough that their bottoms remain in shadow.

[brush]

21. Thanks for the info. Others have also enligtened me that areas...

near the moon's poles in craters have ice as their shadow areas don't get the sun's rays

[triron]

20. Plasma propulsion systems being developed by Ad Astra

Could get us to Mars in just 39 days.

[brush]

22. That's moving. How does it work?

[muriel_volestrangler]

24. See here for what's been achieved so far:

https://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket

According to Ad Astra as of 2015, the VX-200 engine requires 200 kW electrical power to produce 5 N of thrust, or 40 kW/N.[6] In contrast, the conventional NEXT ion thruster produces 0.327 N with only 7.7 kW, or 24 kW/N.[6] Electrically speaking, NEXT is almost twice as efficient, and successfully completed a 48,000 hours (5.5 years) test in December 2009.[8][9]

New problems also emerge with VASIMR, such as interaction with strong magnetic fields and thermal management. The inefficiency with which VASIMR operates generates substantial waste heat that needs to be channeled away without creating thermal overload and thermal stress. The superconducting electromagnets necessary to contain hot plasma generate tesla-range magnetic fields[10] that can cause problems with other onboard devices and produce unwanted torque by interaction with the magnetosphere. To counter this latter effect, two thruster units can be packaged with magnetic fields oriented in opposite directions, making a net zero-torque magnetic quadrupole.[11]

The required power generation technology for fast interplanetary travel does not currently exist and is not feasible with current state-of-the-art technology.[12]
...
In July 2021, Ad Astra announced the completion of a record-breaking test for the engine, running it for 28 hours at a power level of 82.5 kW.[28] A second test, conducted from July 12 to 16, successfully ran the engine for 88 hours at a power level of 80 kW.[29] Ad Astra anticipates conducting 100 kW power level tests in the second half of 2021.
...
In order to conduct an imagined crewed trip to Mars in 39 days,[32] the VASIMR would require an electrical power level far beyond anything currently possible.

On top of that, any power generation technology will produce waste heat. The necessary 200 megawatt reactor "with a power-to-mass density of 1,000 watts per kilogram" (Díaz quote) would require extremely efficient radiators to avoid the need for "football-field sized radiators" (Zubrin quote).[33]

https://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket

('NEXT' was used to send 'Dawn' to orbit 2 asteroids).

[brush]

25. Can the waste heat be used somehow?

[muriel_volestrangler]

28. No, it's something you need to get rid of

In space, there's no conduction or convection, so a craft either radiates it out, or it heats up. That's not a problem for low power systems, but 200 MW is a huge amount to radiate. As an example, a proposed robotic craft to go to Jupiter with a 200 kW fission reactor would have used over 400 square metres of radiators - it's most of what you see in the 60 metre-long craft: https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Orbiter

and a 200 MW system needs to dump 1000 times the heat.

[LastDemocratInSC]

26. The first lunar landing of the Artemis program

will be near Shackleton crater at the South Pole.

[Hermit-The-Prog]

30. Just skip the sports cars and go straight to a Winnebago

Build a big camper in lunar orbit, load it up for a long vacation, and head for Mars in comfort. A few tons of lunar rock can provide the fuel -- eject it as dust for propulsion.

The bigger the ship, the more comfort on the way and when you get there. Send a taxi to change crews.

[Shanti Shanti Shanti]

32. Um, the far side of the moon is always dark, TO US, not the sun. Sunlight falls equally all over it.

The moon is tidal locked to the earth, so WE only see one side, but the earth/moon system spins around in space while orbiting the sun.

The icy region at the south pole of the moon is what the Chinese are targetting, so we are in a race to get the ice too.