Nerdy brain teaser (in space)

[susie_flo]

Good afternoon fiends,

Flabber my gast, we did a fun exercise at work this morning!  I know...   but really.  I did have fun.

So I wondered if any of you especially nerdylicious folk might like to have a go at it?  If so, click below...

(Although it is designed as a team exercise, you can do it on your own - just skip part 2)


Mission on the Moon – Part 1 (individual task)

Instructions:
You are a member of a space crew originally scheduled to rendezvous with a space ship on the lighted surface of the moon. Due to mechanical difficulties, however, your spacecraft was forced to land at a spot some 320 miles from the rendezvous point. During landing, much of the equipment aboard was damaged. Since your survival depends on reaching the spacecraft, the most critical items available must be chosen for the 320-mile trip.

The 15 items listed below were left intact and undamaged after the crash landing. Your task is to rank them in terms of their importance to your crew in allowing them to reach the rendezvous point. Place the number ‘1’ by the most important item, the number ‘2’ by the second most important, and so on through to number ‘15’, the least important. You have 15 minutes to complete this phase of the exercise on your own.

_____    Box of matches
_____    Food concentrate
_____    50 feet of nylon rope
_____    Parachute silk
_____    Portable heating unit
_____    Two .45 calibre pistols
_____    One case dehydrated milk
_____    Two 100 lb. tanks of oxygen
_____    Stellar map (of the Moon's constellation)
_____    Self-inflating life raft
_____    Magnetic compass
_____    20 litres of water
_____    Signal flares
_____    First Aid kit, including injection needles
_____    Solar-powered FM receiver-transmitter



Mission on the Moon – Part 2 (group task)

Your group is to employ the method of group consensus in reaching its decision.  This means each group member must agree upon the prediction for each of the 15 survival items before it becomes a part of the group decision. Consensus is difficult to reach, therefore not every ranking will meet with everyone's complete approval. Try, as a group, to make each ranking one with which all group members can at least partially agree. Here are some guides to use in reaching consensus:

1.   Avoid arguing for your own individual judgments. Approach the task on the basis of logic, not emotion.

2.   Avoid changing your mind only in order to reach agreement and avoid conflict.  Support only solutions with which you are able to agree.

3.   Avoid "conflict-reducing" techniques such as majority vote, consensus, averaging, or trading decisions.

4.   View differences of opinion as helpful rather than as a hindrance in decision-making.

 


Answers
I will post these in a separate post behind a cut, so that you can avoid looking until you're ready.
The answers are from NASA and come with a scoring system based on how close you were.

(The idea is that you mark your individual answers and also the ones as a group, to see whether working as a group has improved your performance)



EDIT: don't read comments until you've done the teaser (may contain spoilers)

Comments

[chiller.livejournal.com]

Ooo! This is fun!


10 Box of matches
7 Food concentrate
8 50 feet of nylon rope
9 Parachute silk
2 Portable heating unit
11 Two .45 calibre pistols
14 One case dehydrated milk
1 Two 100 lb. tanks of oxygen
5 Stellar map (of the Moon's constellation)
12 Self-inflating life raft
15 Magnetic compass
3 20 litres of water
6 Signal flares
13 First Aid kit, including injection needles
4 Solar-powered FM receiver-transmitter

The first three items are the things you'd die very quickly without. Four, five and six are essential navigation and communication aids - I'm assuming the signal flares are designed for space and don't require an atmosphere to ignite. Seven through nine are basic carrying things/survival things. 10, 11 and 12 are all useless without an atmosphere/oxygen. However, you have oxygen. Could a fired gun provide a means of quick but finite propulsion to get one over, say, a crevasse or mountain? It's worth a try, as the recoil should throw the person firing the gun as far as it throws the bullet. The first aid kit's needle could theoretically be used to hold open a valve on the oxygen tank and thereby questionably provide propulsion (or a massive and lethal explosion), if you applied a match to the jet of O2. Or to fill the body of the life raft with O2 in order to allow you to fire the gun.

I can't think of any use for a magnetic compass or a box of dehydrated milk.

[the-meanest-cat.livejournal.com]

Hee her, very well reasoned. It's fascinating seeing people's answers. If you haven't looked at the answers yet, I'd say it's worth doing part 2 with your flatmate, to see how you differ.

[chiller.livejournal.com]

Oooh, I might do that! It's quite interesting to see what people think will or won't work, on the Moon.

[the-meanest-cat.livejournal.com]

It made me realise how little I know about the moon!
(I could have sworn there was a thing about not being able to fire a gun in space... I'm glad I was wrong because the idea of propelling yourself over mountains by gunshot is so cool!)

[chiller.livejournal.com]

I would totally have given that a try. If it didn't work because of vacuum, you could theoretically create a little pocket of oxygen for it in the life raft and fire it from inside that.

I'm sort of astonished that vitamins etc are ranked so highly, because ... it's 350 miles over rough moon terrain in constant daylight with limited supplies. Of all the things you';re likely to be dead of by the end of the week, scurvy doesn't strike me as one of them.

[steer.livejournal.com]

I did not think a gun would fire in space either but apparently the wadding and material already in the bullet will provide sufficient oxygen for the explosion to take place.

[chiller.livejournal.com]

In a bullet, the explosion would be internal, but I would still think it relied on the bullet being entirely air-tight/vacuum-proof, and I didn't think they were (or why keep a gun out of the water, because if it goes into the water it won't fire?).

[steer.livejournal.com]

I would still think it relied on the bullet being entirely air-tight/vacuum-proof

Apparently unnecessary -- a strongly oxidising reaction will get O2 from whatever sources are available (in this case the gunpowder, wadding and so on). I didn't think this would work but then, in the initial stages of the reaction there's almost no free (atmospheric) O2 about anyway even on earth because it all happens so quickly.

[chiller.livejournal.com]

Cor, now I want a vacuum chamber and to run a few tests.

[steer.livejournal.com]

This video convinced me:
http://splodetv.com/firing-glock-underwater

[chiller.livejournal.com]

Oh, that is fun! Thanks!

[steer.livejournal.com]

the recoil should throw the person firing the gun as far as it throws the bullet

Only if the person in question has the same mass as a bullet.

[chiller.livejournal.com]

According to NASA, it works, as they suggest using the guns for propulsion in the answers...

[steer.livejournal.com]

It will certainly work to propel you. It was the assertion it would send you as far as it would send the bullet I was questioning -- this is wrong. It will propel you with a velocity proportional to the bullet's velocity and your mass ratios. For best results fire downwards at a 45 degree angle.

[chiller.livejournal.com]

My actual plan was to avoid having to try this out, by dint of being too cowardly and physically inept to ever make it onto a NASA mission, but in the event I am selected and forced, against my will, to man a mission to the Moon, I will use the gun to effect my escape while still on planet Earth.

Does the mass / proportional velocity thing apply because they're on the moon and in a gravity field, or would it apply equally in deep space, where there is nothing to stop one?

[steer.livejournal.com]

Does the mass / proportional velocity thing apply because they're on the moon and in a gravity field, or would it apply equally in deep space, where there is nothing to stop one?

It applies anywhere -- it's simply conservation of linear momentum. Assuming you and the bullet are initially "still" (not moving relative to each other) then the explosion causes the bullet to move with a given velocity in one direction -- this will cause you to move with a given velocity in the other direction. Think of the recoil from firing a rifle or shotgun (which is strong enough to give you a nasty bruise). In normal (earth) gravity you get a bit of a "kick" -- in low gravity apparently it's enough to propel you.

We can do some quick sums -- moon gravity is 1/6th that of earth = approx 10/6 m/s^2.

OK -- from wikipedia a .22 rifle has a muzzle vel of 330m/s and a bullet mass of 40g = 0.04kg

Person mass approx 100kg (assuming a quite fat person or a person with a heavy space suit). So we get the initial launch velocity of the person as 330*0.04/100 = 0.13 m/s -- not very impressive.

If we fire straight down then with that "launch velocity" we will "stop" after less than 0.22 seconds. 0.13*10/6

I think NASA are exaggerating or using a very very big gun.

[the-meanest-cat.livejournal.com]

"think NASA are exaggerating or using a very very big gun."
Imagine how cool it would be if you were using a bazooka!

[steer.livejournal.com]

Hmm... according to wikipedia most bazooka's are disappointingly recoilless. This is as well for the operator but not so good for our possibilities for lunar propulsion.

If we took this http://en.wikipedia.org/wiki/Carl_Gustav_recoilless_rifle
and modified it so it DID have recoil then we get a muzzle vel of 250m/s and 3kg ammo (according to Wikipedia).

This is much more satisfactory getting you a launch vel of your astronaut of 250*3/100 m/s = 7.5m/s

[chiller.livejournal.com]

A .45 calibre gun can generate muzzle velocities in excess of 400m/s, but it's not wildly impressive, is it? What you really want is a bazooka. Or a space ship that works.

[steer.livejournal.com]

Actually even worse than I thoguht because the mass of the bullet is 2.6 grams not 40 grams. (I thought gr stood for grams on the wikipedia page but it was "grains" some bonkers imperial measurement).

[chiller.livejournal.com]

Grains form the basis of most weight systems. ;)

[steer.livejournal.com]

Not weight systems you can use for actually working things out. :-)

[chiller.livejournal.com]

What, like ounces, pounds etc? ;>)

[steer.livejournal.com]

It's especially important not to use imperial measures in calculating your space-going stuff.

http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#The_metric.2Fimperial_mix-up

[chiller.livejournal.com]

Shades of "Spinal Tap", there.

[rosamicula.livejournal.com]

My year tens are doing this in the lesson as I type. And once agian they think I find hugely cool things for them to do.

[rosamicula.livejournal.com]

Oops, peaked too early! Thank you!

[the-meanest-cat.livejournal.com]

Happy to amuse your tens :-)

[whiteshadow.livejournal.com]

OK, I have not read the answer but my take on this are that the only three things that are important are the compass, the map and the receiver.

With this you can contact the spaceship who can then come out and rescue you ... after all they are undamaged and fully equiped!

D

[the-meanest-cat.livejournal.com]

It's a good theory. (You should take a look at the answers as it's quite interesting to see which items actually work on the moon and in what ways they are useful)

[kissmeforlonger.livejournal.com]

_____    Two 100 lb. tanks of oxygen
_____    Stellar map (of the Moon's constellation)
_____    Solar-powered FM receiver-transmitter
_____    Magnetic compass
_____    Signal flares
_____    20 litres of water
_____    One case dehydrated milk
_____    Food concentrate
_____    50 feet of nylon rope
_____    Parachute silk
_____    Portable heating unit
_____    First Aid kit, including injection needles
_____    Two .45 calibre pistols
_____    Box of matches
_____    Self-inflating life raft

I'm sure for people who know about science there are clever things you can do with the life raft, oxygen, parachutes and rope to create some way of travelling 320 miles really quickly. But I'm ignorant so hey ;-)