MISSION LOG – SOL 480
Hermes message of the day: “We can’t see your rover on the surface anymore. The storm is too thick. The center of the storm is about two hundred kilometers due east of you, but the edges… well, the storm covers a huge portion of the planet now, Mark. All we can suggest is that you try disengaging two of the wheel clutches, while you’re still on comparatively level ground, and see if that saves power.”
Yeah, already did that, after we woke up this morning and found we’d only managed to recharge up to 71% of total battery capacity. It didn’t help worth a damn. We still only managed 51.8 kilometers today.
If we’d made a proper full sol of driving, we would have had to turn east or west to get around Crommelin crater today. We’ll probably just barely reach it tomorrow. After that we have to make some hard decisions.
Before we put out the solar panels today, we tried running on magic power. The ship has a magic-to-electricity converter in the bridge controls, where the emergency magic batteries normally connect. We hooked one magic battery into the system today and began driving on it. After about a minute and a half Starlight called a halt to the experiment, because she could watch the charge readout dropping as we rolled. We were burning through mana that fast.
After we set out the solar panels (now operating at a measly 59% of peak), we checked the levels in the battery we used and the distance we traveled in a minute and a half (accelerating most of the way, admittedly). Then we did the math and worked this out.
In very rough, round numbers, the Whinnybago burns twenty kilowatts per hour driving at top speed. That’s a kilowatt every three minutes.
In the minute and a half we spent driving on magic power, we only hit top speed for about half that time. It takes the Whinnybago a long run-up to get started. So we only traveled about half a kilometer, burning (again, very rough, round numbers) five hundred watts in that time.
In that time, the battery went from fully charged to 95% charged.
Put another way: the battery would get us ten kilometers before it pooped out. It would only run for a bit more than twenty minutes. It’s effectively the equivalent of a battery with a watt-hours rating of about ten kilowatt-hours.
Give it its due- that’s more efficient for a lot less weight than the rover batteries, and it competes with the lighter weight but much bulkier Hab batteries. But considering I’ve seen Starlight do things with fractions of magic battery power that would rate in megawatts or possibly gigawatts if they could be done at all electrically, I’ve got to say that the magic-to-electricity converter is really fucking inefficient.
But that’s not really the problem. The problem is recharge time.
If not for the dust storm, we’d have a little over 70 pirate-ninjas of recharge power every sol, of which we can only store 54 pirate-ninjas. Every sol we’d start out with another seventy kilometers or so of driving in the tank.
If we hooked all twenty-one of the small magic batteries up to the rover power system and used it only for driving, we’d get two hundred and ten kilometers out of it. The batteries are currently recharging at a rate of one point four percent per sol… which means a full recharge from zero would take sixty-seven sols.
Sixty. Seven. Sols.
During which time we could do nothing, absolutely nothing, involving magic.
During which time the jumbo batteries would be losing charge at the rate of 0.5% of a regular battery per day… each.
During which time Dragonfly begins drifting back towards physical collapse.
We would have to be really fucking desperate to take that option. And we would also have to be a lot closer to the Hab or Schiaparelli than we currently are. As it is, we are now slightly closer to the MAV than to the Hab or the cave farm. If two hundred kilometers got us to safety, it might be worth it. Otherwise, better to save the magic for a better idea.
Let’s just hope we find one before we lose all light completely.
By the way, if you say, “Why not just use the magic batteries to drive the distance they recharge by?” All twenty-one batteries gain about 1.4% of their capacity each sol. That adds up, combined, to the equivalent of 29.4% of the charge of a single battery, or just under three kilometers. Under the current conditions (technical definition: “fucked nine ways from Sunday”) it’s not worth it.
Better to keep the changeling, dragon, and ponies healthy with that power… while we can.
AMICITAS FLIGHT THREE – MISSION DAY 490
ARES III SOL 481
The wind didn’t howl outside the Whinnybago. The dust didn’t hiss as it hit the bare ship hull. The only electricity came from the flickering glow that appeared occasionally on the tungsten discharge points attached to outer hull mounts around the former Amicitas, some of which were visible through the bridge windows.
But the dusty haze of the prior few sols had become a fog, a cloud of dust motes drifting past on the weak Martian wind. The afternoon sun shone dimly outside, providing a light more similar to what the ponies thought of as moonlight than anything associated with a star. The storm had them firmly in its grip.
And considering that they’d only driven thirty-six kilometers before running out of power, and that the solar panels which produced that power provided only forty-two percent of what they should have produced, everyone in the Whinnybago recognized that grip was tightening.
Hermes had run out of hopeful news. Their report today had been grim; center of storm one hundred forty kilometers east-northeast. Storm almost stationary, no longer widening but getting thicker at the core. At the storm’s center, they estimated, only about ten percent of the sun’s light reached the Martian surface… ten percent and still dropping. If the storm remained at current strength and intensity, it would take over a month to pass over Crommelin crater, which the broken ground outside suggested was now very close by the Whinnybago.
“So here’s the situation,” Mark said, as the six of them gathered in the bridge to discuss options. “We have three options. We can hunker down and hope the storm passes more quickly than expected. Anybody want to talk about how likely that is?”
Not a word. Everyone knew this storm had their names on it.
“Yeah, me neither. Option two; turn east-southeast and begin making for Schiaparelli at whatever speed we can. That takes us closer to the heart of the storm, but it also runs against the direction the storm’s currently moving, so it’s just possible that we get out from under it sooner. We can run life support off the RTG and your ship’s system, so we should be able to at least crawl a little each sol.”
“Maybe we could pull the ship behind us,” Cherry Berry suggested. “Like when it was salvaged.”
Fireball slammed a fist into the deck. “No!” he shouted. “Tying ropes around our space suits? The way they are? Look at us!” He pointed to the patches on his own suit, the elbow and knees on Cherry and Spitfire, the large gash of black gunk of Starlight Glimmer’s right foreleg. “They blow out quick. Kill wearer. No rescue. Suicide. Dumb idea. I know what I’m talking about.”
“I could make harnesses-“ Dragonfly suggested.
“NO!” Fireball took a deep breath, held up a palm to stop anyone from speaking, and thought carefully. “Even harness make different pressure on some parts of suit than others,” he said. “Different pressure puts more pressure on patches. Can’t avoid. Can’t fix. Trying that will kill somebody. Listen to me.”
Dragonfly nodded. “I hear you, Fireball,” she said, “but if it comes down to the choice-“
“If it’s choice, then ask Mark for medicine,” Fireball snarled. “You want a choice of how to kill yourself, he find something a lot less trouble than losing all your air outside.”
“Okay,” Mark said after nobody followed up Fireball’s declaration. “Anybody like that option? My main problem with it is, if my navigation is right, we’re still about thirteen hundred kilometers from the entrance to Schiaparelli, plus maybe another four hundred kilometers after that to get to the MAV. Seventeen hundred kilometers. If we traveled at the rate we did today, we’d reach there on Sol 530- but we all know the storm would get a lot worse. My math says, we’d miss the launch date and run out of food first.”
Again, no argument.
“Option three. Go around Crommelin to the southeast. We have another hundred and fifty kilometers of southward travel before Pythagoras becomes our enemy- sorry, cultural reference, I meant before we start getting farther away from Schiaparelli instead of closer. So long as the storm doesn’t turn south and cross the equator- which it’s not supposed to be able to do, but who knows what this fucking planet will do next- we’d begin to get out from under the shadow.
"The problem is, we don’t know how far south we’d have to go. The dust cloud extends a long way south of the equator- maybe eight hundred kilometers. If we go that route we’d have to take the backup route into Schiaparelli on the southwest side, which requires crossing a lot of uneven, rugged terrain. It’ll take a long time, and there’s no guarantee we’d reach the MAV before our food runs out.”
“There’s a fourth option,” Starlight said quietly. “I’ve been thinking about it for the last two sols.”
“What is it?”
Starlight shuffled her forehooves on the deck. “Remember the booster system test?” she asked. “It cleared the skies instantly. We had weeks of clear weather and unseasonably warm temperatures. We could do it again.”
“Hey, yeah,” Dragonfly said, grinning. “That is a great idea! We don’t need as big a mass this time! Or as much speed, either! All we need is a big rock from the surface, a little booster target, a booster crystal, and some battery power!”
“We’ve got half a ton of clean crystal,” Starlight said. “I think we only need twenty-five kilos of it to make the booster and its target.”
“We still have the data from the test,” Dragonfly said. “We can use that to keep the power use to a minimum. Maybe only one battery would do it!”
“Yes!” Starlight grinned even wider than Dragonfly now. “I can’t think of any reason this might go wrong!”
“I can,” Fireball grumbled. “How do we know the last test didn’t cause this storm now?”
Grins vanished. The others looked meaningfully at one another.
Cherry Berry finally spoke up. “So maybe we have a storm during launch day,” she said. “We’ll deal with that then. But if we don’t try something, this storm right now will keep us from even having a launch day.” She looked at Starlight. “Do it,” she said. “We’ll launch your cloudbuster tomorrow morning.”
I have a baaad feeling about this..
Prediction: The Cloudbuster turns the storm from a weak dust storm into something closer to a damn hurricane, and it almost kills all of them. But then Mars' fury is expended, the storm is gone, and they can pick up the pieces and keep going- even if the they're working with barely enough supplies to make it.
Starlight, Starlight, Starlight, that's just asking for trouble.
Am I the only one concerned that Fireball knows suicide by overdose...
9147728
She invoked Murphy... And Murphy wants them dead, but at the same time more magic in the environment is closer to Terraform so this will be interesting
9147709
Well, they're screwed if they do and they're screwed if they don't. Might as well go with the boost.
watt is a unit of energy/time. so watt/hour is a unit of energy/time², a.k.a the change in energy use.
So if the rover "burns" 20 kW/hour, it's energy use changes by 20kW every hour, which would be very strange
Starlight, you're a genius.
9147709
You're not the only one.
You know, scientific analysis of personfication aside, this is the point where it REALLY matters whether Mars is malevolent or if magic just makes the weather weird. If magic just makes the weather weird, in a way that make it looks like it's aimed at them, then the cloudbuster is the right move. They can assume the results will be replicated.
On the other hand, if Mars is actually malevolent, then it comes down to what it wants to do. Right now it has them dead to rights. I assumed the unseasonable weather and clear skies after the last launch were Mars taking the power they gave it and using it to wind up a punch. That being the case, doing another launch test won't affect this storm AND will give it the juice for something else.
So yeah. We'll see how the Stormfather responds, and can add this as evidence of whether he really exists.
...I wonder if it's possible to infuse Pegasus weather magic in the cloudbuster somehow.
9147743
Yes. This is the place the pirateninjas should come out and play.
9147751
Cue the mummy storm.
cdn1us.denofgeek.com/sites/denofgeekus/files/styles/article_width/public/2017/06/the_mummy_sandstorm.jpg?itok=THWhgfqf
I was hoping that would come back into play.
9147709
"In very rough, round numbers, the Whinnybago burns twenty kilowatts per hour driving at top speed. That’s a kilowatt every three minutes. "
This violates laws of physics because kilowatts measure the speed of energy transfer, not how much energy has been transferred.
I think here you want kilowatt-hours, kWh.
9147330
Ah, thanks; I wasn't sure whether you were talking about a separate section or had just hit the i key instead of the o.
"the Whinnybago burns twenty kilowatts per hour driving at top speed. That’s a kilowatt every three minutes"
Would those both work out to J/(s^2), though? Is Mark just using using the wrong words in the log?
"So we only traveled about half a kilometer, burning (again, very rough, round numbers) five hundred watts in that time"
Here he also uses watts instead of joules (or watt-hours).
These horses are going to die because the only crewmember who knows what electricity is can't calculate power consumption properly.
Right, ok, yeah, I guess that's an option then. It was really strange reading Starlight and Dragonfly getting excited about it without thinking they were being sarcastic, given how Starlight seemed so reluctant to mention it. If it works, though, they can always launch another booster the day before launch and clear the skies until they're long gone.
9147794
9147743
9147789
Yes, yes, I know. The thing is, the original novel never refers to the energy storage capacity of the rover in anything other than kilowatts or pirate-ninjas (a kilowatt derivative). No volts, no amps, no joules. If I want to quantify energy usage at all in this story, I'm pretty much locked in to perpetuating the errors of the book on this point.
No possible way that could go wrong.
Here's another potential solution. The problem with using magic to power the rover wasn't the level of available magic power, it was the fact that the magic to electricity converter was astoundingly inefficient (no need to worry about magical abundance in equestria I guess). But, there's more than one way to convert magical power into electricity. Based on most fandom's magical cannon, a light spell is considered very basic and not very energy intensive (it's a beginners spell). What if Starlight used a light generating spell to power the solar panels directly? This would obviously be extremely inefficient, even more so depending on how energy intensive the spell is. But, assuming that (based on Mark's statement) the 5% can roughly translate into a Megawatt, assuming say a 10% energy efficiency of converting magic into light, and a 20% efficient solar panel, that translates to 20,000 watts of power. If they're only able to collect say 1/5 of that, that's still 4,000 watts of power right there, which is 8x better than the magic to electricity converter. Therefore, if they only drive the distance the batteries recharge by per sol, using that method, they could add an extremely conservative 24km to their driving distance. Added on top of what they can get naturally, They'd average something like 60 km/sol at the moment, which could be even better if the spells are more efficient, or the magic% to energy ratio is higher.
I don't have the time right now to really work out the math to see if this would actually work, or if that'd be enough to get them to the MAV while still alive, so if anyone sees a flaw in this plan, or if any of my estimates seem unreasonable, let me know.
9147731
Nope.....
Operation Pegasus is go for launch.
9147818
No you're not "locked in" to anything, you're the one writing this.
What we are telling you is that you cannot quantify energy storage capacity in kilowatts, because that's not what they measure. Kilowatts are a per second measurement of consumption speed.
I don't know what a "pirate-ninja" is (or even what airport novel you're cribbing), but it's probably equivalent to kilowatt-hours which are a real thing that exist and makes sense. You even use them a few lines down:
"Put another way: the battery would get us ten kilometers before it pooped out. It would only run for a bit more than twenty minutes. It’s effectively the equivalent of a battery with a watt-hours rating of about ten kilowatt-hours. "
9147830
simple solution: multiply or divide by time when necessary
9147818
Ah. Well, annoying, but understandable; thanks for the explanation. I wonder what led Mark to make this error, though? I mean, sure, he's not an electrician or electrical engineer or something, but he is an astronaut; I'd think they'd have covered this.
9147830
The airport novel is the book this is a crossover with. Maybe cool it with the hostility a little? Science is hard.
9147819
That's an interesting idea. You'd need to experiment. I have a hard time believing the efficiency would beat the electricity magic converter but it's not impossible and worth testing.
Here's another one though. What if, instead of using a light spell, they use telekinesis to spin the motor as a generator? As Mark says, Starlight has really intense energy output.
In fact we don't even need magic for that do we, if they can rig a way to spin the wheels (off the ground obviously) efficiently with muscle power.
Hopefully, a simple way of launching at the right time to miss everything important, is to do it at night, when theyre facing away from the sun and all the delicate stuff heading their way? Trouble then is making sure Phobos and Deimos is preferably elsewhere as well?
Might not get the Kate Bush, Cloudbusting link, but given the CSP and desperation, looks like theyre going Chemical Brothers, Right Here, Right Now.
I just get this image of testing Orion drive plate by slamming it down with a multithousand ton steam hammer just as the explosive drive pulse goes off between the hammer of the drive plate and the anvil. Sure the drive pulse clears a gap, but that hammer is still coming down, and if the pulse is exactly the wrong size, then the reflected pulse is going to amplify the hammer.
Will the Primary Launch pulse be large enough magical discharge for Twilight to lock on to, given that amount of magical drive pulse in Mars atmosphere is going straight out of global dust storm territory?
9147842
Thanks, yeah a lot of the critical factors would have to be experimentally quantified. I'd have a hard time believing that too, but it said that they were getting 500 watts for the equivalent of at least megawatts of input power. Maybe the converter was designed for high output but low efficiency, which would make sense if it was designed for an environment where it's fuel source was as abundant as air. Still an insanely low efficiency, but not completely unthinkable.
9147859 The magic battery, using very vague estimates, is the equivalent of a 10 kWh battery- slightly better, and a lot smaller and lighter, than the six batteries used by the Whinnybago. Unfortunately, they don't have a widget to convert electricity into magic...
9147841 My question is, why didn't Andy Weir use joules, amps, volts, etc. instead of kilowatts and kilowatt-hours?
So far so good, what Sol would they be at when they launch off of Mars, I haven't seen the movie since I saw it in theater so I forgot quite a bit of it along with when Mark finally gets off the planet.
9147819
I don't follow the math here so just from a layman's perspective; it just seems intuitively wrong that adding an extra step to the conversion process would actually save energy. Wouldn't the entropy of the extra step cause even more loss?
Again, not really into the technical details. Just giving what my gut reaction says and hoping for an explanation.
9147877 In the original, it was Sol 549.
In this story, Hermes was two days later on its Earth fly-by, so it returns to Mars on Sol 551.
9147842 "The airport novel is the book this is a crossover with."
I know the airport novel is the book this is a crossover with, because I'm the person who referred to it as one. I don't think you understood what I said.
9147724
... and when they get to Schiaparelli the Ares IV MAV has tipped.
9147895
Since you said you didn't know what a pirate ninja was, or what airport novel he was cribbing from, I assumed you were unfamiliar with the source material.
Either way, no need to be a jerk about it.
9147902
I said "[I'm unfamiliar] with the airport novel you're cribbing from".
I guess it'd probably help if you knew cribbing meant copying, and airport novel means pulp fiction, it's a disparaging comment. Literally "I am unfamiliar with the source material, which is probably bad".
So you responded with "the source material is the source material", which is, uh, obvious.
9147873
Because Watt-hours are the standard for measuring electrical power storage capacity, and watts likewise the standard for consumption speed. "Watts" just means joules per second.
Joules are a more generic measurement of power, and amperes and volts don't measure power at all, rather they measure characteristics of electric current relative to time. Something analogous to volts and ampres might be the diameter of a water pipe versus the speed of flow.
So if you wanted to use amp output to measure how much power something stores you're going to need to also know it's voltage, and how long it can run before expiring, and then the resulting figure you'll get will be a number in watt-hours anyway.
9147873
Because of electrical math:
'VIRPIV' as I call it, or Ohm's and Watt's laws.
V=IR // P=IV
Where V is Volts, I is Current in Amps, R is Resistance in Ohms, and P is Power in Watts.
Everything he deals with? Electrical?
Also, kWH tends to be counter-intuitive to a lot of people because they're used to measures of Unit over time... or a division equation (miles/hour... Meters/second...etc) . kWh are a multiplication value. Or Kilowatts x Hours
So if my computer uses 800 watts...
800/1000 = 0.8 kW
...Multiplied by the number of hours using it, 24.
0.8*24 = 19.2 kWh
So, let's say Mark's equipment is running at 24 volts and he's drawing 3 amps (this is COMPLETELY random, mind you). Since we already have volts and amps, we can ignore Ohm's Law and jump straight to Watt's law. P = IV Watts = 3 x 24 = 72.
72 watts for say, 12 hours.
(72/1000) x 12 = 0.864 kWh.
Yeah, kWh is really annoying energy unit to understand. But it's the standard.
9147873
I think the point people are making is that kilowatt hours is the correct term here, they're just distinct and different from using the term "kilowatt" alone.
9147942
"So if my computer uses 800 watts...
800/1000 = 0.8 kW
...Multiplied by the number of hours using it, 24.
0.8*24 = 19.2 kWh"
To clarify, 0.8kW draw, 0.8kWh of power consumed in one hour, 19.2kWh consumed in a continuous 24 hour period.
It'll never stop tripping people up, probably because Watts already relate to time but differently. I guess it's better to say 1kWh than 3600000 joules.
Ideally what we need is a new electrical scientist man to explode himself, that way we can rename kWh after him and end the confusion.
9147920
No, that's exactly what I thought you meant. My point was if you don't like The Martian why are you reading the crossover? Also that it's not usually considered an airport novel.
And the second point still stands. Yeah it's a mistake, but you're being a jerk about it.
However, at this point I'm done. Do enjoy or, if you can't, at least complain more quietly.
9147948
Yeah, the unit is kWh.
And at the risk of teaching others who don't know in general what all these terms are, I can equate them to a garden hose for clarity's sake.
V, or Voltage, is 'pressure'. It's what drives the electrical current. Also known as electrical potential.
R or Resistance is exactly what it sounds like, it is the KINK in the garden hose. It slows the flow of electricity down, but builds pressure behind it.
I is current and is also as it sounds. It is the flow of electricity through your circuit. You cannot control current directly. You must leverage either the voltage, or the resistance to control how much current you have. Thus, Equation V = IR is often written as I = V/R. Or, how much pressure is trying to shove through the resistance. If V goes up, so does I. If R goes down, I goes up.
So as a little mental experiment, if R approaches zero while V remains the same, what happens to I?
Well, simple, I approaches infinity. And that is bad.
Why?
Well, if in the other equation, P=IV, where P is power in Watts... Well, another way to call that power is HEAT.
If HEAT = INFINITE CURRENT times VOLTAGE....
Heat = infinity times 1? ... Infinity Times ANYTHING?
HEAT... INFINITE!?
Congratulations, you've just discovered mathematically why a short circuit sets your wiring on FIRE.
9147873
Hm, aye, that too.
9147859
The converter may also lack the moving parts of a magic!motor-generator set, which seems like it'd be an advantage for a spacecraft. And, as you say, even if magic!motor-generators were known and had significantly higher efficiency that whatever converter the ship used, that doesn't matter so much when the fuel is plentifully omnipresent.
9147961
Yeah, I agree, the kWh unit is, as I said 'counter intuitive'. We're used to rates being in units over time, and the units themselves being discrete packets of whatever they're a value for.
The kWh is a bizarre term for a packet of energy because it's expressed more like a rate than a discrete unit. It makes it really hard to wrap your head around it and visualize the unit. With something like a Joule, I could visualize it like drops of water in a glass. 3,600,000 joules, or 3.6 megajoules is just 'a glass of water' in my visualization.
19.2 kWh is... I can't even visualize that in my mind. I try to visualize it, and I hear a buzz and see a glowing wire. I can't quantify it and come up with a discrete 'number of packets of energy' from it. The value doesn't 'connect' to anything finite because my brain keeps trying to see it as a 'rate'.
Hmmm... magic to electricity is inefficient, and yet—
— which leads me to hypothesize that converting magic to kinetic energy is WAY more efficient.
So my little monkey brain is wondering how long, how fast, and at what mana drain could Starlight spin one or more of the rover wheels when they're parked for the day. I seem to recall that an electric motor is basically a generator in reverse, after all.
https://www.youtube.com/watch?v=VGBB929PFKc
You want a list?
Yeah what could go wrong with feeding a magically created storm more magic?
9148120
somehow that made me think of "all bottled up": "i used magic so that i wouldn't use magic. i should have guessed that would backfire."
Seems NASA spoke a little too soon...
Just kilowatts here, the rest can be explained by people that have to say "kilowatt-hour" a lot often shortening it to "kilowatt".
Starlight, of course, possesses UN-LI-MI-TED POWER, but what he cares about here is energy per unit of magic, not power.
By launching another rock?
memegenerator.net/img/instances/73513462/do-it.jpg