The Fermi Paradox

The Fermi Paradox. For those unaware, the Fermi paradox is simply stated: Everything we know about life on other planets tells us that life should be commonplace across the stars and we should be able to see evidence of alien life. (Corollary, life should be common enough that we shouldn't have had time to develop before our planet is colonized) The problem comes that we don't have any real evidence that alien life exists. There are a few sightings that might indicate alien life, (Weird telescope sightings of other star systems that would theoretically indicate intelligent life, not the aliens in Roswell type) but they're slim and nebulous. Life should be everywhere, but we see none of it. Some sort of Great Filter stops life from being visible to us, or even existing. Therefore, the next step when talking about the Fermi paradox is to discuss why we don't see any signs of intelligent life.

Personally, I find that your reaction to this problem is the interesting bit. There's a whole host of possibilities for why our observations are different from our expectations, and little data to work on. Therefore, your thoughts on the cause are likely to be inspired by thoughts outside of this specific problem, which is why I find it fun. It's a science fiction Rorschach test, if you will.

I find it useful to split possible solutions to the paradox based on whether they come relatively after or before modern humanity. If the problem is before current times, then it likely means that humanity is special and has already passed the Great Filter. A bit of optimism is required, but also can indicate how you think humanity might be special. You could think that life is special, and exceedingly rare enough that only Earth is lucky enough for it. Maybe you see intelligence as unique, after all, life existed for some 3.6 billion years before humans came around. Maybe even it's something unique to humans where complicated industry to become spacefaring is out of reach? We did spend a long time planet-bound, and extinction level events aren't unheard of.

Problems that the future of mankind will have to deal with are often depressing and pessimistic. Maybe we'll beat them, but the evidence we see amongst the stars tells us that the odds are very much against us. What we know gives us a rough guess of just how many other civilizations have grown and likely run into the very same problems we'll encounter. Maybe you're optimistic that we'll beat the odds anyway, but good luck with that.

What kind of problems are we talking about for the future? There's the ever popular nuclear armageddon where nuclear weapons are developed, and inevitably used to end life on that planet. More popular during the Cold War though, given the circumstances. Perhaps some early idiot made self-replicating robots that kill any species that makes it into space. All it takes is one idiot species. Perhaps we run into societal traps. Is there any real point to colonizing other planets? Much simpler to keep humanity limited in scope so that we can all live comfortably on Earth. Or even better, live in a simulated dream world. No need to expand all that much if everyone only exist as programs in a machine.

There are plenty of other problems that could be a potential killer for spacefaring life. This is by no means an exhaustive list; I'd be here all day listing them if it was. For those that do read this...what do you think is the cause?

Game Combat Basics

I find myself building a small thing with combat as a creative exercise. It's not something I'd ever want to share, especially on here, but talking a little bit about specifics helps. If nothing else, writing about it helps clarify things for me, so even if no one reads this, I've still benefited from it.

Let's start with the basics. The goto basic combat system is the Dungeons and Dragons combat system, specifically version 3.5. Why? It's basic, understandable, and easy to calculate. You don't want to use a calculator for tabletop gaming, nor do you want too many numbers in the way. It works like this: Roll a d20 (a die with 20 sides, with values 1-20) and add your attack value. If this sum is greater than your opponent's defense, you hit and then deal with damage. Simple, straightforward, and easy to implement. So you drop it into your game, try it out, and find that it isn't a very good system at all for a computer game.

There's a few reasons it doesn't work well in a computer game. Chief among them is that DnD is designed around rolling dice. Rolling a die and seeing the result is an intrinsically fun action. Having a computer roll the dice for you and it's not nearly as fun. Whereas in a DnD setting you'd watch that die bounce and either come up short and succeed for you, all you see on the computer is your character whiffing or hitting, and if you're using values like those found in DnD, he'll be doing a lot of whiffing. Now you're wasting time watching the computer duke it out with itself as both parties whiff ~40% of the time. What fun.

There's other issues too, mostly relating to how offense versus defense scales. The main defense in this system has you avoiding full damage more often. Specifically, each point of defense makes you 5% less likely to be hit. Each point of attack increases your chance to hit by 5%, effectively cancelling out a point of defense. Which means if your attack scales at the same rate your opponent's defense scales, nothing will change in this system, even as both of you get stronger and stronger. Actual damage dealt and maximum health might scale as well, but the fight still looks similar. There's also issues when attack and defense values vary widely from each other. What happens if you have 100% chance to hit? 0% to hit? Could I reasonably make a monster that still stands a chance if it only hits 5% of the time? If you hit most of the time anyway, why still have this system?

(Note: DnD also has the suggested house rule that a natural 1 always misses and a natural 20 always hits. Setting a minimum and a maximum like that certainly works as a solution, but is not necessarily a solution that solves the problem)

This system as a basis for making things work doesn't do well in a computer game setting. Luckily, there are other alternatives. Instead of hitting or missing, we can take that out entirely and have defenses reduce damage. Again, we keep things simple and deduct our armor amount from any damage we take. 10 damage against 5 armor means that 5 real damage is dealt. This system works, but runs into other funky problems. Most notably that damage taken depends heavily on how much damage the opponent does per shot relative to the amount of armor. If the rate of attack can vary, slower attacks will be much stronger relative to smaller but quicker attacks. Designing a proper fight from the developer's perspective can be odd too.

Say I wanted to double the damage taken from my last example. I can't double the original damage, that'd result in the target taking triple damage instead of double. (20-5=15 or 5x3) Instead, I want to add 5 damage. As well, I need to keep damage relatively similar to armor levels. High damage makes small amounts of armor relatively useless. If I'm taking 30 damage already, would 2 more armor really help? The reverse is also problematic. Going back to the original problem, if I add 2 armor there, I'm only taking 3 damage a shot, or a 40% reduction.

All that may not be a problem though. If I have numbers setup right, things should (repeat, should) work fine. It's still a funky system though, and I might prefer some flexibility. Next attempt is percentage damage reduction. It works regardless of rate of attack, works on any number equally well, and dealing with relative increases of power are straightforward. Of course, it has its own issues.

First, it's more complex than the others. I don't need to worry about computational complexity because the computer will handle it, but I do need to worry that the player understands how much his shiny new piece of armor actually helps. I also need to get the math right. Two pieces of armor, each with 10% damage reduction, should not add up to 20% damage reduction. If they do, that means that later pieces of armor are much more valuable than they appear, and lead to silliness. Using terms like "10% damage reduction" also look silly; ideally I'd like to have a term like "armor" that turns into damage reduction after the fact, for which I'll need to tell the player somehow. Or not, and leave it to the wiki.

There's the other problem of small numbers. If I deal 10 damage, anything less than 10% damage reduction doesn't do anything, because it'd reduce by less than 1. I can keep the number as a decimal, but that looks strange if I'm using small numbers in the first place. (And leads to one of the few legitimate times where 2+2=5) It can also seem worse than it is. The rules I originally used had attack and defense values change in increments of 5%. If I'm at 50% damage reduction, an additional 5% damage reduction would reduce damage by 5%, but it'd look like it's only doing 2.5% (assuming I tell the player the total damage reduction from armor) If you don't know math, it then looks like armor gets worse and worse the more you get, even though that's far from the case.

Maybe I'll do another post sometime looking at other problems or issues. Maybe not. If you have any questions, especially about the math in this, please be sure to leave a comment and I'll get back to you.

Alien Domesticated Animals

Today, I want to think about aliens. Not the usual aliens that think and act and somehow look like humans with funny foreheads, but the dumb ones. I'm talking about the domesticated kind. What would aliens look for in domesticated animals? Preferably, what would they look for that isn't almost exactly the same as what we have on Earth? Something alien, not a space dog, yet still similar. Why am I talking about this? Because I can. And because I watched this video from CGP Grey:

(If you watched, go watch! It's a good video)

Which got me thinking: "What traits might we want from an animal, if we could imagine animals as drastically different from what we have now. What might an alien want that is very different from a human?" So lets start with something easy. Everything living needs energy to survive and be active, so it's a reasonable assumption that sentient aliens would need to eat. (Except maybe those fancy green aliens that cheat). While it's true that turning grass into meat is inefficient calorie-wise, it's pretty useful if the grass is useless to us anyway. Some calories is better than none. It's also a big bonus if you get a taste boost in the bargain.

When we look at the chemical factories we call digestive systems in Animals on Earth, we see that specialization is key. More specialization in what we eat means more efficiency. You don't need to worry about specialization when your diet consists of calorie-rich fruit, meat, and vegetables like the diet humans tended to have. Yet, if you want to eat food like grass that is minimal in effective calories, specialization is the only hope. Rather than go through the hassle to turn grass into edible material, easier to have an animal already suited for the job do it for us. Other examples of inedible food include poisonous plants, food waste, and carrion. Perhaps we're looking purely for taste, ala honey (or aphids for ants).

I'd think it a no-brainer that aliens would have some form of domesticated animal that turned inedible food into something edible. The fun part is in imagining how the alien gets the calories from the animal after. On Earth, it's most efficient for animals to produce food continuously, rather than only slaughtering them once they've grown. The big two examples are milk and eggs. Making meat is expensive, it requires the animal spend calories to make the cells, then those cells must be maintained requiring more energy the longer the cell lives before butchering. Comparably, milk and eggs are a single energy expenditure, no energy maintenance required.

Maybe we find an animal that can compromise. Lizards are an animal that can continuously regrow lost limbs, with some even using it as a defense mechanism. Why not a domesticated animal that can consistently grow meat without needing to be butchered? Or get really alien. Have the male be an omnivore similar to humans, while the female has a diet more similar to a horse or perhaps cow. (Or reverse the roles, if that's your preference) Even better if they have some foods to share that both enjoy, such as high-sugar foods like honey. What would society be like if men and women didn't ever share meals, but had the occasional dessert together?

As well as making useful calories, animals produce other useful materials. Bone, fur, feathers, wool, ivory, leather, silk; there's a lot of useful materials we derive from animals, especially before more advanced methods of production are found. We've only recently (relatively) developed alternatives to some of these items that don't require animals to produce. I'd find it incredibly likely that alien civilizations would use animal products as well, in likely similar uses as in our past. Building materials, decoration, and especially temperature regulation are all too good to pass up. Always a great choice in a story when you need a material made is to have it be made by an animal. Which seems sillyat first, but considering that guano (aka bird/bat poop) can be easily refined to become the main ingredient in gunpowder, using animals as chemical factories doesn't seem so odd.

The last major usage for domesticated animals is as workers. Preferably, they have other purposes from those listed above to be as efficient as possible. The horse is the best example. It can be used to carry things we'd rather not carry, including us. It runs at high speeds, faster than we can. Even better, it runs off of food we don't eat, and can convert it to food we can eat. Milk and meat even. Other examples are great: oxen for heavy lifting, cats for killing vermin, dogs for herding and their enhanced senses, and others. Effectively, anything your alien can't do is good grounds for employment of animals, along with anything a sentient doesn't want to do but still needs doing. Humans can certainly pull along wagons, but the oxen whine less. Dogs have different senses than us, making them highly useful for compensating to obtain a fuller range of senses. Presumably, an alien that lacks in good eyesight could have a more literal seeing eye dog as a companion.

Effectively, if you ever find yourself imagining an alien species, try to look too at what domesticated animals they're likely to have. Look for holes in their biology, then think of ways other animals could help fill those holes. Don't forget to add some variation to the animals too. Most farm animals are pretty docile, but horses have an attitude and camels are jerks. Don't horse around by making the animal the same as a cow, except In Space! Unless of course, you're making a joke about how aliens seem to like our cows so much. Please remember to milk that joke as much as possible. Hope you enjoyed the read, it's time for me to get mooving to another project.

How to Sell a Video Game Part 2

(Here's part one if you missed it: http://seacdev.blogspot.com/2016/02/how-to-sell-video-game.html)

Last post was all about the difference between variable and static pricing. As you'll recall, variable pricing is where the producer sells the same (or mostly the same) product to consumers at different prices. When talking about the videogame industry specifically, the big advantage from such a practice is being able to treat your customers as a group, instead of single customers. As long as the average sale price for each customer is high enough, the producer can make his profit, even if some people don't pay a cent.

What's the advantage to treating customers as a group instead of solo purchasers? While also utilizing the traditional advantages to variable pricing, it makes great use of social connections. Put simply, people like to play with their friends and to look good to other people. Take two friends that want to play a game together. Because they will only play together, there's no sense to treat them as two separate customers. Instead, it's better to treat them as one single customer.

Before the internet was a real thing for gaming, their options for a single purchase would mostly be console games, often using split-screen or having everyone on the same screen. One game, one purchase, but multiple people playing at the same time. As far as PC games go, outside of illegal activity or the rare two players on one monitor game, the only company I know of that had anything similar that I know of was Blizzard games and their spawning mechanic. Same idea applied though. Best example for a game targeted at a group instead of a single player was Rock Band/Guitar Hero. The game plus peripherals was expensive, but the combined experience was a lot of fun, and with the purchase split across the group the cost was very similar to other games.

Now with the internet, producers have more options to sell to customers and still target them as a group. Broadly speaking, I'd split the methods into three major groups (though possible overlap is always available): ads, cosmetics, and power. As well, all the old traditional possibilities are still available, but have the possibility of being smaller. A producer can sell a content expansion same as before, but only sell, say, $5 worth of content while getting the same percentage of profit as with the old $30 expansion. The old practices didn't disappear, but instead get smaller and more targeted.

Ads are simple to explain, just about everyone is familiar with them, because it's been the sales method of choice for public entertainment for decades. TV doesn't ask you to buy an episode before you watch it, opting to show ads along with the show to generate their revenue. Doing it with games works in a similar manner. The interesting bit with this method is there's no decision needed in order to "purchase" the content.

Seems small, but think of how much you care about a small decision to buy a $2 coffee. It's only $2 right? How hard can the decision be? Surprisingly, it is a difficult decision to make. All money is precious, even small amounts, and for most people a small amount of money still requires the thought any other purchase will take. The small amount of money actually ends up working against the producer, because rather than go through the decision making process on the worth of a game, it's often easier and better to skip the process entirely. It's only $2, it couldn't be worth that much to you to have you go through the decision making process. Hence, the big advantage to selling via ads, is you can skip that process entirely. Usually, it's made better by offering the option to skip ads entirely, for those that want to make that decision. Again, more options to sell to customers is better.

For me and my game, the plan is to sell via ads with the option to disable them for a price. I don't expect to make a game that's worth all that much, so I imagine the "worth" of the game would only be ~$1-$3. I could sell it straight for what it's worth, but given how unknown both me and the product are, I wouldn't expect to get many people past that decision threshold, even if they would deem my game worth the time if they had the chance. Why not sell cosmetics or power as well? Short answer: a singleplayer game like mine doesn't have enough social connection to make cosmetics valuable, and the game isn't setup right to take advantage of selling power while not annoying legitimate players.

If people really want to hear more analysis about selling cosmetics and power in games, feel free to let me know and I could do another post about them. Until then, I think this mostly answers the question of my choice of sales decision.

Final note: Please, if you found this interesting, make sure to like, share, and subscribe. They're really small actions, but it's surprising the effect they have on spreading projects around. Thank you, and hope you enjoyed reading this.

How to sell a Video Game

As some of you may have heard, I'm currently working on producing a little Android game with a friend. The interesting bit is whenever I talk about the game, there's two questions that are almost always asked: "What's it about?" and "How are you selling it?". The first is quick and easy: It's a little town building game. The second, while also quick to answer, is interesting because it is being asked. Not too long ago, if one were selling a game, it'd be sold the same way every other game would be sold. Now, things are a bit different.

Games are traditionally sold like any other product. A producer constructs a game, a store buys the game from the producer, and the store sells the game to a customer. One price for everyone, barring the occasional sale and markdowns due to age of the product. Additional content to a game, such as a new campaign or a map pack, would be sold similarly. This made a lot of sense for the time, especially as a substantial portion of any game's price was tied up in the physical bit of the game. Cartridges weren't cheap, especially later on as they were used to add additional capabilities to the consoles. Now, I can download a game for maybe pennies. Development time is expensive, not the actual content itself.

Importantly, I think it should be said that selling to customers should be a 2-way deal. Both sides should be happy, and a good sales strategy should take that into account. Only a few are really built around "exploiting" customers, with the other strategies being variations on the same principle: get the best product to the customers at a reasonable cost. A developer needs some way to get money if he wants to produce content. Finding a better way to gather that money allows him to make more content for those same customers to consume and gain a better life.

Moving back to how games are sold, even though the traditional market still functions traditionally in many respects, some new aspects have crept in. Most especially, smaller direct transactions have entered the market. Often termed "microtransactions" or "DLC" (downloadable content), these come in many different shapes and sizes and have fundamentally changed how game markets. Sometimes, some games have even completely eschewed the traditional market structures in favor of newer models. On the mobile market, at least for Android, you've seen the traditional market disappear entirely.

So, why the interest in these new models? In large part, they're done to cut out the middleman and allow for variable pricing. Any given store will usually take a good chunk of any sale for their cut. Steam takes about 30% of any sale for themselves, and last I knew sales in a more traditional store would take more. Not having to pay that bit is huge, especially give that modern software for handling money transactions safely is fairly cheap in comparison.

Explaining variable pricing is more complex, though it is covered in any basic economics course. Essentially, the idea is that game producers have a monopoly on the sale of their game, and so can charge any price that they choose. The cost to produce each individual item sets a general floor for the cost, but given it costs pennies to actually sell, the developer can ignore that, and so only cares about the demand curve. A demand curve is simple, for any given price of the product, you can expect some number of sales.


Here's an example. Say we know for certain that this graph is accurate. What price do you sell your game at? If you only have one price available, you look at where the price x items sold creates the biggest value. Here, that's the $20 mark, where you'd make $4,000. Great huh? But there's a better way. What happens if we sell to everyone at the $30 mark, and sell to everyone else at the $20 mark? You'd make $5,000 instead. That's a good amount more money, through no change in product. The trick, then, is how to actually make the sale such that some customers pay more than others.

Traditionally for many types of products, the common ways to do this are through sales and brands. Some people will pay extra for a brand name, while others don't care and will buy the same, unmarked product. Sales are another, where savvy customers wait for the right time to buy, while others don't care and pay extra. Both work, and are used to some extent in video gaming, but there are better ways, some exclusive to gaming.

These methods, I'm sorry to say, will have to be explained in an other post. As always, if you have questions or comments, please make sure to leave them and I will get back to you. I hope you enjoyed this bit, and make sure to check out my youtube channel at  https://www.youtube.com/channel/UCNf-NV3nO5CM0BXFAyZJc5Q

Kerbal Space Program AAR, The New Plan

Remember how I had said that we had enough money to finally upgrade the construction facility? That was only technically true (the best kind of true though). While we had the money to upgrade it, we lacked the money to get any use out of the new upgrade. A sad state of affairs for us, as we wouldn't be going anywhere new this time, but ah well. Earning one's worth never hurt. The selection of contracts is interesting though, and I pick out a few.

First up is another mission to save the hapless pilot of a careless private space program. Good pay, better than usual even, so what's the catch? They forwarded the details over, and it became apparent what the catch was:

Looks like they had intended on going for a Munar runby. All seemed well until on the return trip back they didn't have the fuel to re-enter the atmosphere. Normally, I'd put this up to bad rocket craftsmanship, but looking closely at the data, I realized that they had gone west instead of east.  They didn't want it known publicly that their flight plan was completely backwards.

 I wanted to go blabbing to the press at yet another failure by the private industry in the hopes of getting more contract money sent our way, but Fishman had me promise not to. Signing the contract meant we'd be stuck to silence. What I wouldn't give for the chance to send all lawyers into the sun.

Well, no time for that now. I have work to do in getting that pilot back home. I had plenty of time though, as she's a day out from a good intercept point. Rather than wasting the entire day, I have Capt. Kiwi suit up for a side mission. As well, I grabbed two other missions, one to test parts, along with a future run to Minmus. Likely we'd do it after rescuing the lost pilot, but for now the juicy advance money would come in handy.

It was the usual Aeronautics mission. Go take temperature readings somewhere in low altitude. Easy money. This one was a short flight over, just past the lower peninsula I named "Kerbea".

Capt. Kiwi and his trust flyer were soon brought out onto the runway. Easy money.

The beauty of these trips is great. We don't normally get such good pictures from our rockets. Something about too much wind pressure breaking the cameras.

Almost half an hour later, and Capt. Kiwi begins approaching the Kerbean peninsula. This marks the halfway point to his mission objective.

Another 20 minutes later and Kiwi was "busy" collecting the readings. Simple job really. I'm not sure why they wanted readings over empty water like this. Isn't the weather over land where all the interesting stuff happens? You can barely see any from here, even 11,000 m above water.

The collection goes smoothly, and Capt. Kiwi moves to begin landing. He cuts power to the engines, and dives down; he's eager to get back home. Something something religious celebration.

I warn him about the treacherous water, but he insists. It'll be fine, he says. If the plane lands on hard ground, why couldn't it handle a soft wet landing?

Final approach, he's slowed down as much as he can. Splashdown imminent.

Why doesn't anyone listen to me? Kiwi's craft hits the water with enough force to rupture the tanks. launching him up into the air again and destroying much of the craft. Luckily for him, we heavily reinforce our crew compartments.

He lands safely a short distance away. It cost us some money in damaged parts, but maybe we'll get it back in advertising money. The people do love a good explosion, especially if it is because of someone's silly decision.

Kerbal Space Program AAR, Ship Design Explanation

While working on the plans for the next mission (which would be a doozy) Wixit the engineer came to me with a straightforward question: "How do you design rockets?" Given his ample time at base with not much else to do after his promotion, he had had plenty of time to study up on actual engineering. I was certainly busy, but my interest in getting work done was competing heavily with my interest in talking. I do so love to talk.

Ah, what the hell. Missing a bit of work wouldn't hurt anyone. We would be waiting a day for that rescue attempt anyway. I pulled out my charts and sat him down. Class was in session.

The first important bit of information involves explaining the interface. In the bottom right we have our current mass and size values and their limits, along with any warnings we might have. The limits are based off of our infrastructure. Size and mass were dependent on our launch pad, while the number of parts is based off of the construction facility. Always make sure to take these numbers into account when designing your craft.

On the left hand side we have our parts list. Parts are separated by function. Additionally, the parts greyed out require an additional purchase cost for us to use. In the center is the craft we're currently constructing. On the bottom left is the cost of the rocket so far, along with buttons for center of lift, center of mass, and center of thrust. There is also a button for where objects are placed along the edges, and if you want more than one of the same object to be placed symmetrically around the area.

That explained, the next part is to figure out the design of your rocket. First step is to determine your mission: the reason for the craft to exist, sans any concern about actual rocket equipment. For this example, lets say our mission is a trip into low Munar orbit, carrying along Science! equipment and a full Kerbonaut group. Put that together, optimally placing everything within the rocket, rather than on the sides so as to reduce drag and worry about it burning off. Make sure to place the sturdiest piece of equipment on the bottom.

Next, put up any extra considerations that aren't "Rocket"such as batteries and communications. If we want communications, we'll need batteries to fuel them, so we add some of both as well. Keep in mind that the command pod comes with a small amount of energy storage and uses some energy to move the ship. Unless you add solar panels, the only way to get more energy is to run the liquid-fuel rockets. Don't run out of energy.

The next step involves noting down and adding up the dV requirements of your mission. If you're unsure of what I mean by dV and other rocket considerations, I've written up an explanation before on this matter here. This step does involve calculations, although you can often just wing it if you're familiar with the values.You can also calculate your own values, but handy guides like this map are always nice to use. It's easiest to start from the last one and work your way up. Add on an extra percentage for mishaps and pilot errors. 10-20% for most should be fine. Don't add on trips that we'll use aerobraking for, like the last leg back to Kerbin.

Chart from the linked page

Using our chart, we're going to low Munar orbit and back, so that means our order goes (Counting backwards remember): 3400 (aerobraked), 860, 310  (cut both in half because we're only getting into a very ellipical orbit), 310, 860 (partially aerobraked), 3400 (We can roughly split this into 1400 m/s atmosphere and 2000 m/s orbit). Add them up for our total dV needed, along with the extra dV for pilot error, and we get 5,400 m/s of dV needed.

The next step is to decide where the stages go. Good times to split are when you have a lot of unneeded mass hanging on, or when conditions change and you want different engines. In our case, our rocket has three good stage points. Kerbal ground to Kerbal orbital height is a good one, because of massive changes in conditions. We don't have to worry about atmosphere, nor is thrust such a concern by that point, so it makes sense to ditch part of the craft there. The second good timing is on the last leg, where we're aerobraking down to Kerbal. We don't want to drag the leftover rocket section, because we can't properly shield it. Depending on the specific parts available to you, splitting up that middle section into two could probably be a good idea, but we can't because we're limited to 30 parts in our craft.

Now that we have our requirements, we work our way down and fill in the rockets. We start with our last stage, which contains the mission payload and which only aerobrakes. Aerobraking is straightforward for us, we just add a heat shield, along with a parachute for the last leg of the journey so we can land safely. There are various calculations you can do to make sure we have enough heat shield and parachutes for the trip down, but we'll skip those for this. Finally, add on a explosive to start the stage onto the bottom, and we have our last stage done. Mark the mass of this stage.

We move on to the next stage. This one has a rocket portion, so we want to select the engine for our tasks and add enough fuel. When choosing an engine, look for three things: Thrust, Isp, and size. We want an engine that's the right size for the rest of our rocket. Too big and we're wasting fuel lifting  up the mass of the engine. Too small means not enough thrust, which is bad. We need enough thrust to do the job, which will vary on the job we're doing. For this stage, we're limited by getting into orbit quick enough before we fall back down, so we do want some thrust, but we're mostly concerned about the Isp.

For now, we'll use this engine. It has good Isp, though not great, along with good thrust. It should work fine for our purposes. Next we add fuel, of which we need approximately 3,800 m/s worth of it. What we're looking to calculate is the mass ratio of our rocket, basically (mass of the rocket when full) / (mass of the rocket when empty of fuel). We find our required mass ratio by doing e^(dV/(Isp*9.81). Plugging in our numbers gets a result of ~3.3. ~30.3% of our mass is rocket, the rest is fuel. Assuming we have weightless fuel tanks, we'd need 9.7t of fuel. Sadly, they are not, and so we need 1/8th of our fuel mass in fuel tank mass. Effectively, we come out to needing 1.75 more tons of tank mass, giving us 14t of fuel, and requiring 13.7t of fuel. We've got only a bit of fuel remaining for additional pilot mishaps beyond the projected 10%.

Our final stage requires only ~1,540m/s of fuel, though it is in atmosphere where rockets tend to perform less well than in a vacuum. Additionally, we want to worry about thrust a lot in this section. Ideally, when you're in a thick atmosphere like that found on Kerbin's surface, you want about 2 g's of acceleration. More than that and your wasting fuel fighting air resistance. Less than that and you're wasting fuel fighting the planet's gravity. When you're looking for high thrust and big parts, your best bet is always the solid-fuel rocket boosters. Here's the one we'll use:

We calculate our mass ratio again, but this time using the atmosphere value, and come to a mass ratio of ~2.5. Four of these boosters should do the trick, but we'll add a fourth on just in case. Our rocket isn't as aerodynamic as I'd like, and it's always good to have extra fuel if we need it. Don't forget to make every part as aerodynamic as possible. Small rounded caps on the tops of our engines are quite literally worth their weight in black gold.

This leaves us with our first stage massing in at 38.3t. Even though it has relatively little dV in it, carrying the rest of the rocket is hard work.

Now, what you should do Wixit is evaluate different scenarios. See what happens when you have missions that require more dV. See what happens when you add stages, and see where the breakpoint is between having more stages compared to fewer. What would a single stage rocket to the Mun look like?

I've got to get back to work. Enjoy your homework. Those contracts won't finish themselves.