Everyone Knows™ that putting stuff into space is expensive. Then Everyone Assumes™ that it's because of all the fuel. But no, fuel is cheap, hardware is what's expensive. If you look at the costs involved in putting something into orbit, the cost of fuel is a trivial detail, on the order of 1% of the total costs. Compare that to an airliner, where fuel is around 1/3rd of the total costs, or a car, where fuel can easily be over 50% of the total costs.
I happened to be reading up on rocket efficiency and I was surprised to learn that rockets are fairly efficient for launching stuff into orbit. Wikipedia uses the example of the Space Shuttle, where 16% of the energy in the propellants ends up in the kinetic and potential energy of the orbiter. That's pretty good!
The problem is that you use a rocket once and then throw it away. Imagine if your car was one-time-use. How often would you drive somewhere? How often would anyone drive anywhere? It wouldn't matter how efficient they are and it wouldn't matter if they didn't even require fuel at all.
Now, the rocket equation still comes into play here, because it means you need a lot of rocket for a little bit of payload. But the main problem is the one-time-use thing. A nuclear disposable rocket wouldn't improve things much. A reusable nuclear rocket would be great, but then so would a reusable chemical rocket.
This is the genius of SpaceX. For decades, rocket designers have looked at the rocket equation and tried their hardest to save fuel. SpaceX looked at the economics of rocketry and realized that fuel costs more or less don't matter, and instead concentrated on building their machines cheaply, and on making them reusable. We'll see how it works out, but if they succeed in making reusable rockets then they'll cut the cost of launches by an order of magnitude or more.
People have been trying to make reusable rockets since the beginning. The problem is that a reusable rocket is more complex, what means it's heavier, and that it needs much more fuel to launch, thus a bigger rocket, and the rocket equation makes everything astronomical.
Like everybody else, I cheering for SpaceX to solve this problem, but the challenge is not making a reusable rocket - it's making a light enough reusable rocket.
I'm not so sure. The Space Shuttle had a pretty big payload capacity. It had a lot of problems as well, but those were mostly due to being underfunded and hit with weird requirements beyond simple reusability. And that's really the only serious attempt at reusability that got beyond the early stages. It's still a pretty unknown area at this point, but I don't think building stuff sufficiently lightweight is necessarily the challenge. SpaceX doesn't seem to think it is, anyway. Their engines are not particularly high performance (meaning they need more fuel for the same job) and their rockets are engineered more for cost effectiveness than light weight. They seem to be making great strides precisely because they're not concentrating on weight. For example, their first stage reuse system involves carrying a bunch of extra fuel, where virtually every other attempt at reusability involved some sort of unpowered or nearly-unpowered landing after expending all fuel on the launch phase.
It blows my mind that SpaceX’s would think that “fuel costs don’t matter” given that the company is run by Elon Musk, who when he’s not doing SpaceX is running Tesla and being Chairman of SolarCity where fuel costs, in particular the environmental fuel costs, are basically the only thing that matter. It takes the equivalent of 25,000 gallons of gas to put a 200 lb person into orbit on a SpaceX rocket (yes, I know it’s not necessarily gasoline, but other fuels that are also either fossil fuels or create from burning fossil fuels). So a person would have to drive a Tesla for 120 years to save enough fuel for one spot on a SpaceX launch into orbit. Do environmental fuel costs only matter when you can save a few gallons on a two hour car trip, but not when you use 25,000 gallons for a two our jaunt into space and back?
Constructing machinery has huge environmental costs as well. The CO2 emitted in the construction of a car rivals that emitted by driving it afterwards, for example.
Getting into orbit requires a huge amount of energy. That's just physics, and there's no way around it. Spending lots of money on extremely complicated and efficient machinery to use less fuel getting to orbit does not mean you're more environmentally friendly.
Also, numbers matter. The environmental costs of space travel are completely insignificant, while cars are choking the planet, simply because there are billions of them. A tiny efficiency improvement applied to billions of cars will dwarf a gigantic efficiency improvement applied to a few rocket launches per year.
Good point about billions of cars having more impact than a few fuel-hoggy rocket launches.
I just hope that space-tourism doesn't catch on, because while you're correct that overproducing rockets to make them slightly more efficient does not make you more environmentally friendly, burning 25,000 gallons for a couple of recreational hours off the planet just because you have way too much money does make you an environmental monster.
Could be, but on the other hand it's also going to be much more complicated, which hurts reusability a lot. And you don't get nearly as much energy out of the nuclear fuel as you'd like, so the mass fraction isn't really that great.
Fuel is indeed cheap (The Russkies are using kerosene and liquid oxygen---you can source those locally yourself.), but hardware isn't expensive, either. The expensive part is designing hardware that works correctly, given that it is 90% fuel.
If a car was a one-time-use vehicle, it would be much, much cheaper than it is now, when it's designed to last at least through the end of the warranty period. Likewise, the Space Shuttle was reusable, but that reusability never actually turned into a win.[2] (I have a rocket-scientist friend who might convincingly argue that putting the Space Shuttle's budget into building a Saturn V assembly line would have been a net win. Building the same rocket over and over seems to have worked for the Russians.)
There are two downsides to reusability, particularly for man-rated rockets: How do you land, and what do you have to do to turn it around.
As was pointed out in the article, IIRC, the Shuttle could put 120 tons into orbit, but 100 tons of that was coming back down with the re-entry vehicle. Kind of reduces the effective payload. I don't know the details of the SpaceX reusability design, but I'm wondering where the landing fuel comes from; if it rides the rocket the whole time, it's coming out of the 10%.
The turn-around part is bad, too. Take a look at [1] for the Shuttle. The interesting parts are:
* "Transfer engines to the Main Engine Processing
Facility and service for future flights," and "When required, the orbital maneuvering system
(OMS)/reaction control system (RCS) pods and forward
RCS may be removed and taken to the Hypergol Maintenance Facility in KSC’s industrial area for maintenance." Yes, SOP involves major disassembly every time.
* "Visual inspections are made of the orbiter’s thermal
protection system, selected structural elements, landing
gear, and other systems to determine if they sustained any
damage during the mission. Any damage to the thermal
protection system must be repaired before the next mission." If!? I don't know the numbers, but after every flight, every tile was checked and a goodly number needed replacement. (They're not cheap, either.)
Is SpaceX flying man-rated yet?
Anyway, turn-around costs and not caring about re-entry make for a bit of cheapitude, too.
The Russians put stuff into orbit relatively cheaply, but not by a huge margin. Building the same rocket over and over again has worked out OK for them, but it hasn't dramatically reduced the cost of access to space.
The landing fuel for SpaceX's design is the same fuel as used to launch. A reusable Falcon 9 launch will have 30% less payload capacity than an expendable one, because of the need to save fuel for the landing. But the cost savings will be vastly more than 30%. So overall it's a big net win.
SpaceX isn't man-rated yet. They don't yet have a spacecraft that can carry people, so there's no point. That's being worked on, of course. The Dragon 2 spacecraft that will carry people includes a launch escape system, so it will be much more tolerant of launch mishaps than the Shuttle was, where the options for surviving a serious failure on launch were pretty much just "pray."
Turnaround costs and reentry shielding actually illustrate just how different SpaceX's approach is from the Shuttle's. They're only reusing the first stage for now. That means that there's no real need for a thermal protection system, so no worries with tiles. The engines are stressed a lot less, so they break less. The engines are also much less efficient (which is to say much less fragile) than the Shuttle's, and should need no refurbishment for subsequent launches. They're looking at reusing the capsules as well, but the heat shielding on those is tiny compared to what a Shuttle needed. They're not currently looking to reuse the second stage at all, but of course the rocket equation tells us that reusing the first stage is a much bigger deal. Just reusing the first stage gets you 90% of the cost savings of reusing everything.
The Russians put stuff into orbit relatively cheaply, but not by a huge margin. Building the same rocket over and over again has worked out OK for them, but it hasn't dramatically reduced the cost of access to space.
Buran, the USSR's shuttle, was a reasonably good idea. Although it looked like the US shuttle, it was really a vehicle carried on a big booster; it had no main engines. It flew once, successfully, unmanned. The Boeing X-37 unmanned mini-shuttle is similar, and seems to work well. The USAF keeps sending one up, keeping it up for a year, and then bringing it down to land on a runway.
The Buran is really interesting. It's a pity it never got enough love. I'm not hugely familiar with it, but it does seem superficially like a better approach than the Shuttle.
I happened to be reading up on rocket efficiency and I was surprised to learn that rockets are fairly efficient for launching stuff into orbit. Wikipedia uses the example of the Space Shuttle, where 16% of the energy in the propellants ends up in the kinetic and potential energy of the orbiter. That's pretty good!
The problem is that you use a rocket once and then throw it away. Imagine if your car was one-time-use. How often would you drive somewhere? How often would anyone drive anywhere? It wouldn't matter how efficient they are and it wouldn't matter if they didn't even require fuel at all.
Now, the rocket equation still comes into play here, because it means you need a lot of rocket for a little bit of payload. But the main problem is the one-time-use thing. A nuclear disposable rocket wouldn't improve things much. A reusable nuclear rocket would be great, but then so would a reusable chemical rocket.
This is the genius of SpaceX. For decades, rocket designers have looked at the rocket equation and tried their hardest to save fuel. SpaceX looked at the economics of rocketry and realized that fuel costs more or less don't matter, and instead concentrated on building their machines cheaply, and on making them reusable. We'll see how it works out, but if they succeed in making reusable rockets then they'll cut the cost of launches by an order of magnitude or more.