Spaceflight is famously expensive. Each Saturn V used to put two men on the moon for a couple of days cost over a $100 million dollars per launch in modern dollars. Each launch of a Falcon 9 costs around $60 million to deliver about 10 tons to LEO, a per kg average price of $6,000 dollars. Yikes.
But, where does this cost come from?
An obvious answer would be the fuel. A rocket after all is mostly fuel. This however is not the case. In fact, if one only had to worry about fuel costs, spaceflight would be quite affordable.
Just how much fuel does it take to get someone into orbit anyways? Well, it of course depends on the fuel. Lets assume
a liquid hydrogen oxygen mix. This gets about the best performance available from purely chemical fuels, with about a 4 km/s exhaust velocity, using the space shuttles engines as a guide.
Getting into low earth orbit (LEO) requires about 10 km/s of delta v. Using the basic Tsiolkovskyrocket equation, this suggests hydrogen engines need a mass ratio of about 12. Or, for every 1 kg of cargo, you will need to expend 11 kgs of fuel. Outch.
Now, how does this translate into a ticket price? Well, lets assume each passenger requires about 200 kg of “cargo”, between the passenger, his luggage, and the weight of the spaceship itself. So per passenger, we will need to buy about 2.2 tons of rocket fuel. That's a lot of fuel!
However, that amount of fuel would only cost about a $1,000 dollars, with hydrogen fuel actually averaging out to about 50 cents per kg, with the Oxygen costing around 15 cents per kg, and the Hydrogen costing about $2.50, and one using about 4x as much liquid oxygen as liquid Hydrogen.
Now, a $1,000 dollars isn't nothing, but its absolutely tiny compared to current launch costs. This seems to suggest fuel costs, at least directly, are not a major driver of costs. This has been confirmed by those in the field. For example, Musk has stated his $60 million dollar Falcon 9 contains about $200,000 worth of fuel. Thus, fuel only represents about 0.3% of his launch costs.
So, where is the cost coming from then? The simplest answer is lack of re-usability. Modern airplanes and spacecraft seem to be roughly comparable in cost per mass. However, a modern plane will hopefully be used hundreds, if not thousands, of times over its life, while most spacecraft are only used once.
For example, lets take a theoretical passenger shuttle that can carry 100 people into LEO. Lets say the ship cost $100 million per ship. Now, what would the cost be, considering just the cost of the ship and our earlier $1,000 dollars per passenger fuel cost?
If the ship is used once, like most current launch vehicles, the ticket price would be $1,001,000. $1 million per passenger in ship costs, plus a $1,000 dollars in fuel. Or about $5,000 per kg. This is roughly in line with current launch costs.
What if the craft could be used 10 times, instead of once? The cost of building the spacecraft could be spread out across 10x as many passengers, and the ticket price could be reduced to a “mere” $101,000 per ticket, or a little over $500 dollars per kg.
Now, lets get really crazy and say this $100 million craft can be used a 1,000 times, say once a week for 20 years. This means the cost of the spacecraft's expense can be spread out over about 100,000 tickets, and the ticket price can fall to about $2,000. $1,000 for the spacecraft, $1,000 in fuel per passenger. Or about $10 dollars per kg in cargo.
Thus, if the other issues could be solved so fuel was one of the main driving factors of price, a ticket to orbit might cost not much more than a long distance flight to Australia. At least potentially. And like long distance flight, space travel would thus be the realm of the merely upper middle class, rather than the richest 1% of the 1%.
Is this at all realistic? Who knows. However, it does suggest how affordable a developed, established spaceflight could be, if the re-usability problems could be solved, a world where spaceflight is not much more difficult than flying to Australia is not nearly as far fetched as one may initially think.
But, where does this cost come from?
An obvious answer would be the fuel. A rocket after all is mostly fuel. This however is not the case. In fact, if one only had to worry about fuel costs, spaceflight would be quite affordable.
Just how much fuel does it take to get someone into orbit anyways? Well, it of course depends on the fuel. Lets assume
a liquid hydrogen oxygen mix. This gets about the best performance available from purely chemical fuels, with about a 4 km/s exhaust velocity, using the space shuttles engines as a guide.
Getting into low earth orbit (LEO) requires about 10 km/s of delta v. Using the basic Tsiolkovskyrocket equation, this suggests hydrogen engines need a mass ratio of about 12. Or, for every 1 kg of cargo, you will need to expend 11 kgs of fuel. Outch.
Now, how does this translate into a ticket price? Well, lets assume each passenger requires about 200 kg of “cargo”, between the passenger, his luggage, and the weight of the spaceship itself. So per passenger, we will need to buy about 2.2 tons of rocket fuel. That's a lot of fuel!
However, that amount of fuel would only cost about a $1,000 dollars, with hydrogen fuel actually averaging out to about 50 cents per kg, with the Oxygen costing around 15 cents per kg, and the Hydrogen costing about $2.50, and one using about 4x as much liquid oxygen as liquid Hydrogen.
Now, a $1,000 dollars isn't nothing, but its absolutely tiny compared to current launch costs. This seems to suggest fuel costs, at least directly, are not a major driver of costs. This has been confirmed by those in the field. For example, Musk has stated his $60 million dollar Falcon 9 contains about $200,000 worth of fuel. Thus, fuel only represents about 0.3% of his launch costs.
So, where is the cost coming from then? The simplest answer is lack of re-usability. Modern airplanes and spacecraft seem to be roughly comparable in cost per mass. However, a modern plane will hopefully be used hundreds, if not thousands, of times over its life, while most spacecraft are only used once.
For example, lets take a theoretical passenger shuttle that can carry 100 people into LEO. Lets say the ship cost $100 million per ship. Now, what would the cost be, considering just the cost of the ship and our earlier $1,000 dollars per passenger fuel cost?
If the ship is used once, like most current launch vehicles, the ticket price would be $1,001,000. $1 million per passenger in ship costs, plus a $1,000 dollars in fuel. Or about $5,000 per kg. This is roughly in line with current launch costs.
What if the craft could be used 10 times, instead of once? The cost of building the spacecraft could be spread out across 10x as many passengers, and the ticket price could be reduced to a “mere” $101,000 per ticket, or a little over $500 dollars per kg.
Now, lets get really crazy and say this $100 million craft can be used a 1,000 times, say once a week for 20 years. This means the cost of the spacecraft's expense can be spread out over about 100,000 tickets, and the ticket price can fall to about $2,000. $1,000 for the spacecraft, $1,000 in fuel per passenger. Or about $10 dollars per kg in cargo.
Thus, if the other issues could be solved so fuel was one of the main driving factors of price, a ticket to orbit might cost not much more than a long distance flight to Australia. At least potentially. And like long distance flight, space travel would thus be the realm of the merely upper middle class, rather than the richest 1% of the 1%.
Is this at all realistic? Who knows. However, it does suggest how affordable a developed, established spaceflight could be, if the re-usability problems could be solved, a world where spaceflight is not much more difficult than flying to Australia is not nearly as far fetched as one may initially think.
