Spec Tech: Heavy Lift
There was an interesting bit of space news that came out the other day. The US rocket company SpaceX announced that they were going to push forward with their plans for a heavy lift rocket. As a rocket scientist and a big space fan this pretty big news. Not so much because the rocket—Falcon Heavy—was a secret, hardly; it’s been known to be in development for years. Instead the surprise is because of the price and capability. The Falcon Heavy should be able to lift a staggaring 53 tonnes1 into space at a much, much lower cost than we’re used to thinking about for space.
Rockets so far
To add some perspective lets compare this to other rockets, and then to things we know from every day life.
The Space Shuttle, the pride of NASA, can lift something like 24 tonnes into low Earth orbit (LEO). 24 tonnes is about four elephants, or about 48,000 cell phones. It’s about a city bus filled with 20,000 lbs of flour. This has allways been seen as a major lifting capacity. It’s about the best that humans have been able to do so far.
ESA’s big rocket, the Ariane 5, can lift 21 tonnes to LEO, almost as much as a shuttle. Similarly, the Russian Proton rocket can lift about 20 tonnes.
Most of the big rockets out there have about this much capacity, because as you start to get bigger it gets exponentially harder to build. If you want to add a little extra payload, then you have to add more fuel. But if you add more payload, and more fuel, then you have to add even more fuel to account to for that, and so on. This gets out of hand very quickly.
NASA’s current biggest rocket is the Delta IV Heavy. But it can still only lift just shy of 26 tonnes to LEO. It can, however take 13 tonnes to geosynchronous transfer orbit, which is very useful for communication satellites. This is the most any current rocket can take that high.
25 tonnes is a lot of stuff. It’s enough food for an average person for live off of for a year, more if the food is freeze-dried like astronaut food. It’s enough water for three years, with no recycling. This means that one Delta IV Heavy can lift enough food and water for one astronaut a year (1/3 water, the rest freeze dried food).
The biggest rocket ever, by just about every metric, is the Saturn V that took us to the Moon. It could lift an outlandish 119 tonnes to LEO. Since it was designed to go to the moon, this number is not particularly useful. It could only carry 45 tonnes all the way to the moon.
Still, by any account the new SpaceX rocket (if it makes it off the ground as promised) will be an awesome rocket. It’s gigantic, with 27 rocket engines! Their press release says they can lift the equivalent of a Boeing 737 fully loaded with passengers and baggage (by mass, not by volume). I think that’s cheating a bit because airplanes are built extremely light for their size. Another way to look at it is the Falcon Heavy can only lift a quarter of a whale. The average adult blue whale can weigh as much as 180 tonnes. None the less, the only thing larger ever to fly to space will have been the Saturn V, and it won’t be the largest by a whole lot anymore.
The founder of SpaceX, Elon Musk, is pretty open about his intention to send people to Mars one day. I don’t doubt that this rocket is a step in that direction. It could lift enough supplies into LEO for a couple of astronauts for two years. Two years is enough time to get to Mars with current technology and get back.
1A tonne is a metric ton: 1,000 kg. Roughtly equal to a (English) ton, but it’s metric!