Adam Hibberd
Yesterday I was trying to gauge the measure of the SpaceX Starship in terms of its ability to launch the Project Lyra spacecraft on its way to its destination.
BTW Project Lyra is the initiative to send a mission to catch-up with very rapidly receding interstellar object 1I/’Oumuamua. So exactly how do we get a probe to intercept this object?
Well I discovered ages ago that whatever mission plan we might adopt; a visit to the planet Jupiter, either as a means-to-an-end, or alternatively to exploit it directly by delivering a Jupiter Oberth Manoeuvre would be vital in achieving the mission goal: 1I/’Oumuamua.
So how does the Starship fare as far as lofting a payload that will eventually reach Jupiter is concerned?
The unfortunate answer is not very well. This answer is important because this super-heavy launch vehicle is designed as a part of Elon Musk’s initiative to colonise the planet Mars, which involves an Earth escape (hyperbolic) orbit just like Project Lyra’s – though obviously the former escape is to Mars and the latter is to Jupiter.
So what’s holding it back?
The straight-forward answer is the choice of Starship’s propellants which are methane and oxygen as opposed to the likes of alternatives like NASA’s Space Launch System (SLS) which employs the much more powerful, and efficient, LOX and LH2 combination of cryogenic propellants.
It seems that Starship’s methane/LOX combination is ideal for inserting a payload into LEO (Low Earth Orbit), from which the Starship can then be refuelled and sent off to any destination within the Solar System without much difficulty, but absolutely pants at injecting a payload directly into an escape orbit from launch.
To be fair, Elon Musk has made it quite clear that Starship was designed with this refuelling strategy in mind, but there is a cost, which one would expect for any decision along these lines.
The cost is indeed financial – it would take on the order of 10 Starship tankers filled with the requisite methane+LOX in the cargo bay to fully refuel ONE Starship located in LEO – the logistics and economics are a tough reality check for anyone who has bought into the glib Mars colonisation rhetoric spouted by Elon.
So where does this leave Project Lyra? Well I shall continue my research into using a Starship launch vehicle, and I shall have to add two or even three extra stages to the Project Lyra craft payload itself.
If you are slightly concerned by this profligate use of rocket stages, have no fear, there is plenty of space in the Starship’s huge cargo bays for these rocket stages + the Lyra craft.
Hi Adam, you need to take into accound the reduction in cost from having a rusuable Starship. If the launch costs are brought down to 20 million per launch, as they are supposed to be, you can launch one Starship kick stage (mass optimised without wings and thermal shield) and nine tankers for 200 million dollars, so about 5 times less expensive than a SLS launch. However, another way of looking at this is that after a single launch you have a 100+ tonnes of ‘something’ in orbit. That’s the vehicles that needs to do better than Methane+oxygen, or indeed hydrogen+oxygen. And that X vehicle only costs something like 20 million$ to get to orbit. Another possibility with the Starship architecture is that you design a low cost vehicle, such as the WaveRider,that would fit easily into the Starship fairing, could go as a very low rideshare and sent you probe off at 200 km/s (provided the concept works, of course!). There would be a very small kickstage required, probably the most costly part of the whole thing, to raise the Windrider out of the ionosphere so it could actually get to the solar wind. Or go on a Moon rideshare, and pay whatever the cost of a part on that will be. The Windrider can be found easily on Google scholar.
I would love to redesign the Windrider for a Starship launch. It might actually get funded if launching it only cost 100 000$.