Bootstrapping

Bootstrapping is a very important aspect of getting the cost of starting a tether down to an affordable prices. The general idea of bootstrapping is to start by sending up a limited LEO tether with an existing expensive rocket, and then use our reusable rocket to grow the tether from there. The initial tether will have limited solar power, limited thrusters, and have a smaller payload weight limit. The limited solar power and thrusters will mean it takes longer for the tether to replace the energy used in picking up a payload. So we can not launch payloads as often initially.

The SSTT rocket can be used even with this limited initial tether, just not will full payloads. When a rocket flys with a smaller payload, it can get to a higher velocity, so reducing somewhat velocity/energy the tether needs to provide early on. Since the SSTT rocket is reusable it will still be much chaper to operate per pound even though it is only lightly loaded.

As we bring up more solar power and more thrusters we will be able to launch more often. As we bring up a stronger tether we can have higher tether tip speeds and lift larger payloads. Starting out with a limited tether, it only takes a few months to grow to a much larger tether using the initial tether and the rocket designed for the larger tether.

While bootstrapping, the orbit eccentricity, amount of ballast, and tether strength determine the maximum load. The total cargo per day is determined by the amount of solar power, the thruster efficiency, and the delta-V being given to the cargo.

The natural toss from the tether will have too much energy to toss to itself, but it is possible to use aerobreaking to reduce the payloads energy before it is picked up by the ballast.

Current Costs vs Tether Lift Costs

Current cost is around $2,000/lb to get anything into orbit. Our costs to lift something to orbit with a tether could be very low, maybe $20/lb (though our price to others will be higher). If we start with a very small tether and ballast it will not initially be able to handle a full load from our rocket. So initially the reusable rocket would fly only partially loaded. If it was 10% full, our costs could be on the order of $200/lb. This is still far cheaper than existing ELVs. So we can save big if we can start using our tether and SSTT right away. As the ballast and tether get bigger, the rocket can lift more on each flight.