At TFL, we're making journeys safer for everyone, and that includes improving safety on London's roads.

That's why we and London boroughs are lowering more speed limits to 20 miles per hour,

because 20 miles per hour roads have already reduced collisions resulting in deaths or

serious injuries by 24%. That is how we're making journeys in London safer and brighter for everyone.

Such TFL improvement plan to the Mayor of London and TFL every journey matters.

This is CBS I Am the World. I'm John Bachelorette, a hotel Mars episode in. Dr. Space,

David Livingston is here of the Space Show, my colleague and co-host and co-pilot,

and we're headed into the future. Thanks to the Vice President of Princeton Satellite Systems,

Stephanie Thomas, who is here two years on to help us understand where direct fusion

drive is right now in development. This is fusion rockets. Fusion rockets are under development.

You can look them up. A theoretical design for a rocket driven by fusion propulsion that could

provide efficient and sustained acceleration in space without the need to carry a large fuel supply.

Stephanie, a very good evening, too. Our last conversation talked about the benefit of not having

to carry a lot of fuel and going faster. It's two years later. Where is the development

of a direct fusion rocket? I understand there are two kinds. Where is the development of both

kinds? Thank you very much. Good evening, too. Hi, John. Thanks so much for having me.

You're right. There are two main kinds, shall we say, or two main ways of using that fusion energy.

Number one, we could make electricity and then connect an electric propulsion system to it.

But even better is a mechanism for taking that fusion energy and putting it directly into your

propellant. By bypassing that electricity generation step, we can make the engine lighter,

which means we can have more room for payload and really increase our payload fraction.

And because our engine is lighter and you got to bring it with you when you're traveling through

...