# An ion propulsion engine and a little improvement every day

_A thought about ion propulsion, startups and the small improvements that add up over time. What happens after you put everything into getting started?_

By Rishikesh Ranjan · 2026-09-10 · https://rishikeshranjan.com/p/what-happens-after-the-big-push

I was thinking about ion propulsion engines and how there's a parallel with startups, product growth, even your career. An engine that keeps giving you a little acceleration at a time. Initially that doesn't look like much, but give it enough time and the change is huge.

I started with nuclear-powered ion propulsion, but the nuclear part doesn't really matter for what I'm thinking about. Dawn used solar power. Its ion engine was so gentle that at full throttle it would take about four days to add 60 mph. Over the mission, though, those little pushes add up to a velocity change comparable to the entire rocket that launched it. [NASA's explanation of Dawn's propulsion](https://science.nasa.gov/mission/dawn/technology/ion-propulsion/).

Four days for that much acceleration. And then it can keep going. That's the part I'm trying to draw a parallel with, because when you're building something, a small improvement today can seem like very little.

A chemical rocket gives you the big push needed to launch from Earth. An ion engine like Dawn's can't do that. So that initial burst has a job. But after you've put so much into getting started, what after that? You're out juice. Tired with exhaustion.

Chemical engines work in space too, and gravity doesn't disappear once you're up there. The advantage of ion propulsion is how much change it can get out of its propellant over time. I'm talking about the difference between that initial push and being able to keep accelerating toward speed of light (i mean towards 1% of speed of light).

I think about taking a moonshot in a startup or in your career and getting tired very soon. You've put so much into that push that you don't have enough fuel left to do much after it. And the thing you're building still needs you to work on it.

I had some pretty extreme startup failure numbers in mind: 95% in the first five years, then 95% of whatever was left in the next five. Those numbers don't hold up. In one US cohort, 50.6% of private-sector business establishments were still operating after five years and 34.7% after ten. That's the group that started in 2013, and it isn't a worldwide startup failure rate. [BLS survival data](https://www.bls.gov/bdm/us_age_naics_00_table7.txt).

Those figures can't tell me that the businesses that closed had exhausted themselves with a moonshot. But the question I was trying to get at is still there. What happens over all those years after you get started? That's where I'm thinking about the little bit of acceleration you can keep giving yourself, or the product you're building.

Because if you keep improving a little bit every single day, it compounds. What you improved yesterday is something you can build on today. In product growth, or in your own work, that can eventually take you much further than the first small improvement seemed capable of taking you.

Getting 1% better every single day is a huge deal if you can do it. The arithmetic gives you about 37.8 times your starting value after a year. That's assuming the same thing really does improve by 1% every day, with each gain building on the last. It isn't a promise that you or your startup will improve like that.

And an ion engine isn't doing that exact compounding either. A steady acceleration adds to velocity over time. The connection I'm making is the small amount of improvement you keep adding, and how much that can amount to when you can sustain it.

I think the parallel is there in building a company, in product growth, in your career. You want to reach that very high velocity eventually. And you need enough fuel left to keep adding to it after the big push.