Launch HN: Radical (YC W23) – Autonomous high-altitude solar aircraft
Our aircraft is designed to fly over specific areas for months, carrying various payloads for tasks like imagery, sensing, and telecommunications. What we’re building behaves like a drone in some ways, and like a satellite in other ways. Much like satellites, we’re able to provide service for long periods of time, but we’re also much closer to users (we fly at around 20 km altitude) and able to maneuver or remain over an area of interest. This makes what we’re building really well suited to applications that require continuous coverage or high-resolution/bandwidth data.
Examples of this include continuous real-time monitoring (such as in wildfire management or illegal fishing), high-resolution mapping and imagery (we’re able to collect sub-10 cm resolution imagery), and high-speed direct-to-device internet. The ability to permanently host sensors and devices in the sky in this way opens the door to lots of new opportunities. In truth, we still don’t know all the new applications that will arise from this (we’re really interested to hear your thoughts on potential applications!).
As for the technical details: Our aircraft is battery electric and driven by propellers. It has a large wing for high aerodynamic efficiency and to generate the necessary lift required to fly in the thin air of the stratosphere. The wing is covered in solar cells, during the day, these power the aircraft and charge its batteries. Through the night, battery energy is deployed to continue flight. We repeat this process daily, enabling us to fly for up to a year without needing to land. Ultimately, battery cycle life is what limits our aircraft’s flight endurance - and we can land, carry out simple maintenance tasks and then re-launch to continue flying. Our aircraft has multiple tails which help to stabilize the ultra-lightweight structure (our 20 ft. prototype weighs just 13 lbs.). We also use these tails to control the aircraft, they provide roll control by twisting the main wing of the aircraft, increasing or decreasing lift as needed.
The aircraft is fully autonomous; it has a full autopilot system onboard and various sensors for position, airspeed, and other key data streams (much like a typical drone or UAS). The aircraft flies at high altitudes of around 70,000 ft. (20 km) avoiding cloud cover, civil air traffic, and the turbulent winds of the troposphere.
Long endurance flight has been the goal of many past projects. NASA’s Helios and the DARPA Vulture program tried to develop long endurance aircraft. Helios’s crash led to an overhaul of aircraft structural analysis codes, and DARPA Vulture led to advancements in battery and solar tech. More recently, both Facebook’s Aquila and Google’s Loon were discontinued. Recent advancements in battery and solar tech, and miniaturization of electronics mean long endurance flight is now feasible - but we are aware we need to do things differently to succeed. Unlike those before us, we’re not tying ourselves to a single application and are focused on bringing a cost-effective solution to market. That means avoiding research-grade components and moving quickly. Additionally, we firmly believe that iterat...
205 comments
[ 3.2 ms ] story [ 238 ms ] threadCongrats on the milestone & keep on pushing!!
Besides that "high-speed direct-to-device internet" caught my attention. Are you planning on competing with Starlink? Is 20km high enough to cover a big enough area?
In terms of coverage, from that altitude, we have good line of sight coverage over large areas. Obviously, satellites can cover wider areas, but it turns out that in most suburban/rural settings the ground footprint becomes limited by the population density and bandwidth available - so the larger satellite footprint is only really useful in extremely remote locations.
>we then spent 6 years working together on delivery drones at Amazon Prime Air
Was that ever a serious endeavour or just a publicity stunt?
Perhaps unexpectedly, climbing to 20km altitude isn’t too large a problem from an energy perspective. In a typical energy cycle, the aircraft has low battery in the morning, so if we launch with a full battery charge we have plenty of extra energy to climb up to altitude.
Prime Air - definitely a serious project, but I’m sure Amazon didn’t hesitate in milking the PR! Making a reliable drone delivery service at Amazon scales certainly isn’t easy. That team is still going strong and I’m sure we’ll see more from them as they ramp up commercial deliveries.
That's fine, but I think you need to make that clear or some people might think you aren't being straight.
I have purely cosmetic feedback about the website, which is that the tagline "from the stratosphere" doesn't match up with the images being played behind, which are pretty clearly low altitude. I am assuming that's because it was easier (or possible whatsoever) to film lower, but it gave me a little mental hiccup.
I look forward to seeing what y'all come up with!
Thanks for the website feedback - for the sake of clarity, our test flights with the sub-scale aircraft have all been at lower altitudes. The stratosphere is the next step and we plan to fly there next summer!
Can we make sure someone (if not you guys) fully builds this service on your flights for the fire service?
One of the few things that are not obviously, if in any way at all, usable for any military purposes is targeted advertising. Whether it's used by the good guys more is an interesting topic.
Of course I have no idea if this is feasible or not, but I assume someone here will correct me if I'm pipe-dreaming.
Planet has the spatial resolution but not the temporal resolution.
NOAA has the temporal resolution but not the spatial resolution.
Please correct me if I'm wrong.
TBH I thought they had 15cm, but for human-scale large object monitoring (fires, traffic, construction) 50cm is enough.
There are other fields where 10cm resolution is required though, obviously.
I don't know how much you can share, but I'm curious about the solar and battery system.
Are you using silicon cells, multi-junction cells, or something else?
What sort of battery chemistry do you use? It seems like deep battery cycling is a must to keep weight under control, but battery degradation is probably the limiting factor for mission duration. The low temperature in the stratosphere also seems more challenging than what terrestrial vehicles deal with.
Edit: Funny, they didn't mention Airbus anywhere. But they do have the perfect founder background, Amazon Air and delivery drones. Sells good with VCs, but so far they have to get real aircraft in the air.
They’re the perfect scrappy startup with fast iteration cycles.
We’re using conventional silicon solar cells, rather than the GaAs cells used by Airbus. We give up some efficiency by doing this, but it keeps costs far lower - which we think is key to iterating quickly, and opening up some of the market use cases.
Similarly, we’re sticking with conventional battery chemistries (Lithium Ion). Battery energy density is by far the biggest driver for this technology - in the past decade we’ve seen huge advancements in battery tech, which is one of the reasons this technology is now possible. As you identify, cycle life is a key challenge and what will limit the aircraft’s endurance.
So you want to beat Airbus but also be cheaper. And do it with off-the-shelf components too, because those specialized ones are just too expensive. Not to say it's impossible but wow
If you've worked in both a startup and a large corporation doing R&D, it's really obvious that startups are far, far more effective at it. If you gave $10m to a startup, vs a budget in a corporate project, you'd probably get 10x the result from the startup.
Where corporations excel is in scaling things up. Once you have a good design, you need a good manufacturing process and a solid supply chain. Startups rarely have the capital or knowledge to put that in place, while big engineering corporations will.
I too would like to see more autonomous hydrogen balloons flying. Even on tethers to get height cheaper than a tower.
You could either detach from the balloon, or use spare solar power to deflate the balloon in case you need it again. Maybe the balloon could help maintain altitude at night.
My gut feeling tells me this airplane is potentially cheaper than a rocket, so if it is shot down, it is a win already. If it detects launcher position while rocket is on the way it is even bigger win. Potentially it reveals larger radar position too, that's another win.
It is difficult, expensive and risky to jamm objects at that altitude. In the current Ukraine-Russia war russians would probably not bother jamming it.
So, what these guys are developing certainly is a military technology. No way around this. High endurance, high altitude cheap aircraft will sell like hot cakes.
But this thing could be fitted with frequency-hopping comms, and could control a swarm of attack drones from 70,000 feet. It could also have a backlink to the pilot, allowing him to control any drone in the swarm.
I imagine the Ukrainian nerds are already all over this sort of idea.
There’s a good reason why most airplanes look and behave alike: because it works. Technology choices like flying wings (not used here) or twisting wings (used here) are a “code smell” to my computer programmer nose. To me, nothing is sexier than good reliable technology that works. Smart investors will know that. The other ones will do you a favor by staying away.
The use of batteries to maintain altitude at night is a big concern. Batteries are heavy and will dramatically cut down on the usable payload. They need to be maintained warm (but not too warm!), which is a challenge at the low ambient temperatures the aircraft will experience while flying.
Most airplane accidents happen during take-off and landing. Please do not shortchange these phases of flight, and good luck.
Batteries are heavy, but if you want to conduct long endurance flights - greater than a few days, then realistically they are the best option.
That’s the obvious use case for this technology, right? Cheaper and more easily retargetable than satellites. Longer duration, quieter, and more resilient than manned aircraft, but not fast or maneuverable enough to survive in contested airspace.
So that leaves large area, long term surveillance in uncontested conditions as the prime use case.
Sounds an awful lot like cops or an occupying force putting a fleet of these up to indefinitely track all movement or signals over entire neighborhoods or cities. Do you plan to market and sell your technology for this use?
They actually did do a surveillance experiment in Dayton Ohio in 2014: https://www.washingtonpost.com/business/technology/new-surve...
My biggest concern would be weight & power. This plane only works if it stays light and doesn't use a lot of power. If the military wanted this for live video or EO/IR, how would that communicate with ground sensors? KU satcom, UHF? Will it have IFF onboard, will it meet all the no-single-point-of-failure requirements? Everything the military requires will start using up a ton of power and adding a ton of weight. I get people always think these things will be used for evil, but it isn't exactly easy to take something civilian and suddenly ship it off to some USAF squadron.
YC's reputation depends on and is justified by its investment portfolio. Its investments are not justified by its reputation.
I do wonder about the payload capacity, it seems like it might be quite small given the batteries and the limited performance available from the altitude.
Winds will be a bigger issue than energy when climbing. Up at 20 km (70k ft.) winds are quite calm, but we need to ascend through more turbulent winds as we climb. We’re sizing our MVP around this.
Also, in engineering it's pretty common to use it these days, even in the US.
Amazing work! Super excited to follow along!