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Comment by Retric | Hacker News Reader

The Apollo program also killed people. https://en.wikipedia.org/wiki/Apollo_1

Taking risks is reasonable, but in the end this is still a vanity project. IMO, figuring out how to do self sustaining spaceships / habitats is much more useful long term than going back to the moon using giant chemical rockets, stored food and oxygen etc. Even just orbiting Mars and coming back without landing would be a new achievement.

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Well, if you want to know whether it's worth the risk, I think the best people to ask are the astronauts, and they are chomping at the bit to go.

As far as I can see, there isn't much point to going around Mars just to go. You could just go to a high Earth orbit (or Lagrange point), and gain similar experience, with better communication. The ISS has spent 20 years in low-earth orbit; we're not going to learn much more from it or a similar station.

Apollo 8 and 10 both went to the moon without landing, doing that on a multiple year mission does seem wasteful. However, there are a host of things to test.

From an engineering perspective going to mars orbit means far less sunlight which means a host of new problems. An engine and fuel system to get there would be new and could also be used to send a lander for future missions.

IMO, the Moon might be closer, but Mars is a much better target for long term colonization due to an atmosphere, shorter day, higher gravity, etc.

You meant lower gravity, right? Mars is smaller then Earth.

Sounded like his comparisons were for Mars vs. the moon.

The Moon could be the starting point for Mars colonization. Also, it would make a huge difference if the new Moon missions took advantage of the ISS, which the Apollo missions couldn't count on. One thing is bringing all crew, supplies and equipment from Earth in one trip, and a whole different thing is sending everything on/around the ISS using unmanned cargo missions, then assemble the lunar mission ships up there and send the Moon astronauts when necessary. In other words: Earth<->ISS, then ISS<->Moon<->Mars and/or ISS<->Mars.

For Mars you want people to go up last so they minimize the time spent in zero g. Docking supplies on the ISS is also pointless.

The ISS is not in a useful orbit for a Mars trip and whatever your sending there can make the trip in the same thing you send into orbit. Trying to shoehorn in the ISS just make the trip more expensive and complex.

I agree that Mars is better, but Starship is for Mars. If NASA pays for development, that is moving much closer.

Chemical rocket are the right technology for the inner solar system. And big one and specially reusable have advantages and we know nothing that could potentially be cheaper.

Part of this whole moon approach is absolutely about sustaining the long term. Have you ever read the Artemis program concepts? It is very much about using commercial capability to develop moon resources.

You can't start with producing food, if you make the system depended on that it will fail. One you can actually land on the moon or mars with SIGNIFICANT payloads you can actually start to test out system for large scale food growing and things like that.

Getting to Mars on chemical rockets is not that bad, especially if you can accept a launch window every 15 years. Getting people to and back from low Mars orbit with chemical rockets on a more flexible schedule takes a lot more fuel. It’s clearly viable, but for that kind of DeltaV across such a long trip, solar powered Ion thrusters have several significant advantages.

As to growing food, for on a single mission it’s not that critical, but if you’re sending several missions to Mars unused supplies from one mission can be used on the next mission. Further, the difference between survival and comfort adds up to a lot of food.

Cheap Mars launch windows are every 26 months, not 15 years.

Cheap is relative, Earth years and Mars years don’t evenly divide, so the 26 month cycle is fairly good but not optimal if your willing to wait.

You can go every 26 month. If you can produce fuel on Mars going back is way easier then going from Earth to Mars. You don't go from Mars Orbit, you take of from the surface directly to earth where you aerobrake. No Orbit operation on Mars needed.

> It’s clearly viable, but for that kind of DeltaV across such a long trip, solar powered Ion thrusters have several significant advantages.

Not really. The only potential use for ion thrusters is for cargo transport that is not time depended. If you do that you need to figure out how to do the landing, so the complexity is just higher. The thrust is just to low compared to a few powerful chemical engines. If you can refuel in earth orbit for cheap you are gone be way better off with chemical.

If you move on from chemical, nuclear thermal is by far the best option.

Food is really not the problem. The mass of food needed for humans is pretty small. Clearly you want to produce food on Mars eventually but its not a priority for the first 5 to 10 years. Refuel on Mars is by far the biggest mass saver.

Individual ion engines have been built up to 1.1 lbf for 100kw. Over 2 weeks that’s 9.8m/s * 60 * 60 * 24 * 14/ mass that’s 1.2 km/s for a 10,000 lb spacecraft. And nothing says you can’t use more for a larger spacecraft.

For comparison the ISS’s solar panels are over a decade old and still generate 240kW in direct sunlight. So, you could easily reuse those panels for multiple trips, though power output is cut in half near Mars.

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