3 ms·

Very cool. I love seeing development in commercial non-chemical-propellant technologies. Question about the total impulse. For ND-500+, they claim up to 250k

Very cool. I love seeing development in commercial non-chemical-propellant technologies. Question about the total impulse. For ND-500+, they claim up to 250kNs of total impulse and a wet mass of 10-20kg. Assuming a spacecraft mass of about 100kg, and a fuel payload of 10kg, that's only about 2000m/s dV. Not enough to go to Mars, but enough to extend an LEO mission or to send a tug to deorbit space junk. Anyone know how much one of these might cost?

fnordpiglet 3y ago
I would note that delta v from LEO to mars orbit is 7500m/s, which would only need ~40kg of fuel from your calculations (didn’t recalculate with additional fuel mass, ymmv). That doesn’t seem outrageous.
trhway 3y ago
>up to 250kNs of total impulse and a wet mass of 10-20kg The specific impulse here is 3-6 times better than the one of chemical. Considering the existing tech the solar+ionic seems to be the best option for going to Mars. With some very feasible development of existing tech the nuclear+ionic seems to be the best for farther into Solar and beyond (if I didn't make large mistakes https://news.ycombinator.com/item?id=38445404 https://news.ycombinator.com/item?id=38445404)
schiffern 3y ago
> For ND-500+, they claim up to 250kNs of total impulse and a wet mass of 10-20kg Wouldn't bet on it. The same PDF on their website[0] claims an Isp of 2500 seconds. If you do the math (I=mv), the propellant mass works out to 10.2 kg. So at the low end of their "10-20 kg" estimate, 102% of the total thruster mass would need to be the eroded solid propellant, leaving a -2% mass budget left over to cover the power supply, capacitors, control electronics, and all non-eroded structures. That seems... optimistic. The technology seems cool, but putting trivially impossible numbers on your launch website is a big red flag. [0] https://web.archive.org/web/20231221000314/https://neumannspace.com/wp-content/uploads/2023/09/Neumann-Drive-Datasheet_Sept-2023.pdf https://web.archive.org/web/20231221000314/https://neumannsp...

fnordpiglet 3y ago

I would note that delta v from LEO to mars orbit is 7500m/s, which would only need ~40kg of fuel from your calculations (didn’t recalculate with additional fuel mass, ymmv). That doesn’t seem outrageous.

trhway 3y ago

>up to 250kNs of total impulse and a wet mass of 10-20kg The specific impulse here is 3-6 times better than the one of chemical. Considering the existing tech the solar+ionic seems to be the best option for going to Mars. With some very feasible development of existing tech the nuclear+ionic seems to be the best for farther into Solar and beyond (if I didn't make large mistakes https://news.ycombinator.com/item?id=38445404 https://news.ycombinator.com/item?id=38445404)

schiffern 3y ago

> For ND-500+, they claim up to 250kNs of total impulse and a wet mass of 10-20kg Wouldn't bet on it. The same PDF on their website[0] claims an Isp of 2500 seconds. If you do the math (I=mv), the propellant mass works out to 10.2 kg. So at the low end of their "10-20 kg" estimate, 102% of the total thruster mass would need to be the eroded solid propellant, leaving a -2% mass budget left over to cover the power supply, capacitors, control electronics, and all non-eroded structures. That seems... optimistic. The technology seems cool, but putting trivially impossible numbers on your launch website is a big red flag. [0] https://web.archive.org/web/20231221000314/https://neumannspace.com/wp-content/uploads/2023/09/Neumann-Drive-Datasheet_Sept-2023.pdf https://web.archive.org/web/20231221000314/https://neumannsp...