3 ms·

7KW NASA drive weight about 10kg. At 10KW it would expel about 8milligram/second for 0.3N thrust (even with paltry 50% efficiency). It will get ship of 100kg to

by trhway 2y ago

7KW NASA drive weight about 10kg. At 10KW it would expel about 8milligram/second for 0.3N thrust (even with paltry 50% efficiency). It will get ship of 100kg total starting mass to 15km/s in under 2 months spending under 40kg expelled mass. The arithmetic is very simple. (my favorite arithmetic here is 3 stage nuclear powered ion drive ship with increased voltage resulting in ~35000 Isp and thus getting 1000-1500km/s in 100 years, and thus 1000 years fly-by to Alpha Centauri, with the tech basically available today :) >They're also relatively unreliable Given their simplicity i think it is among the most reliable pieces of tech around. 5 years non-stop - no issues : https://www1.grc.nasa.gov/space/sep/gridded-ion-thrusters-next-c/ https://www1.grc.nasa.gov/space/sep/gridded-ion-thrusters-ne... Note that all this is just NASA so far without SpaceX/Musk applying their engineering magic yet which i think would significantly improve the mass, efficiency, etc.

somenameforme 2y ago
Mass = 10,000kg (per the initial topic) Force = 0.236N (per your link) Acceleration = 0.0000236m/s (acceleration = force / mass) Seconds in 2 months = 5259600 Final Velocity after 2 months = 277 miles per hour (0.124km/s) --- This is an extremely naive and optimistic calculation since I'm assuming the engine is weightless and does not require fuel or power. It's easier that way and still emphasizes the point perfectly fine. You're gonna need a lot more engines to get anywhere. And of course a 10 ton ship is not practical. The goal for Starship is to to have a payload in the hundreds of tons, let alone the entire vessel's mass. You also only have half the distance to accelerate, because you then need to turn around and decelerate the remaining distance. And we're also ignoring landing/takeoff which obviously isn't happening.
- trhway 2y ago
  >Mass = 10,000kg (per the initial topic) >Force = 0.236N (per your link) >I'm assuming the engine is weightless and does not require fuel or power. 10KW 10kg engine plus 40 kg expelled mass per 100kg total starting mass. Thus for 10000kg - 1000kg of 100 x 10kg 10KW engines, 4 tons expelled mass, 2.5 tons - solar panels providing power. 1 engine - 0.3N, 100 engines - 30N. 15km/s in under 2 months, plus 2 months deceleration. The same for 100ton ship or 1000ton. >landing/takeoff that is by local chemical Starships "shuttles" which would transfer people and cargo to/from the interplanetary ships. Using Starship shuttles to fuel the interplanetary Starship, though chemical one, has long been in the published SpaceX/Musk plans.

by trhway 2y ago

somenameforme 2y ago

Mass = 10,000kg (per the initial topic) Force = 0.236N (per your link) Acceleration = 0.0000236m/s (acceleration = force / mass) Seconds in 2 months = 5259600 Final Velocity after 2 months = 277 miles per hour (0.124km/s) --- This is an extremely naive and optimistic calculation since I'm assuming the engine is weightless and does not require fuel or power. It's easier that way and still emphasizes the point perfectly fine. You're gonna need a lot more engines to get anywhere. And of course a 10 ton ship is not practical. The goal for Starship is to to have a payload in the hundreds of tons, let alone the entire vessel's mass. You also only have half the distance to accelerate, because you then need to turn around and decelerate the remaining distance. And we're also ignoring landing/takeoff which obviously isn't happening.

trhway 2y ago
>Mass = 10,000kg (per the initial topic) >Force = 0.236N (per your link) >I'm assuming the engine is weightless and does not require fuel or power. 10KW 10kg engine plus 40 kg expelled mass per 100kg total starting mass. Thus for 10000kg - 1000kg of 100 x 10kg 10KW engines, 4 tons expelled mass, 2.5 tons - solar panels providing power. 1 engine - 0.3N, 100 engines - 30N. 15km/s in under 2 months, plus 2 months deceleration. The same for 100ton ship or 1000ton. >landing/takeoff that is by local chemical Starships "shuttles" which would transfer people and cargo to/from the interplanetary ships. Using Starship shuttles to fuel the interplanetary Starship, though chemical one, has long been in the published SpaceX/Musk plans.