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2

I don't think that equation is correct. I don't see the benefits of using $I_{sp}$ when you have the thrust, $F_{t}$. The 1D equation of motion (neglecting drag) is: $a_{b}(t)=\frac{F_t}{m_0-\dot{m}t}-g$ $a_{c}(t) = -g$ Where $c$ and $b$ are the coast and boost phases of flight. Your burn rate, $\dot{m}$, assumption is good, and since it is a constant you ...

4

Of course, but relative to what? For example, consider the rotation of the Earth. At the equator, the ground (with you on it) is moving at 1670 km/hr. You could travel very fast if you "just stopped". But how would you stop? You'd have to somehow start moving 1670 km/hr relative to the earth. That's very very fast. In this case "stopping" ...

1

Fuel for a tug operating in LEO from 255 km to 400 km is extremely expensive. If the fuel needed for the tug plus payload to lift from 255 to 400 km and for the tug only to return to 255 km is more expensive than the payload itself, the use of the tug does not make sense. If the tug is fueled for several lifts, much fuel is used only to move the fuel for the ...

0

Reusable space tugs are coming soon. In the last SpaceX Transporter mission in June 2021, a number of (expendable) space tugs were on board to deploy several Cubesats into more precise orbits: D-Orbit's Wild Ride with a chemical propulsion system SpaceFlight's Sherpa LTE with an Apollo Hall Thruster Engine Momentus's Vigoride space tug using their water-...

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Patrick Neumann told me they had to raise a bunch of cash in order to pay for ride and slot on the Airbus/ESA Bartolomeo module for the ISS. I suspect they weren't able to do it in time and had to find other ways to perform a flight demonstration. See https://neumannspace.com/the-spirit-mission-is-a-go/ which describes their scheduled first flight on a 6U ...

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