Maximum Mass Of A Scifi SSTO Versus The Most Common Mass and Crew Complement...

[Spacescifi]

 

So I was designing a scifi SSTO. It has a drive core that requires a mass of at least 30 tons in order for it work at all to get the reaction that causes the scifi drive to work.

The drive core is a single solid unit.

30 tons of drive core can propel 300 tons of spaceship at a maximum of 3g. Indefinitely so long you have electricity running.

No propellant required.

If you had a 1000 ton vessel you would need 300 tons of drive core to allow you to do 3g, and so on.

Mass limits: Despite the ability to generate a lot of thrust and indefinitely at that, I think the real limit to the scifi SSTO mass is the drive core itself. Because it will be the single heaviest object on your entire vessel and will effect it's center of mass... or rather it WILL be it's center of mass.

Too heavy and the ship's floors won't able to support it under thrust as it would fall through and tear through the ship's rear as it accelerates.

Main Question: I could totally see 300 ton SSTOS being common, because making a floor that could support a 30 ton object is feasible. What amount of crew sounds reasonable for a 300 ton SSTO?

30? 40? 50? More? Less?

 

 

 

 

 

[Shpaget]

47 minutes ago, Spacescifi said:

Too heavy and the ship's floors won't able to support it under thrust as it would fall through and tear through the ship's rear as it accelerates.

You have a society capable of making magical drives, but worry about their ability to soundly engineer the floors?

Just don't have your core sitting on the floor, but rather the floor sitting on your core. Problem solved.

 

[Spacescifi]

32 minutes ago, Shpaget said:

You have a society capable of making magical drives, but worry about their ability to soundly engineer the floors?

Just don't have your core sitting on the floor, but rather the floor sitting on your core. Problem solved.

 

Not really, unless you are proposing putting the core itself at the rear end on the outside of the vessel.

[Shpaget]

Why is that a problem? Propulsion system attached directly to the core, in line with propulsion vector. The rest of the ship is built around it, everything is attached to the core, add a bit of cosmetic plating so the core is not "outside".

[farmerben]

Static structure relative to the engine and hull should not be difficult.  A floor that is 300 tons at 3g will need to support 900 tons.  That means steelwork on the scale of a large railroad bridge.   It's not far outside the specs of normal seagoing ships, they are designed to take a beating.  If the 3g acceleration is relatively smooth, unidirectional, and vibration free, you should be fine.  Vibrate everything at 3g's and its a different story.

[Shpaget]

For some context, Saturn V and Starship are about 3000 tons. The Nimitz aircraft carrier has two reactors clocking in at about 630 tons each.

Securing a 30 ton object is a problem we've solved a long ago.

[KSK]

Following up from @Shpaget’s post, the combined mass of the Apollo CSM and lunar module was about 43 tons. Peak acceleration of the Saturn V was apparently about 3.9g.

If they could do it in the 60s, I’m pretty sure it’s a problem you could handwave away.

Also, why does the 1000 ton vessel require a 300 ton drive core rather than a 100 ton one?  (Given that the 300 ton vessel requires a 30 ton core). Not that it’s important, I’m just curious.

As for crew capacity, that’s difficult to judge purely from vehicle mass, but if you want some numbers, a Boeing 737 can hold about one to two hundred passengers depending on model, and has a dry mass of just over 41 tons. High gross weight max takeoff is just over 79 tons.

 

Edited February 26 by KSK