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Do spacecraft really have to endure the hazards of reentry?

This is the distinction between contra-grav (which makes the item "have no weight", but it does have mass), and "gravitic thrust", manipulating gravity in order to provide thrust.

With contra-grav, you can just lift the bridge up "from the proper points" as high as you want. Specifically, you do not need escape velocity because, by definition, with contra-grav, you are already, essentially, at escape velocity. So, even streamlining isn't an issue, as you can travel slow enough for it to not be an issue. (Modulo however fast winds travel in the upper atmosphere, honestly I have no idea.)

Gravtic thrust is no different than rockets or anything else. Here you DO need escape velocity, you DO need to be going "very fast", and this the "streamlining" of the bridge will impact the success or not of trying to get to orbit.

The happy path is a combination of contra-grav and gravitic thust so that you can move and accelerate within the gravity well of the planet, but with a body that is weight neutral. The gravtic thrust is nice because, unlike rockets, it's doesn't incinerate, well, everything.

And it's much easier to brake.
 
whartung said:
This is the distinction between contra-grav (which makes the item "have no weight", but it does have mass), and "gravitic thrust", manipulating gravity in order to provide thrust.

With contra-grav, you can just lift the bridge up "from the proper points" as high as you want. Specifically, you do not need escape velocity because, by definition, with contra-grav, you are already, essentially, at escape velocity. So, even streamlining isn't an issue, as you can travel slow enough for it to not be an issue. (Modulo however fast winds travel in the upper atmosphere, honestly I have no idea.)

Gravtic thrust is no different than rockets or anything else. Here you DO need escape velocity, you DO need to be going "very fast", and this the "streamlining" of the bridge will impact the success or not of trying to get to orbit.

The happy path is a combination of contra-grav and gravitic thust so that you can move and accelerate within the gravity well of the planet, but with a body that is weight neutral. The gravtic thrust is nice because, unlike rockets, it's doesn't incinerate, well, everything.

And it's much easier to brake.
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In my case I am leaning towards the neutralization of mass as the primary effect of the mdrive, with heat exhaust from the reactor as micro thrust against effectively a few kgs. Higher g thrust is just a greater divisor dropping the weight even further.

Handy on several levels, but mostly against the 1000 diameter gravitic drive limit. No limits in deep space, gotta have Oort.
 
Even without contra gravity, you don’t need the high speed reentry.

If you have >1g thrust you can hover. (down from orbit or up to orbit)
Which means you could slow down to a hover in orbit and slowly land.
The only reason we don’t do that nowadays is because it consumes way too much fuel. But with fusion powered grav engines, the fuel isn’t an issue.
 
Krikkitone said:
Which means you could slow down to a hover in orbit and slowly land.
Click to expand...
Basically ... THIS ... FROM ORBIT ...

w8vCiTQ.gif


You simply need enough maneuver thrust, pointed in the right direction, to let you do this VTOL trick.
With a spacecraft, the sky's the limit.
With a starship, the jump points are the limits (kinda).
 
Jame said:
Which is why, for MTU, a ship like the Mercenary Cruiser can land in an atmosphere.
Click to expand...
There is a hitch - if the atmosphere is half a bar or more in pressure at surface, odds are good there will be winds aloft of significant speed, which can be a problem for certain hull shapes, and can result in a controlled location of landing much harder to accomplish. Likewise, certain surface structures can result in spectacularly potent windflows... (The Kenai and Alaska ranges have some spectacular terrain-prevailing wind interactions... some are lethal... I've lost two acquaintances to the bizarre airflows causing aircraft failure.)
 
aramis said:
There is a hitch - if the atmosphere is half a bar or more in pressure at surface, odds are good there will be winds aloft of significant speed, which can be a problem for certain hull shapes, and can result in a controlled location of landing much harder to accomplish. Likewise, certain surface structures can result in spectacularly potent windflows... (The Kenai and Alaska ranges have some spectacular terrain-prevailing wind interactions... some are lethal... I've lost two acquaintances to the bizarre airflows causing aircraft failure.)
Click to expand...
Sounds like a good time to call for a Piloting skill check!
 
This series seems relevant to this topic (particularly the third video) ... 🤔




This is what the state of the art "reusable" surface to orbit to surface vehicle engineering looked like when CT was being written in the late-70s/early-80s @ TL=7 ... where maneuvering power "didn't last long" (because, chemical rocketry) and aerobraking was required for a zero acceleration inertial entry into atmosphere.

It's kind of remarkable to think about what having access to fusion power and maneuver drives (for nearly unlimited delta-v and acceleration duration for our purposes here) actually means, simply because the endurance of any acceleration maneuvers can be measured in WEEKS rather than MINUTES ... which makes ALL THE DIFFERENCE IN THE WORLD to the maximum engineering stresses that have to be put onto spacecraft transitioning from surface to orbit to surface, repeatedly.

Being able to "geosync in low orbit" thanks to fusion power, maneuver drives and gravitics changes EVERYTHING. 😲
Being able to Stop, Then Land in a VTOL fashion means that there is a LOT LESS (orbital) energy to bleed off upon atmospheric entry than the hypersonic aerobraking route to CTOL option that involves Landing, Then Trying To Stop (in time, before you run out of runway).

The fun part is thinking about how Streamlined hull configurations would be able to "balance" these factors (maneuver braking plus aerobraking) in order to make much more rapid descents through atmosphere from orbit to surface than the alternative for Partially-Streamlined hull configurations (offer not valid for Unstreamlined hulls!). By making "powered descents" through atmospheric entry, Streamlined hull configurations would reduce engineering stresses on their hulls (max-Q pressure, thermal load, etc.) while also being able to take advantage of a "friendlier" aerobraking maneuvering envelope as they descend from orbit to surface through atmosphere (UWP code: 2+).
 
IMG_4191.jpeg

The California Science Center down here in Los Angeles houses the Endeavor.

Starting Jan. 1, they're transition the display from what is shown here to mounting it on the fuel tank with the boosters in launch position. So, December was the last time to see it with the old display.

Here, you can see they already have the boosters in place, the nose cones and tank comes later. They were talking about lifting the orbiter up this week, but I don't know if they managed to get it done, or if they're waiting for the storm to pass.

Once mounted, they will build the rest fo the building around the display.

IMG_4210.jpeg

It was awe inspiring to walk around and be that close to the orbiter. The new display is going to be amazing when it open (dunno if it's this year or next year).
 
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