Is achievingorbit that easy?

[jacobmuller]

I was doodling an SM+3 design for a reentry* vehicle using Spaceships when the possibility of using it for relaunch occured to me.

Basically, reentry capable only, would be 1 armour, control in both cores for one crew, 3 passenger seats (15 spaces), a soft-landing system and a combined fuel/power and drive section to achieve de-orbit.

But, if you replace 2 passengers with fuel tankage, a streamlined winged design can achieve orbit in a couple** of minutes? I must be doing the arith wrong...

*emergency, sport or military stealth unit.
**eg 2/3 g for approximately 2 minutes.
PS: I understand Spaceships is less accurae below SM+5 but it's not likely I'll be making any reentry vehicles.
PPS: you could replace passenger seats with hibernation or nanostasis modules and travel around waiting for rescue.

[kdtipa]

I haven't read what you refer to (no clue what SM+3 design for reentry refers to), but it's sounding like a winged design. You can't use wings to reach space. The higher you go, the lower the air pressure, and therefore the less lift wings can produce. If the air is thin enough, it just won't support the winged vehicle anymore.

[Langy]

What type of drive did you stick in the little guy? What TL is it? Both of those are rather important questions.

[jacobmuller]

Originally Posted by Langy

What type of drive did you stick in the little guy? What TL is it? Both of those are rather important questions.

Funnily enough, neither are relevant. They only alter cost and time taken to achieve orbit, and whether you need fuel or power plants...
It's all just guesswork for SM+3 but the same ratios apply as if it were an SM+6 design using SM+5 subsystems for drive (plus lots more passengers).

What befuddled me was, according to the numbers I played with, I could build it as 53% fuel tankage, 2/3g of thrust from a subsystem HEDM rocket and fly to orbit in something like 4 minutes? And there'd be fuel to spare.

[Fred Brackin]

Originally Posted by jacobmuller

What befuddled me was, according to the numbers I played with, I could build it as 53% fuel tankage, 2/3g of thrust from a subsystem HEDM rocket and fly to orbit in something like 4 minutes? And there'd be fuel to spare.

I think you've either misread what orbital velocity is or simply broken the system by trying to stretch it too far.

To reach orbital velocity in 2 minutes you'd need to pull a steady 6 Gs and wings don't change that.

[jacobmuller]

Originally Posted by Fred Brackin

I think you've either misread what orbital velocity is or simply broken the system by trying to stretch it too far.

I've definitely broken the rules by going below SM+5, but it was fun, and I got a better grasp of the rules and a simple TL9 space shuttle
(bumping the scale up to SM+6 would allow 2 crew, 10 passengers and 1.7ton cargo and be within RAW - don't know if it'd be econonical but that's a different thread).

[Anthony]

Originally Posted by jacobmuller

What befuddled me was, according to the numbers I played with, I could build it as 53% fuel tankage, 2/3g of thrust from a subsystem HEDM rocket and fly to orbit in something like 4 minutes? And there'd be fuel to spare.

Aha. We now see. Yes, if you have HEDM rockets, getting into orbit is trivial. Sadly, we don't have HEDM rockets today, nor do they look all that likely in the near future.

[thtraveller]

Originally Posted by jacobmuller

What befuddled me was, according to the numbers I played with, I could build it as 53% fuel tankage, 2/3g of thrust from a subsystem HEDM rocket and fly to orbit in something like 4 minutes? And there'd be fuel to spare.

You can create a standard rocket with 45% fuel and a HEDM drive in G:Spaceships that makes orbit. It's the HEDM bit that makes it "easy". Or you can do it with an external pulsed plasma (Orion) drive with only 10% fuel.

[Crakkerjakk]

Originally Posted by thtraveller

Or you can do it with an external pulsed plasma (Orion) drive with only 10% fuel.

TL 7 interplanetary flight, baby!

[jacobmuller]

Originally Posted by kdtipa

I haven't read what you refer to (no clue what SM+3 design for reentry refers to), but it's sounding like a winged design. You can't use wings to reach space. The higher you go, the lower the air pressure, and therefore the less lift wings can produce. If the air is thin enough, it just won't support the winged vehicle anymore.

I refer to my own doodlings and guesstimates/ extrapolations from Spaceships tables.

According to Spaceships, on page 37 and 39, you can make it to orbit in an atmosphere if you have wings. It provides formulae for time taken. I think the idea is that by the time your lift medium is gone, you're high enough that your thrust exceeds gravity at that altitude, but I'm just guessing.

I started out to design a cheap tin-can for escapes from spacestations and ended up discovering a space-taxi.