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How to make a .80 TWR craft go up in the upper atmosphere?


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3 hours ago, Rocket In My Pocket said:

Ummm... I don't know, is it supposed to be an SSTO?

-Snip-

What is the craft doing?

It is the second stage of a cheap minmus rocket

 

I made a typo in the title, It is supposed to be twr

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If you really mean .8t, then an OKTO2 + small reaction wheel + small nosecone + 3 oscarB tanks + a spark engine will get you suborbital, as a rocket. But that's probably the best you can do.

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Just now, bewing said:

If you really mean .8t, then an OKTO2 + small reaction wheel + small nosecone + 3 oscarB tanks + a spark engine will get you suborbital, as a rocket. But that's probably the best you can do.

...I jsut corrcted my typoo

 

NOTE: misspelling on purpose

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Yeah, saw it.

You can get away with having a TWR of less than 1 if you are already going up quickly -- or if you already have a lot of horizontal velocity, or both.

You don't need to have TWR >1 all the time.

 

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My second stages are usually around that t/w.
First stage is 1.4 t/w and 1700 m/sec DV. It burns out at 45° pitch, 28km altitude, and 750 m/sec velocity.
Second stage is 0.7 t/w, 1600 m/sec DV. It burns out right about LKO.

Best,
-Slashy

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19 hours ago, EndTraveler said:

should it act like an ssto?

SSTO means single stage to orbit, and indicates nothing about how it flies. There are rocket SSTOs, spaceplane SSTOs, and potentially railgunned SSTO, Sky hooked SSTO, Rotary rockets SSTO, Balloon-Rocket SSTO.

 

I guess you meant "as a spaceplane", and yes, at 0.8 TWR, a rocket won't lift up the ground (though it may make a lot of sense to have low TWR on the later stages of a multistage rocket), and plane might. It will need more wings than a more powerfull spaceplane or than a shuttle.

Also, it does not need to be single stage. You can have a plane carrying a smaller plane or a rocket.

 

On small moon with low orbital velocity, it is also possible to ascend with a TWR lower than 1 if you find a flat place (ground resistaance on your wheels replaces lift). It can still be usefull on not so small moons and with TWR a bit over 1.

Edited by Kesa
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For your climb rate to increase,  your

lit from orbital freefall effect 

+

lift from wings

+

thrust component from engines thrusting downward

has to be >     weight of craft

 

So if you're already at 70% of orbital velocity,   a TWR of 0.8 will be more than enough to overpower the craft's remaining weight.

Here is an example of one of my spaceplanes using these effects -

dXSNYCK.jpg

TWR (2 nukes running)  0.44  

1577 m/s so about 75% of orbital velocity

Lift - 115kn

Drag -  35kn

Thrust - 120kn

Weight is shown as 246kn,  but since we're approaching orbital speed over two thirds of that is getting cancelled by the centrifugal force of hurtling around the the planet.  Our climb rate is 147 m/s and increasing..

 

 

 

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