LV-T45 40,000M 1000m/s

[Chopper1066]

I'm doing a mission that requires in flight testing of LV-T45, 40000m 1000m/s. Is there a way of estimating final altitude and speed rather than trial and error? 

[Snark]

9 hours ago, Chopper1066 said:

I'm doing a mission that requires in flight testing of LV-T45, 40000m 1000m/s. Is there a way of estimating final altitude and speed rather than trial and error? 

Hello, and welcome to the forums! 

Moving this question about how to play the game to Gameplay Questions (since "Science & Spaceflight" is about real-life stuff, not KSP).

[ElWanderer]

Before v1.0, I had a spreadsheet that simulated a vertical ascent second by second (or some fraction thereof). Back then, drag was predictable (and highly unrealistic) so this was not only possible with relatively simple calculations, but actually gave useful results. The introduction of a realistic drag model (amongst other things) changed all that.

These days, I'd go with trial and error for anything that involves the atmosphere - the game is itself the best way of simulating. You can even justify (if you feel the need to) a few reverts by pretending you are running simulations ahead of actual missions.

[invision]

based on playing entirely too much 40k at 1000 m/s assuming we are in kerblin will get you to 75-90k into space on a sub orbit before falling back

[bewing]

First, a special note. Your speed meter on your navball can measure two different speeds: surface or orbit. Contracts are always specified in surface speed. Your navball automatically switches to orbit speed in the upper 30 km altitude range. So you will only have a little time to change it back.

Beyond that, for atmospheric contracts, you kinda need to use liquid engines with throttle control. You get up to the altitude you want, and turn sideways. You have the contract app pinned open so you can see the green checkmarks. Then you thrust sideways until you get the velocity you want (the checkmark appears) -- then you run your test quick (if necessary). It's a lot harder if all your velocity is upwards, because you have a much more limited time in the proper atitude range then.

Alternately, you can launch some masses with various SRBs and just make a few notes of the velocities at various altitudes. Then you can downgrade performance by adding a little drag, a little mass, removing fuel, or throttling your engines down a little bit in the editor. But, as said above, the drag during launch completely prevents paper calculations from being accurate enough.

 

[TheFlyingKerman]

9 hours ago, bewing said:

First, a special note. Your speed meter on your navball can measure two different speeds: surface or orbit. Contracts are always specified in surface speed. Your navball automatically switches to orbit speed in the upper 30 km altitude range. So you will only have a little time to change it back.

Beyond that, for atmospheric contracts, you kinda need to use liquid engines with throttle control. You get up to the altitude you want, and turn sideways. You have the contract app pinned open so you can see the green checkmarks. Then you thrust sideways until you get the velocity you want (the checkmark appears) -- then you run your test quick (if necessary). It's a lot harder if all your velocity is upwards, because you have a much more limited time in the proper atitude range then.

Alternately, you can launch some masses with various SRBs and just make a few notes of the velocities at various altitudes. Then you can downgrade performance by adding a little drag, a little mass, removing fuel, or throttling your engines down a little bit in the editor. But, as said above, the drag during launch completely prevents paper calculations from being accurate enough.

 

How about putting the test item inside one standard faring? Then the drag is constant.

IMO a plane or SSTO is the best way to do any atmospheric contracts, though.

[Spricigo]

3 hours ago, TheFlyingKerman said:

How about putting the test item inside one standard faring? Then the drag is constant.

Drag varies with velocity, altitude and crossectional area. Not exactly handy to calculate its effects for each vessel you launch.

[juanml82]

I've been playing science career for several months, so I haven't been doing part contracts (or contracts at all), but those requirements seem to be in line with the speeds you'll get when launching something into orbit. At best, you may need to slow down a bit by cutting on throttle.

So just launch whatever payload you want to launch for whatever purpose you want to launch, make sure you're using an LV-T45 to launch it and you should meet those requirements during ascend.

[Spricigo]

41 minutes ago, juanml82 said:

I've been playing science career for several months, so I haven't been doing part contracts (or contracts at all), but those requirements seem to be in line with the speeds you'll get when launching something into orbit. At best, you may need to slow down a bit by cutting on throttle.

1km/s at 40km is a tad slow for me. At that altitude I'd like to be almost at orbital speed if I can.

In any case a valid suggestion, just instead of cutting throttle is probably better to  just follow a trajectory that is initially more vertical t(to gain altitude more quickly) and turn more sharply later on. Cosine losses will increase but, hopefully, gravity losses not so much.