Having a hard time getting an unmanned rocket to fly straight.

[[GFL] The Unkindled One]

I've got the (Sputnik-like) sattelite mounted safely. There are no options for a person to fly the craft, I've got the flight systems installed. When I exit the first stage of lift-off(usually a solid fuel rocket which gives way to a liquid fuel rocket) the craft careens and sways wildly. What am I doing wrong?

[sal_vager]

It's hard to tell without seeing the craft, but don't forget that the Stayputnik doesn't have SAS, if you have a SAS probe you could fit that as well.

You'll likely want fins on the liquid stage to help with stability, if they are only on the SRB they'll be lost when you stage.

Something that people often forget, like an arrow or a dart a rocket needs some mass at the front, if you add a FL-T100 and disable its fuel flow until you need it it'll add some mass and help prevent the craft from wanting to fly backwards.

[[GFL] The Unkindled One]

Originally posted by sal_vager:

It's hard to tell without seeing the craft, but don't forget that the Stayputnik doesn't have SAS, if you have a SAS probe you could fit that as well.

You'll likely want fins on the liquid stage to help with stability, if they are only on the SRB they'll be lost when you stage.

Something that people often forget, like an arrow or a dart a rocket needs some mass at the front, if you add a FL-T100 and disable its fuel flow until you need it it'll add some mass and help prevent the craft from wanting to fly backwards.

I've added an SAS module and everything, not sure why the second stage screws it up

[George Kerman]

Where exactly (at which altitude) do you decouple the SRB? For example, a Stayputnik (your probe), a FLT-400, a Terrier with a "Thumper" SRB can go interplanetary with no issues. That's because of the awesomeness of the Thumper that can bring your terrier higher than 25 km where the atmosphere is an insignificant factor.

You don't need fins or anything else, just these 4 parts and maybe 2 small batteries mounted on the probe. That's it (for this model)

[[GFL] The Unkindled One]

Originally posted by George Kerman:

Where exactly (at which altitude) do you decouple the SRB? For example, a Stayputnik (your probe), a FLT-400, a Terrier with a "Thumper" SRB can go interplanetary with no issues. That's because of the awesomeness of the Thumper that can bring your terrier higher than 25 km where the atmosphere is an insignificant factor.

I run out of fuel and momentum around 6,000 meters, and then I activate my 2nd stage. Tends to go haywire and is a chore to regain control. I personally think the issue lies in the size restrictions I have to work around. I'm restricted to an 18 tonne launch pad and a 30 part rocket. The sattelite itself, consisting of StayPutNick, SAS module, Comms Dish, Solar Panel, and protective cone consists of 8 pieces in total. So what am I doing wrong in terms of design?

[George Kerman]

Dude, wtf, 6000m. It's not a good place to do things without SAS.

For example, this:


http://steamcommunity.com/sharedfiles/filedetails/?id=875376530

can go interplanetary, as you can see from the dV readings.

You could add maybe two of those small relay antennas and some solar panels, wouldn't change much.

Do you want me to show you a test flight?

[Toastie Buns]

Originally posted by GFL The Unkindled One:

Originally posted by George Kerman:

Where exactly (at which altitude) do you decouple the SRB? For example, a Stayputnik (your probe), a FLT-400, a Terrier with a "Thumper" SRB can go interplanetary with no issues. That's because of the awesomeness of the Thumper that can bring your terrier higher than 25 km where the atmosphere is an insignificant factor.

I run out of fuel and momentum around 6,000 meters, and then I activate my 2nd stage. Tends to go haywire and is a chore to regain control. I personally think the issue lies in the size restrictions I have to work around. I'm restricted to an 18 tonne launch pad and a 30 part rocket. The sattelite itself, consisting of StayPutNick, SAS module, Comms Dish, Solar Panel, and protective cone consists of 8 pieces in total. So what am I doing wrong in terms of design?

Take Sal's advice and slap some fins on there. Fins will insure your centre of pressure remains below the craft, which gives it more hang time before it flips violently.

It's by no means perfect and you should probably redesign your craft, but it will allow you to 'wing' (teeheehee) some flights you just can't be bothered to redesign, especially if they're silly to begin with.