Star Orbiter G80T...Supersonic?

[ebman159]

Just remember, mass is your enemy when looking for max velocity. Not necessarily so when attempting max altitude..In other words, keep it light..

Oh yes.... Trying to lighten it up while keeping it sturdy, fast and sleek. Im hoping to launch within the next 2-3 weeks. I’m on vacation currently lol!

 

[kuririn]

FWIW an OR sim with an Estes G80 shows .89 Mach.
With an AT G138T it sims at 1.12 Mach.
Either way, you would not know if it went supersonic without electronics, which would add some incremental weight.
Any sonic boom produced likely would not be audible from the ground.
So an H or high power G would be the way to go, but they require an L1 cert. to buy.
BTW I used the Rocksim file at EMRR.
And Open Rocket runs both .ork and .rkt files, and it's free.
Cheers.

 

[ebman159]

FWIW an OR sim with an Estes G80 shows .89 Mach.
With an AT G138T it sims at 1.12 Mach.
Either way, you would not know if it went supersonic without electronics, which would add some incremental weight.
Any sonic boom produced likely would not be audible from the ground.
So an H or high power G would be the way to go, but they require an L1 cert. to buy.
BTW I used the Rocksim file at EMRR.
And Open Rocket runs both .ork and .rkt files, and it's free.
Cheers.

Think with modification I could nudge it into mach1?

 

[kuririn]

You can try mods to reduce weight. The conundrum is you also want to beef it up to survive going supersonic, which will add weight. Plus there is the weight of the electronics.
Biggest problem is the cross section. You want to go minimum diameter to go faster.
A G80 on an Apogee Aspire will get you to Mach 1.12
And almost 3300 ft. apogee.
You will need a good set of eyes to get it back.
Laters.

 

[ebman159]

You can try mods to reduce weight. The conundrum is you also want to beef it up to survive going supersonic, which will add weight. Plus there is the weight of the electronics.
Biggest problem is the cross section. You want to go minimum diameter to go faster.
A G80 on an Apogee Aspire will get you to Mach 1.12
And almost 3300 ft. apogee.
You will need a good set of eyes to get it back.
Laters.

Thank you. Strongly appreciate the information!!!

 

[ebman159]

Anyone know what would happen if shorten the total length of the rocket..? By a little? By a lot?

 

[Theory]

Anyone know what would happen if shorten the total length of the rocket..? By a little? By a lot?

The Cp / Cg will move. How much? OpenRocket knows

 

[Wallace]

Virtually everything is a trade off. Play with the #'s and see what you can come up with..

 

[ebman159]

Got this design so far, it goes Mach 1.02 according to the simulations, although it doesn't even look like a star orbiter anymore. However I am using most of the parts as they are cheap, readily available, and technically still meet my standards for my goal. My goal was to modify a star orbiter kit to go supersonic speeds with a G80T engine. I am new to rocket design so please let me know if you see any faults, errors, weaknesses, etc. This is kindof short for a supersonic rocket, and it seems unstable but I don't the stability needs to be very high as long as the rocket maintains it's small design.

 

[dhbarr]

I believe you'll find this design unstable as the CP has a tendency to move forward in the transonic region.

So you would expect it to boost off the pad quite quickly but destabilize at around m0.8 or so, then immediately turn to confetti.

 

[ebman159]

I believe you'll find this design unstable as the CP has a tendency to move forward in the transonic region.

So you would expect it to boost off the pad quite quickly but destabilize at around m0.8 or so, then immediately turn to confetti.

 

[ebman159]

I believe you'll find this design unstable as the CP has a tendency to move forward in the transonic region.

So you would expect it to boost off the pad quite quickly but destabilize at around m0.8 or so, then immediately turn to confetti.

Alright but in all seriousness...if I got the cal/stability up to 1, would that be ideal? I mean I wasn't expecting the stability to be too high due to it being such a small rocket, but you make a good point about the CP. What stability should I shoot for?

 

[Wallace]

Do a plot in Open Rocket, it'll show you CP shift, it's a dynamic rather than static "thing". Try a sim without the launch lugs , maybe with an F50 in lieu of the G80 , and see what changes, sims are cheap and easy, they're pretty draggy. Assuming that rectangle in the forward BT is electronics? I'd move them into the nose cone as far forward as possible. A chute shelf might also be in order and move that motor forward. Friction fit seems to be the lightest method of retainment so I'd suggest looking into it. Looks to me like you have some good ideas, they just need some fine tuning. Try working with the mass you have in order to avoid adding more. And don't forget potential landing damage...

 

[Theory]

that fin shape may have some issues in transonic / mach flight

i would run them through fin-sim them to ensure they (built in the material of your choice) hold up.

 

[Wallace]

that fin shape may have some issues in transonic / mach flight

i would run them through fin-sim them to ensure they (built in the material of your choice) hold up.

Does anyone know if Fin Sim is still available? I've attempted contact more than once without result.

 

[ebman159]

that fin shape may have some issues in transonic / mach flight

i would run them through fin-sim them to ensure they (built in the material of your choice) hold up.

I have designed like five or six versions of this rocket that all have different stabilities and wing designs. I’m going to test all of them in sims and see what happens. I stayed up until like 4 am designing lol.

Do a plot in Open Rocket, it'll show you CP shift, it's a dynamic rather than static "thing". Try a sim without the launch lugs , maybe with an F50 in lieu of the G80 , and see what changes, sims are cheap and easy, they're pretty draggy. Assuming that rectangle in the forward BT is electronics? I'd move them into the nose cone as far forward as possible. A chute shelf might also be in order and move that motor forward. Friction fit seems to be the lightest method of retainment so I'd suggest looking into it. Looks to me like you have some good ideas, they just need some fine tuning. Try working with the mass you have in order to avoid adding more. And don't forget potential landing damage...

I did a CP and CG plot and compared it relative to the velocity...it seems that the CP doesn't change much. The CG starts at 45.5 and the CP at 48.8. They steadily rise and even after they surpass the speed of sound, not much changes, the CP steadily rises and the CG behaves as it would. I thought the CP would drastically change after surpassing the speed of sound?

Long story short I think it means the rocket is stable throughout the flight. The CP is always a higher number than the CG. That means its stable right? Again I don't know, I'm kindof new to this rocket design thing.

 

[ebman159]

Here is the design I am most confident in. It is more stable than the first and the winds are a little more sturdy I believe. I was told basswood is a good wing material for supersonic while remaining lightweight?

 

[ebman159]

Here is a higher stability design, but slower. And i think the wings would definitely break of with this design. Just throwing crap out there, you guys know more than I do!

 

[Nytrunner]

I was told basswood is a good wing material for supersonic while remaining lightweight?

I'll clarify what I said:
-I said replacing the fins of the Star Orbiter (as in the original fin shape) with basswood would be stronger than balsa.
The Star Orbiter has a good fin design. Triangular (delta) with large root for strength, and is a shape that is decent for high speeds (It's span/height is a little long).
(see below shape of fins for a Mach 2+ rocket)

The fins you're proposing are very thin and swept so far back that they're twisting unsupported by the root (especially that 3rd design)
Fiberglass or carbon fiber could get away with your first design at those speeds.

 

[ebman159]

I'll clarify what I said:
-I said replacing the fins of the Star Orbiter (as in the original fin shape) with basswood would be stronger than balsa.
The Star Orbiter has a good fin design. Triangular (delta) with large root for strength, and is a shape that is decent for high speeds (It's span/height is a little long).
(see below shape of fins for a Mach 2+ rocket)

The fins you're proposing are very thin and swept so far back that they're twisting unsupported by the root (especially that 3rd design)
Fiberglass or carbon fiber could get away with your first design at those speeds.

Ahhhh I gotcha. That makes a ton of sense. I’ll plug in carbon fiber or fiberglass to the sims and see what I get...are there any lighter materials that would work...? Thank you for the info!

 

[ebman159]

Would basswood fins with a carbon fiber of fiberglass shell work? I think it’d help reduce weight while still retaining some strength from the stronger materials.

 

[ebman159]

Would basswood fins with a carbon fiber of fiberglass shell work? I think it’d help reduce weight while still retaining some strength from the stronger materials.

I’ve heard of people going supersonic on CA and epoxy strengthened balsa....idk if it’s teue but I’ll experiment with a few things and see

 

[Nytrunner]

Even putting adhesive label paper over the fins will increase their strength.
Laminating CF or fiberglass will definitely add more weight.

You're discovering the Lightweight vs Survivable at Speed issue now.

Whatever you do, keep experimenting, and keep reading. You may have to fly a couple test rockets with an altimeter and discover exactly how they perform (and what the sims Don't tell you).

 

[ebman159]

Even putting adhesive label paper over the fins will increase their strength.
Laminating CF or fiberglass will definitely add more weight.

You're discovering the Lightweight vs Survivable at Speed issue now.

Whatever you do, keep experimenting, and keep reading. You may have to fly a couple test rockets with an altimeter and discover exactly how they perform (and what the sims Don't tell you).

Yep. Gonna try strengthening the basswood that I already have and see what happens. If I need new materials I’ll see what happens. Thank you for the useful info.

 

[ebman159]

I have designed like five or six versions of this rocket that all have different stabilities and wing designs. I’m going to test all of them in sims and see what happens. I stayed up until like 4 am designing lol.

I did a CP and CG plot and compared it relative to the velocity...it seems that the CP doesn't change much. The CG starts at 45.5 and the CP at 48.8. They steadily rise and even after they surpass the speed of sound, not much changes, the CP steadily rises and the CG behaves as it would. I thought the CP would drastically change after surpassing the speed of sound?

Long story short I think it means the rocket is stable throughout the flight. The CP is always a higher number than the CG. That means its stable right? Again I don't know, I'm kindof new to this rocket design thing.

Also again, if someone could translate my CP and CG confusion here that’d be cool. I just expected the CP to have a more drastic change in the transonic range rather than just continual steady change...maybe I’m wrong?

 

[Wallace]

Open Rocket is normally pretty close...As long as you feed it good info. I know I've been guilty of bad input more than once, usually due to hurried conditions. Post flight "tuning" of sims almost always matches altimeter data way closer than I'd have thought possible.

 

[ebman159]

Open Rocket is normally pretty close...As long as you feed it good info. I know I've been guilty of bad input more than once, usually due to hurried conditions. Post flight "tuning" of sims almost always matches altimeter data way closer than I'd have thought possible.

Well that’s good to know...I think my rocket might actually work but I don’t wanna speak too soon. I’ve spend at least 12-15 hours running designs and sims with specific data. I suppose I won’t know for sure until I try! Thank you all for the help and I’ll keep you posted.

 

[Nytrunner]

I’ve spend at least 12-15 hours running designs and sims with specific data. I suppose I won’t know for sure until I try!

This is truth. Test flights can reveal things you never knew, and prove/disprove assumptions you didn't know you made.

 

[ebman159]

So I’ve collected everything and I’ve been sanding my fins after CA hardnening for the last week. They’re finally polished. I just put them on the body tonight. I was surprised how strong those fins were after hardening. I’m going to paint the body and polish, But the whole thing is coming together and we’re looking at launching on August 18th. I’ll keep y’all posted.

 

[Nytrunner]

How much does it weigh?