SS2 engine performance improvement

[kook59]

Just wondering why SS2 doesn't use a bigger nozzle. One of the advantages of air launch is the low pressure at altitude allowing a vacuum optimized nozzle for better ISP. Maybe spice up the fuel grain with some aluminum powder for more energy?
Thoughts

[kook59]

For the rocket scientists: how much more performance is needed to reach 100km with a full load?

[darkenfast]

For the rocket scientists: how much more performance is needed to reach 100km with a full load?

The February 2019 and May 2021 flights of SpaceShipTwo approached altitudes of 90 km, so it's possible that the few remaining test flights of SpaceShipTwo will pass the 100 km threshold and reach a speed of Mach 3.3. SpaceShipThree is a slightly upgraded performance version of SpaceShipTwo, so it probably has a maximum altitude of 120 km and Mach 3.5, even though the Spaceship Company has yet to publicly release projected specs for SpaceShipThree.

Until you can provide some evidence for these improvements in SpaceShipTwo's performance, they remain imaginary numbers.

[Kryten]

For the rocket scientists: how much more performance is needed to reach 100km with a full load?

The February 2019 and May 2021 flights of SpaceShipTwo approached altitudes of 90 km, so it's possible that the few remaining test flights of SpaceShipTwo will pass the 100 km threshold and reach a speed of Mach 3.3. SpaceShipThree is a slightly upgraded performance version of SpaceShipTwo, so it probably has a maximum altitude of 120 km and Mach 3.5, even though the Spaceship Company has yet to publicly release projected specs for SpaceShipThree.

I haven't seen any statement from VG that SS3 has improved performance, only operations and manufacturability improvements.

[ncb1397]

For the rocket scientists: how much more performance is needed to reach 100km with a full load?

The February 2019 and May 2021 flights of SpaceShipTwo approached altitudes of 90 km, so it's possible that the few remaining test flights of SpaceShipTwo will pass the 100 km threshold and reach a speed of Mach 3.3. SpaceShipThree is a slightly upgraded performance version of SpaceShipTwo, so it probably has a maximum altitude of 120 km and Mach 3.5, even though the Spaceship Company has yet to publicly release projected specs for SpaceShipThree.

I haven't seen any statement from VG that SS3 has improved performance, only operations and manufacturability improvements.

scroll to 1:30....

[trimeta]

For the rocket scientists: how much more performance is needed to reach 100km with a full load?

The February 2019 and May 2021 flights of SpaceShipTwo approached altitudes of 90 km, so it's possible that the few remaining test flights of SpaceShipTwo will pass the 100 km threshold and reach a speed of Mach 3.3. SpaceShipThree is a slightly upgraded performance version of SpaceShipTwo, so it probably has a maximum altitude of 120 km and Mach 3.5, even though the Spaceship Company has yet to publicly release projected specs for SpaceShipThree.

I haven't seen any statement from VG that SS3 has improved performance, only operations and manufacturability improvements.

scroll to 1:30....

The only performance improvement mentioned is "it's lighter" (which of course has nothing to do with the engines being more powerful). Considering that in the past it's carried at most three people, but the nominal passenger complement is six, it's not necessarily clear that the weight reduction even offsets the extra people, let alone affords additional capabilities.

[gaballard]

It's lighter, okay, but have they solved those pesky "airframe starts to come apart after a single use" issues?

[Robotbeat]

Just wondering why SS2 doesn't use a bigger nozzle. One of the advantages of air launch is the low pressure at altitude allowing a vacuum optimized nozzle for better ISP. Maybe spice up the fuel grain with some aluminum powder for more energy?
Thoughts

The nozzle is already optimized for high altitude.

[wannamoonbase]

It's lighter, okay, but have they solved those pesky "airframe starts to come apart after a single use" issues?

That’s an ignorant comment.  Frankly rude too, a test pilot died.  They fixed that issue and have retested for years.  They are going to be fine. 

[AC in NC]

It's lighter, okay, but have they solved those pesky "airframe starts to come apart after a single use" issues?

That’s an ignorant comment.  Frankly rude too, a test pilot died.  They fixed that issue and have retested for years.  They are going to be fine.

I could be wrong but I don't think he was referring to the accident which as I recall was caused by human error not airframe resiliency.

[Comga]

For the rocket scientists: how much more performance is needed to reach 100km with a full load?

To get from the 86.2 km apogee to 100 km would take an additional 520 m/s
At 3 g's that would be around 18 seconds over the nominal 60 second burn
No idea if there is that much fuel or oxidizer.
Have they done a longer burn than 60 sec or even tested an engine for 78 seconds?
Then there would be the issues of the half kilometer per second faster atmospheric entry and the increased structural stresses.
But the hybrid rocket might be able to show one of its (few) advantages in being able to throttle to limit the acceleration.
(Do the controls throttle the SS2 engine or just turn it on and shut it off?)

At apogee, the velocity was shown as 674 mph.
(Gotta love those Imperial units!)
(No idea why it's important to keep that much horizontal velocity.)
If the direction was stills straight up, it would have risen another 4.63 km to almost 91.km
To get from there to  100 km is "only" 424 m/s or 14 seconds at 3 g's.

[meekGee]

It's lighter, okay, but have they solved those pesky "airframe starts to come apart after a single use" issues?

That’s an ignorant comment.  Frankly rude too, a test pilot died.  They fixed that issue and have retested for years.  They are going to be fine.

Slow down, he's talking about the current issue, not the one involved in the accident.

And I am not sure that thet have, I think rn they're just monitoring it.

[trimeta]

But the hybrid rocket might be able to show one of its (few) advantages in being able to throttle to limit the acceleration.
(Do the controls throttle the SS2 engine or just turn it on and shut it off?)

According to Tim Dodd's latest video/article comparing SpaceShipTwo with New Shepard, RocketMotorTwo cannot throttle, it's either on or off. I'm not sure specifically where he got that info from.

[nacnud]

Apparently the ISP goes to pot if you try to throttle a hybrid motor.

Interestingly I also discovered that RocketMotorTwo seems to be about the same thrust as NewtonThree from virgin orbital. 310kN vs 330kN