6 ms·
IANARS but this plane should give the remaining stage(s) four advantages: 1. +230m/s orbital velocity [1] 2. +9km launch altitude [1] 3. can launch in more w
by mLuby 9y ago
IANARS but this plane should give the remaining stage(s) four advantages:
1. +230m/s orbital velocity [1]
2. +9km launch altitude [1]
3. can launch in more weather conditions
4. 1st stage can abort mid-launch without loss of payload.
Of these, the most important is the increase in launch altitude, because that means stage 2 launches in air of greatly decreased density, leading to the following efficiencies:
A. a vacuum-optimized nozzle can be used, increasing engine performance
B. less aerodynamic/drag energy losses
C. max Q should be lower, allowing full throttle usage, reducing mass needed for structural elements, and reducing vibration stresses on payload
[1] http://dailym.ai/2soH6FD http://dailym.ai/2soH6FD
P.S. Thank you KSP for teaching me this stuff! :D
Bonus: video of pegasus air launched rocket: https://www.youtube.com/watch?v=jz_5hnIw2jc https://www.youtube.com/watch?v=jz_5hnIw2jc
- guscost 9y agoNeat - I kind of intuitively knew about B. from playing KSP, but the other two are interesting.
- Gravityloss 9y agoYou can also fly towards the equator before the launch for more boost. Further from the Earth's axis. For example Cape Kennedy is 28 degrees north. If you fly to the equator, you get another 200 m/s. Depends a bit to which orbit you're launching though. Another good thing is flexibility if you are more constrained by launch windows in a stationary launch location. Hard to explain.
- Gravityloss 9y agoI had a big mistake in the comment above, it's 220 km/h or about 60 m/s. cos(28)=0.88 0.12*(2*pi*7000 km) = 5300 km 5300 km / 24 h = 220 km/h 220 km/h / 3.6 m/s/km/h = 61 m/s
- jameshart 9y agoIs 4. really doable? Would have thought landing while carrying a fully fueled rocket might be pretty high risk.
- mLuby 9y agoI haven't actually seen anyone mention it, but it shouldn't be much more risky than taking off fully-fueled. That said, landing with the rocket still on board might break some fuel-balancing assumptions.
- gernerz 9y agoPeagus rockets aren't cryogenic, they are solid monopropellant rockets. Not really all that dangerous.
- tacticus 9y agoLanding weights are usually a bit lower than take off weights due to the extra shock on landing. for example the a340-600 has a MTOW of 380 tons but a Max landing weight of 265 tons. Just a bit of a difference.
- rbanffy 9y agoThat's the fuel the plane takes off with. I don't know how much this beast uses, but those six engines must be burning quite a lot of it. Also, the landing gears seem to be very robust.
- 9y ago
- iijj 9y agoThe primary advantage of airplane launch is that you can fly to into a launch window for an orbital rendezvous. Otherwise you'd have to wait for the target's orbit to be just right w/respect to the launch site, or do a long orbit matching process. This is very useful if say you want to very quickly and quietly launch something towards another satellite. People are making comparisons with the Spruce Goose, but the Glomar Explorer may be a better analogy.
- 205guy 9y agoLooks more like the Pineering Spirit, a ship made from 2 hulls side by side: https://en.wikipedia.org/wiki/Pioneering_Spirit_(ship) https://en.wikipedia.org/wiki/Pioneering_Spirit_(ship) There are videos of this thing lifting an entire oil platform at once.
- Retric 9y agoThe largest downside is the rocket needs to be strong in more than one direction which adds a lot of weight. Sub Mach 1 first stage will save a little net weight but significantly less than you might diets assume.
- CydeWeys 9y agoSure, but the strength it needs to have in the additional "hanging horizontal" orientation is only 1g -- much less than the many-g strength that all rockets need to have along their thrust axis. It adds some weight, but not enough to ruin the other benefits.
- robbiep 9y agoThe spruce Goose analogy comes from wingspan, which is directly from the article
- kevin_thibedeau 9y agoHe's hinting that this is a black program with a fake public cover story.
- credit_guy 9y agoAvoiding drag could be a huge benefit if you envision an air breathing second stage (ramjet or scramjet).