Recent content by jkn

"NASA has certified the current version of the SpaceX Falcon 9 to launch some categories of science missions" If I have understood correctly SpaceX is not producing 'current version' any more. NASA's certification process is too slow or SpaceX development speed too high.

I don't think I have called Amos 6 as a launch failure. I know my English is bad, but I am careful with key words. I will be calling it failure or failure while preparing for launch. They were doing that. If title is 'launch failures' then you could exclude Amos 6. That is not a stat...

No I didn't. I don't know much about manufacturing. So I'll try to compare how complex products are. I think Elon said 10* production rate cut productions costs to half. That makes sense, but rocket production rate is too low. If they are limited by fairing production, then I go back to my...

6 M$ for fairing makes it roughly as expensive as 2.stage. Merlin must be much cheaper than 6 M$, because F9 has 10 Merlins. So I have trouble understanding fairing price. I found support for my ideas: Cost calculation for Falcon 9 & Falcon Heavy • r/spacex

Amos 6 failure happened during preparation for launch not during launch. If I'm hired to move a piano and I break it while backing it for transport, I should not explain to client that I did not broke it during transport. You can draw a line between preparation for launch and launch, but I'll...

As I understand this: Precession rate depends on altitude. Change of altitude will change orbital plane relative to satellites on different altitude. Those satellites must have large batteries for operation on night side. So ion-drives could be used on night side also. I think I could...

Acceleration (trust) of ion drive is limited by available power. These satellites might have rather large solar panels anyway. Dawn used ion drive about 2.5 AU from the Sun. Earth gets 6 times as much solar energy. LEO satellite is on shadow half of the time, so only 3*. With ion drive...

I think they have 2 failures, because they have lost main cargo twice. 25 launches without issues is a reason to celebrate.

I don't see large calculation errors (didn't check small ones:) Are you planning 2. stage with larger propellant tanks? I don't think SpaceX will do it, because launch cost of BFR should be smaller than launch cost of F9. I think they should copy ion drive from Dawn Mission | Mission...

After thinking this (and sleeping), I decided my first idea is correct. Change of orbital plane requires change in direction of velocity even if inclination is same. Doing that with v=sqrt(earthmass*G/(1150 km + earthradius)) = 7.281 km / s is difficult. This makes BFR less efficient in...

My first thought: No, it takes too much delta-v to change between LEO orbital planes. Fully reusable F9 would be good. Before posting I thought again: Inclination is same, so perhaps delta-v is not too high. At least if you have time. LEO constellation has 5 different inclinations and VLEO...

I did read Technical Attachment:) "Each satellite in the SpaceX System is designed for a useful lifetime of 5 to 7 years." So they need to get them to orbit in less than 5 years. LEO constellation has 83 orbital planes, so 83 launches is needed, more for 7518 VLEO satellites. VLEO is low...

Extinction causing asteroids are rare. Planet sterilizing even more rare. But city killer size asteroids come once in 100 - 200 years. For example Tunguska event - Wikipedia was about 1000 times more powerful than nuclear bomb dropped to Hiroshima. It would be very useful to detect these...

Of course there is. My purpose was to find order of magnitude. So what is wrong with this: Last change to orbit was made close to Earth, so orbits of Roadster and Earth will intersect on that point. Earth moves its own diameter in less that 7 minutes -> 7 min/year = 1.3e-05 In 100 000 years...

I agree, but I still think 2. stage is much more complex. Aerodynamic forces attacking fairing will be passed to 2. stage. It also has a rocket engine. Fraser Cain claims: Each RS-25 probably cost NASA around 60 M$. SLS uses 4 of those.