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US Space Force reveals first look at secretive X-37B space plane in orbit

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Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#71

Post by xattt »

everfrustrated wrote: post #64
justahuman74 wrote: post #33

Earlier quoted context omitted.

My orbital mechanics is (like most people) weak, is this intended as a generalized physical threat to other satellites?

Not necessarily. These types of orbits also have the property that the perceived loiter time is different for the perigee and apogee. At perigee (closest to Earth) it will be moving very fast and so any changes to velocity will have a large impact (easily change orbit). While at apogee it will appear to sit in space and move quite slowly. As an example this is used for the Russian GPS system so their satellites can s…

Isn’t GLONASS in geostationary orbit like NAVSTAR/GPS? This would be a fixed orbital distance from Earth.

You may be thinking of highly-elliptical molniya/lightning orbits (1), which enabled state TV broadcasts for high-lat places in Siberia.

(1) https://en.m.wikipedia.org/wiki/Molniya_orbit

Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#72

Post by xattt »

brylie wrote: post #69
appointment wrote: post #60

Earlier quoted context omitted.

This flight was launched with a Falcon Heavy, that is why it has more energy to reach high orbit than the previous launches with an Atlas V booster. When you are in a highly eccentric orbit (meaning the point in the orbit farthest from Earth (apogee) is much higher than the lowest point (perigee)) like this one there are several maneuvers you can do to significantly change your orbit with relatively little energy. Th…

Thanks for the great response! It's been a while since I played KSP, and I completely forgot about the apoapsis maneuvers :-) As an aside, it's sad about KSP2. We need a good, open-source space simulator in the spirit of KSP, which has incredible enthusiasm in the modding community.

I can imagine there are folks that do their day job at the Space Force and come home to load up KSP to blow off some steam.

Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#73

Post by exDM69 »

roelschroeven wrote: post #67
exDM69 wrote: post #40

Earlier quoted context omitted.

Burns at perigee have best efficiency to make in-plane changes (raise or lower orbit) due to the Oberth effect. Burns at apogee have best efficiency for out-of-plane maneuvers (change orbital inclination plane) due to lowest velocity of the spacecraft. Highly elliptical orbits can do both at a few hours' notice.

Burns at perigee can only raise or lower part of the orbit though, right? A burn at perigee lowers or raises the apogee. To lower or raise the perigee, you need to burn at apogee.

Correct.

Burns don't have to happen only at perigee/apogee so there's more flexibility in practice. And counter intuitive stuff like bi-elliptic transfers.

Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#74

Post by euroderf »

dredmorbius wrote: post #35
nxobject wrote: post #17

Given the military heritage of the Space Shuttle, I imagine this is what a hypothetical next generation civilian Space Shuttle might have looked like, too.

Given the constraints of reaching orbit, surviving reentry, and cross-range capabilities there's a general lack of variability in spacecraft design. Some of us are old enough to remember promotional/propaganda materials concerning the original Boeing X-20 "Dyna-Soar" engineering designs from the 1950s which strongly resemble the subsequent US Space Shuttle, the Soviet Buran orbiter, and the Boeing X-37B and X-40: htt…

I recall reading that the Space Shuttle was a big improvement on Dynasoar. Perhaps that the Dynasoar was not a true "lifting body" ?

Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#76

Post by credit_guy »

rich_sasha wrote: post #46
dylan604 wrote: post #34

Earlier quoted context omitted.

This thing is definitely out of SAM range, so that's an advantage.

I was going to say, not out of range of anti-satellite missiles, at least at a low perigee... But maybe it's zipping too fast there to be easily shot down? Whereas at apogee, when it's slow, it's also very far away.

> But maybe it's zipping too fast there to be easily shot down?

A satellite in LEO already has a speed of about 8 km/s. The highest speed of a satellite in a highly elliptical orbit is 11 km/s. It you can shoot a satellite at 8 km/s, you probably can also shoot it at 11 km/s.

The problem is, of course, that the perigee of a satellite in a highly elliptical orbit can be over a different part of the planet than your SAM battery.

Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#77

Post by rcxdude »

xattt wrote: post #71
everfrustrated wrote: post #64

Earlier quoted context omitted.

Not necessarily. These types of orbits also have the property that the perceived loiter time is different for the perigee and apogee. At perigee (closest to Earth) it will be moving very fast and so any changes to velocity will have a large impact (easily change orbit). While at apogee it will appear to sit in space and move quite slowly. As an example this is used for the Russian GPS system so their satellites can s…

Isn’t GLONASS in geostationary orbit like NAVSTAR/GPS? This would be a fixed orbital distance from Earth. You may be thinking of highly-elliptical molniya/lightning orbits (1), which enabled state TV broadcasts for high-lat places in Siberia. (1) https://en.m.wikipedia.org/wiki/Molniya_orbit

Gps isn't in geostationary orbit. They're in medium earth orbit and complete an orbit about twice a day

Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#78

Post by dylan604 »

Earw0rm wrote: post #53
dylan604 wrote: post #37

Earlier quoted context omitted.

The NRO doesn't need this thing to lift its birds into orbit. Keyhole satellites have gotten rides on Deltas and Titans, so probably going to be sticking their thumbs out in the direction of SpaceX pretty soon.

Already have, SpaceX have been doing a few NRO launches. Delta and Titan are retired, and Atlas is down to its last few.

Great, but I specifically said Keyhole from which Hubble was a descendant. Which Keyhole bird was launched by SpaceX?

Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#79

Post by inejge »

everfrustrated wrote: post #64
justahuman74 wrote: post #33

Earlier quoted context omitted.

My orbital mechanics is (like most people) weak, is this intended as a generalized physical threat to other satellites?

Not necessarily. These types of orbits also have the property that the perceived loiter time is different for the perigee and apogee. At perigee (closest to Earth) it will be moving very fast and so any changes to velocity will have a large impact (easily change orbit). While at apogee it will appear to sit in space and move quite slowly. As an example this is used for the Russian GPS system so their satellites can s…

As an example this is used for the Russian GPS system so their satellites can sit in high earth latitudes for longer needing fewer satellites to cover Russia.

It's used for communications satellites and is called the Molniya orbit[1]. Their GLONASS (positioning system) satellites use circular medium altitude orbits, but with a higher inclination (about 65 deg vs. GPS's 55 deg).

[1] https://en.wikipedia.org/wiki/Molniya_orbit

Re: US Space Force reveals first look at secretive X-37B space plane in orbit

#80

Post by tliltocatl »

jl6 wrote: post #61
DoingIsLearning wrote: post #57

Earlier quoted context omitted.

Interact as in fly-by repair? Or interact as in interfere/tamper/destroy?

Looks like it would be able to deploy high speed instant-action repair kits.

Unlikely, velocity difference would be too large for anything constructive. One thing about orbits is that velocity difference is sort of a distance dimension in itself.
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