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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

#101

Post by jjk166 »

s1artibartfast wrote: post #98
credit_guy wrote: post #97

Earlier quoted context omitted.

That's not quite correct, is it? Consider shooting at a bird. A falcon travels twice as fast as a pigeon, but you don't need a bullet that is twice as fast to shot the falcon. You simply adjust the lead distance when you shoot at the falcon. In your argument you assume that you need to cover some distance in the same amount of time, but you don't need to. You simply lead the target a bit more. As for detection time,…

Agreed, it all depends on the use case. If you are trying to hit an evading target, you have to be faster. If you are trying to deny the ship from a destination, you don't.

If the ship's current position is 200 miles from its destination and you are 400 miles from its destination, you need to go faster than it to deny the ship from its destination. Conversely, if you are 40 miles from its destination, you can go much slower, though if you go too slow you still won't make it. You have to get to a point ahead of it before it gets there, and the faster its moving, the less time you have available to get to any particular point.

Dealing with evasion is a whole other matter. A stationary iceberg can hit a ship that tries to evade if it does so too late. Conversely simple error in your knowledge of a ship's position and velocity can cause it to be miles away from where you expect it later in the journey.

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

#102

Post by monkeyfun »

exDM69 wrote: post #73
roelschroeven wrote: post #67

Earlier quoted context omitted.

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.

Ahhhh, bi-elliptic transfers!

It's funny, I remember first learning to use such arcane maneuvers in a game called Children of a Dead Earth, in order to get into a terribly low orbit of Neptune to strike a methane refinery... My poor brain was always used to simple Hohmann transfers in games like KSP!

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

#103

Post by s1artibartfast »

jjk166 wrote: post #101
s1artibartfast wrote: post #98

Earlier quoted context omitted.

Agreed, it all depends on the use case. If you are trying to hit an evading target, you have to be faster. If you are trying to deny the ship from a destination, you don't.

If the ship's current position is 200 miles from its destination and you are 400 miles from its destination, you need to go faster than it to deny the ship from its destination. Conversely, if you are 40 miles from its destination, you can go much slower, though if you go too slow you still won't make it. You have to get to a point ahead of it before it gets there, and the faster its moving, the less time you have av…

Like the parent says, you already know where it is. I'm struggling to understand the case where you are further from the destination than the x37B, with an orbit 60,000km from earth.

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

#104

Post by jjk166 »

s1artibartfast wrote: post #103
jjk166 wrote: post #101

Earlier quoted context omitted.

If the ship's current position is 200 miles from its destination and you are 400 miles from its destination, you need to go faster than it to deny the ship from its destination. Conversely, if you are 40 miles from its destination, you can go much slower, though if you go too slow you still won't make it. You have to get to a point ahead of it before it gets there, and the faster its moving, the less time you have av…

Like the parent says, you already know where it is. I'm struggling to understand the case where you are further from the destination than the x37B, with an orbit 60,000km from earth.

> Like the parent says, you already know where it is.

The parent is incorrect. You know approximately where it is. If your approximation is off by some amount, you miss. How good of an approximation you have is determined by your detection equipment. How good of an approximation you need is determined by the speed. For the same detection equipment, hitting the faster moving thing is harder.

> I'm struggling to understand the case where you are further from the destination than the x37B, with an orbit 60,000km from earth.

Well yeah, that's because the x37B interception scenario is the second case, where you are much closer to the destination but going much slower.

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

#105

Post by s1artibartfast »

jjk166 wrote: post #104
s1artibartfast wrote: post #103

Earlier quoted context omitted.

Like the parent says, you already know where it is. I'm struggling to understand the case where you are further from the destination than the x37B, with an orbit 60,000km from earth.

> Like the parent says, you already know where it is. The parent is incorrect. You know approximately where it is. If your approximation is off by some amount, you miss. How good of an approximation you have is determined by your detection equipment. How good of an approximation you need is determined by the speed. For the same detection equipment, hitting the faster moving thing is harder. > I'm struggling to unders…

I thought the fundamental hypothesis under discussion here was that the x37 has the orbit to move quickly and avoid interception. It being the second case seems to rule against that hypothesis being true

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

#106

Post by dredmorbius »

euroderf wrote: post #74
dredmorbius wrote: post #35

Earlier quoted context omitted.

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" ?

FYI I'm not familiar with this nor could I find anything. If you could surface a reference I'd be interested in details.

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

#107

Post by euroderf »

dredmorbius wrote: post #106
euroderf wrote: post #74

Earlier quoted context omitted.

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

FYI I'm not familiar with this nor could I find anything. If you could surface a reference I'd be interested in details.

Something I read a long time ago. No reference.

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

#108

Post by jjk166 »

s1artibartfast wrote: post #105
jjk166 wrote: post #104

Earlier quoted context omitted.

> Like the parent says, you already know where it is. The parent is incorrect. You know approximately where it is. If your approximation is off by some amount, you miss. How good of an approximation you have is determined by your detection equipment. How good of an approximation you need is determined by the speed. For the same detection equipment, hitting the faster moving thing is harder. > I'm struggling to unders…

I thought the fundamental hypothesis under discussion here was that the x37 has the orbit to move quickly and avoid interception. It being the second case seems to rule against that hypothesis being true

That is the hypothesis here, and the second case in no way rules against it.

Again to clarify, no one here is arguing that to intercept a target you have to be moving faster than the target. The argument is you have to be moving faster than the minimum speed required to hit a slower target.

In math terms, you have two targets with velocites V1 and V2. To intercept there is some minimum velocity for each, v1 and v2. This is the best case scenario, you are perfectly in position, you can launch at the earliest possible time. v1 < V1 and v2 < V2 are both true. But since V1 < V2, v1 < v2 is also true. An interceptor that can achieve v1 doesn't necessarily have the capability to achieve v2.

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

#109

Post by dredmorbius »

euroderf wrote: post #107
dredmorbius wrote: post #106

Earlier quoted context omitted.

FYI I'm not familiar with this nor could I find anything. If you could surface a reference I'd be interested in details.

Something I read a long time ago. No reference.

No worries, thanks.
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