SpaceX Falcon 9 : X-37B OTV-5 : September 7, 2017 : DISCUSSION

[Prettz]

So do you think the stealth coating is overtop or under the various thermal protection materials?

[macpacheco]

So do you think the stealth coating is overtop or under the various thermal protection materials?

Perhaps on top, and burns up during re-entry and reapplied before each mission.
X-37B has a pretty cozy ride up, only gets cooked on the way down.
Pure speculation of course. But would make sense.

[Kansan52]

Thanks 'z'!

[envy887]

How would "stealth" (radar absorbant materials) help X-37B avoid detection by amateur observers who are looking for it in optical wavelengths?

[rpapo]

If the orbiter were painted or coated with something radar absorbent, then there would have been obvious streaking visible on the orbiter after landing.  We have seen no such thing.

And as noted above, it would not help at all against a flock of amateurs with telescopes.  The only thing that would help with that would be black paint.  But you would get the same streaking effect after reentry with something like that.

Yet the only discoloration we've seen so far was of the same type as the Space Shuttle had after reentry.  For the same reasons.

[Comga]

Three weeks after launch, the searching civilians at Seesat-L have yet to find OTV-5.  I wonder if it might be in a higher inclination orbit than expected.

 - Ed Kyle

Would it be possible for the F9 to have put it in an orbit like ORS-5 where there are no qualified amateur observers actually able to see it.

So is there a sun synchronous orbit that makes satellite viewing difficult?
I would assume if one half is in daylight that would help and if the dark half is over the pacific...

There is, but it has nothing to do with ground features like the Pacific.  (The Pacific ocean is not in constant sunlight or darkness.)

A noon/midnight orbit would be very difficult for ground observers to spot.  The only time it will be illuminated against a dark sky would be at very high latitudes, like above 80 degrees North and South. Not many observers there, or outdoors for long periods at night.

That's not saying that OTV-5 could have been placed there.  It would have been one heck of a plane change to get to the required 97 or so degrees from an East coast launch.  Someone ran the model for me once and said that the Falcon 9 has less than 2 mTons capacity with a plane change that large.  The X-37 is over 5 mTons.  YMMV but it doesn't sound possible.

On the other hand, a very high inclination orbit, but still prograde, might keep it hidden for quite a while. 
OTV-5 launched at 9 AM "local solar time" (10 AM daylight saving time)  It flew "towards noon".  A sharp "left" turn could keep it's visibility pretty far north and south where it could stay for many weeks.

[Prettz]

So do you think the stealth coating is overtop or under the various thermal protection materials?

Perhaps on top, and burns up during re-entry and reapplied before each mission.
X-37B has a pretty cozy ride up, only gets cooked on the way down.
Pure speculation of course. But would make sense.

It was more of a rhetorical question, since both are impossible.

Besides, the X-37 has to keep its payload bay doors open all the while it's in space.

[Star One]

Three weeks after launch, the searching civilians at Seesat-L have yet to find OTV-5.  I wonder if it might be in a higher inclination orbit than expected.

 - Ed Kyle

Would it be possible for the F9 to have put it in an orbit like ORS-5 where there are no qualified amateur observers actually able to see it.

So is there a sun synchronous orbit that makes satellite viewing difficult?
I would assume if one half is in daylight that would help and if the dark half is over the pacific...

There is, but it has nothing to do with ground features like the Pacific.  (The Pacific ocean is not in constant sunlight or darkness.)

A noon/midnight orbit would be very difficult for ground observers to spot.  The only time it will be illuminated against a dark sky would be at very high latitudes, like above 80 degrees North and South. Not many observers there, or outdoors for long periods at night.

That's not saying that OTV-5 could have been placed there.  It would have been one heck of a plane change to get to the required 97 or so degrees from an East coast launch.  Someone ran the model for me once and said that the Falcon 9 has less than 2 mTons capacity with a plane change that large.  The X-37 is over 5 mTons.  YMMV but it doesn't sound possible.

On the other hand, a very high inclination orbit, but still prograde, might keep it hidden for quite a while. 
OTV-5 launched at 9 AM "local solar time" (10 AM daylight saving time)  It flew "towards noon".  A sharp "left" turn could keep it's visibility pretty far north and south where it could stay for many weeks.

Wasn’t there statements beforehand about the F9 having plenty of excess performance with this launch?

[Mader Levap]

Any reliable sources would be under threat of jail time if they said anything.

Using that excuse, you can make up anything about everything claimed to be secret.

I think these Observations just allows other to find it quicker....

Do you seriously think that "others" (presumably Russians and Chinese) rely on USA amateur's observations?

[kevin-rf]

Do you seriously think that "others" (presumably Russians and Chinese) rely on USA amateur's observations?

Actually, it has always surprised me they don't contribute information to the amateur observing community on these secret US payloads. Not so much as a full TLE (that might give away capabilities on how fast they can or can not find and track something) but you know, I would use these search parameters.

Makes one wonder... Of course on a recent NK ballistic missile Russia basically claimed it wasn't an ICBM test by only tracking the first stage... Did they miss the second stage? or was it deliberate subterfuge?

Edit: btw, A good portion of these amateurs are not in the US, or US citizens. It is a very international thing...

[Star One]

Do you seriously think that "others" (presumably Russians and Chinese) rely on USA amateur's observations?

Actually, it has always surprised me they don't contribute information to the amateur observing community on these secret US payloads. Not so much as a full TLE (that might give away capabilities on how fast they can or can not find and track something) but you know, I would use these search parameters.

Makes one wonder... Of course on a recent NK ballistic missile Russia basically claimed it wasn't an ICBM test by only tracking the first stage... Did they miss the second stage? or was it deliberate subterfuge?

Edit: btw, A good portion of these amateurs are not in the US, or US citizens. It is a very international thing...

I doubt they want to tip off their hands to the US as regards their tracking capabilities.

[Kaputnik]

Three weeks after launch, the searching civilians at Seesat-L have yet to find OTV-5.  I wonder if it might be in a higher inclination orbit than expected.

 - Ed Kyle

Would it be possible for the F9 to have put it in an orbit like ORS-5 where there are no qualified amateur observers actually able to see it.

So is there a sun synchronous orbit that makes satellite viewing difficult?
I would assume if one half is in daylight that would help and if the dark half is over the pacific...

There is, but it has nothing to do with ground features like the Pacific.  (The Pacific ocean is not in constant sunlight or darkness.)

A noon/midnight orbit would be very difficult for ground observers to spot.  The only time it will be illuminated against a dark sky would be at very high latitudes, like above 80 degrees North and South. Not many observers there, or outdoors for long periods at night.

That's not saying that OTV-5 could have been placed there.  It would have been one heck of a plane change to get to the required 97 or so degrees from an East coast launch.  Someone ran the model for me once and said that the Falcon 9 has less than 2 mTons capacity with a plane change that large.  The X-37 is over 5 mTons.  YMMV but it doesn't sound possible.

On the other hand, a very high inclination orbit, but still prograde, might keep it hidden for quite a while. 
OTV-5 launched at 9 AM "local solar time" (10 AM daylight saving time)  It flew "towards noon".  A sharp "left" turn could keep it's visibility pretty far north and south where it could stay for many weeks.

Wasn’t there statements beforehand about the F9 having plenty of excess performance with this launch?

Excess performance to a nominal LEO, yes. The OTV is half the mass of a Dragon, for example. But going to a different orbit changes the payload capacity by a huge amount.

[Comga]

Wasn’t there statements beforehand about the F9 having plenty of excess performance with this launch?

Excess performance to a nominal LEO, yes. The OTV is half the mass of a Dragon, for example. But going to a different orbit changes the payload capacity by a huge amount.

I told you.
Someone did a model of the payload capacity of an F9 with a 28 deg plane change. It dropped below 2 tons. East coast launches are limited to ~57 deg so Sun synchronous is almost 40 deg more.
There is a large difference between "more than enough power" and a 40 deg plane change. That's not possible.

[hkultala]

Wasn’t there statements beforehand about the F9 having plenty of excess performance with this launch?

Excess performance to a nominal LEO, yes. The OTV is half the mass of a Dragon, for example. But going to a different orbit changes the payload capacity by a huge amount.

I told you.
Someone did a model of the payload capacity of an F9 with a 28 deg plane change. It dropped below 2 tons. East coast launches are limited to ~57 deg so Sun synchronous is almost 40 deg more.
There is a large difference between "more than enough power" and a 40 deg plane change. That's not possible.

Staging velocity was about 5900 km/h or 1640 m/s at 65km. The 1st stage rose to 136km.

Assuming boostback burn was done horizontally, this means it had 696.5 joules of vertical kinetic energy per kilogram, which means 1.18 km/s vertical velocity during staging.

This means it had 1.14 km/s horizontal velocity during staging.

From the video we see that the boostback burn is not done exactly horizontally but slightly downwards, so it had more than 1.18 km/s vertical velocity during staging, so it had slightly less than 1.14 km/s horizontal velocity during staging. Lets say 1.1 km/s.


40 degrees plane change practically means this initial 1.1 km/s horizontal velocity from the first stage is to 40 degrees wrong direction.  cos(40) = 0.766

So, for this 1.1 velocity the first stage gave it it only  0.766 * 1.1 km/s = 0.84 km/s is "useful work", 0.257 km/s wasted.

This 0.257 km/s is a very small amout of wasted delta-v.


Inclination change is relatively cheap when it's done early enough (immediately after staging of rocket with low-impulse 1st stage). It's very expensive when it's done late.

[Pete]

Staging velocity was about 5900 km/h or 1640 m/s at 65km. The 1st stage rose to 136km.

Assuming boostback burn was done horizontally, this means it had 696.5 joules of vertical kinetic energy per kilogram, which means 1.18 m/s vertical velocity during staging.

This means it had 1.14 m/s horizontal velocity during staging.

Argh!
Ye canna just omit the "k" in "km/s", and assume the audience will fill it in fer ye!

[OneSpeed]

Inclination change is relatively cheap when it's done early enough (immediately after staging of rocket with low-impulse 1st stage). It's very expensive when it's done late.

Taking launch from the Cape to equatorial as an example (28° plane change), the burn needs to be over the equator, which is well after the first S2 shutdown. So, very expensive. I don't know the orbital parameters for OTV-5 yet, but once it is spotted, it may be possible to infer more.

[Lars-J]

Inclination change is relatively cheap when it's done early enough (immediately after staging of rocket with low-impulse 1st stage). It's very expensive when it's done late.

Taking launch from the Cape to equatorial as an example (28° plane change), the burn needs to be over the equator, which is well after the first S2 shutdown. So, very expensive. I don't know the orbital parameters for OTV-5 yet, but once it is spotted, it may be possible to infer more.

LEO inclination changes can be done at any point in the orbit. It is only for GTO elliptical orbits where you really have to do it over the equator, otherwise your apogee is is not going to be over the equator.

[envy887]

Inclination change is relatively cheap when it's done early enough (immediately after staging of rocket with low-impulse 1st stage). It's very expensive when it's done late.

Taking launch from the Cape to equatorial as an example (28° plane change), the burn needs to be over the equator, which is well after the first S2 shutdown. So, very expensive. I don't know the orbital parameters for OTV-5 yet, but once it is spotted, it may be possible to infer more.

LEO inclination changes can be done at any point in the orbit. It is only for GTO elliptical orbits where you really have to do it over the equator, otherwise your apogee is is not going to be over the equator.

Orbital mechanics allow the plane change at any time, but at booster sep the vehicle is only about 100 km downrange and an immediate dogleg to SSO inclinations will trace the upper stage IIP over some highly populated areas.

To get SSO inclinations out of the Cape would require waiting until the upper stage is well out to sea and likely nearly to Newfoundland, more than 1,000 km downrange, where it will be much nearer orbital velocity.

If it was going to SSO, it makes way more sense to launch it from Vandy. It's not like it will be hidden from anyone of importance for long.

[Star One]

Could OTV-5 have been spotted, if it has its much fainter than expected.

http://www.satobs.org/seesat/Sep-2017/0115.html

[hkultala]

Staging velocity was about 5900 km/h or 1640 m/s at 65km. The 1st stage rose to 136km.

Assuming boostback burn was done horizontally, this means it had 696.5 joules of vertical kinetic energy per kilogram, which means 1.18 m/s vertical velocity during staging.

This means it had 1.14 m/s horizontal velocity during staging.

Argh!
Ye canna just omit the "k" in "km/s", and assume the audience will fill it in fer ye!

typoes, and now fixed. But at least I don't use millitesla as unit of mass like most people here.