LRO development Options

[Guest_BruceMoomaw_*]

Let me repeat that the fact that RLEP-2 will be much smaller in size does not mean that its science payload will be cut -- at all. The original design was intended to be the first test of an unmanned cargo lander capable of landing fully 3.5 tons of cargo on the Moon's surface -- and since the total officially planned science payload weighs at most about a ton, they had enormous excess capacity which they were frantically trying to find something to fill.

[Phil Stooke]

PhilHorzempa said: "My suggestion is Surveyor 8." for a new name for RLEP-2.

I can't agree. I think a new design ought to get a new name. Repeating the old name is misleading. But I don't feel there's any urgency.


Phil

[Guest_Analyst_*]

Back to LRO. I never understood the "problem" caused by the Delta II spinning third stage. Many spacecraft with lots of liquid propellant (Near, MGS, MCO, Odyssey, Messenger) launched with this stage with no problem. And the delta V to enter lunar orbit is about the same (1,000 m/s) than entering orbit arround Mars.

I guess the switch to EELV has been because of mass issues and/or political reasons (away from Delta II, more EELV launches).

Analyst

[mcaplinger]

Back to LRO. I never understood the "problem" caused by the Delta II spinning third stage. Many spacecraft with lots of liquid propellant (Near, MGS, MCO, Odyssey, Messenger) launched with this stage with no problem. And the delta V to enter lunar orbit is about the same (1,000 m/s) than entering orbit arround Mars.

The spacecraft you mention all used bipropellant systems. LRO uses a monoprop system with significantly less specific impulse, so it needs more fuel for a given delta-v.

I asked the same question you did, but apparently the tankage involved was outside the experience base of previously-designed antislosh baffles. Probably could have been solved, but it was a development risk.

[Guest_Analyst_*]

Thanks, sounds valid. On the other hand, Messenger does have a lot more delta V than 1,000 m/s, so a monoprop system using Messenger's tanks should give at least 1,000 m/s. They had trouble developing these tanks, but it has been done.

This brings me to another question: Why do never spacecraft (MRO, LRO) use monoprop systems? Biprop systems are working (see my post above) and are well understood and much more efficient. Is the reduced risk and complexity really worth the cost of a bigger launcher (Delta II vs. EELV) and/or less payload?

Analyst

[Jim from NSF.com]

I guess the switch to EELV has been because of mass issues and/or political reasons (away from Delta II, more EELV launches).

Analyst

The Delta II is already "bought". Now another user has to be found. No conspirancy here, NASA would rather keep missions on Delta II because it causes an artificial cost cap for the mission

Thanks, sounds valid. On the other hand, Messenger does have a lot more delta V than 1,000 m/s, so a monoprop system using Messenger's tanks should give at least 1,000 m/s. They had trouble developing these tanks, but it has been done.

This brings me to another question: Why do never spacecraft (MRO, LRO) use monoprop systems? Biprop systems are working (see my post above) and are well understood and much more efficient. Is the reduced risk and complexity really worth the cost of a bigger launcher (Delta II vs. EELV) and/or less payload?

Analyst

The trades actually were in favor of monoprop for MRO. Other than MOI, a biprop, would not be needed. The benefits of simplification of the prop system and elimination of dual hardware was greater than the inefficienies of a monoprop.

[gndonald]

PhilHorzempa said: "My suggestion is Surveyor 8." for a new name for RLEP-2.

I can't agree. I think a new design ought to get a new name. Repeating the old name is misleading. But I don't feel there's any urgency.
Phil

I'll agree there, though perhaps 'Prospector', which was the name of the final planned component of the Ranger/Surveyor/Lunar Orbiter series of probes.

[Guest_DonPMitchell_*]

If there's an impactor mission using the Raytheon proposal, then it may take elements of their previously (allegedly successful) kinetic energy kill vehicle. I've cobbled together a graphic using elements from the Raytheon company site to give an idea of the vehicle - it's got an interesting take on attitude control/translation with rocket nozzles set, I presume, around the vehicle's CG.

Bob Shaw

Very cool. Something sci-fi writers rarely seem to get, that kinetic-energy really is a very good way to dump energy into something. When people are busy shooting at each other in space someday, they will likely be firing bullets, not ray guns.

[ljk4-1]

Very cool. Something sci-fi writers rarely seem to get, that kinetic-energy really is a very good way to dump energy into something. When people are busy shooting at each other in space someday, they will likely be firing bullets, not ray guns.

Oh please, Don - human beings would NEVER take their aggressions and
other primate behaviors into space.

Is there a sarcasm/irony face available?

FYI - It has already happened at least once. Salyut 3 had a self-defense
gun which it test fired. You can see it here:

http://www.russianspaceweb.com/almaz_ops2.html

[Guest_DonPMitchell_*]

Oh please, Don - human beings would NEVER take their aggressions and
other primate behaviors into space.

Is there a sarcasm/irony face available?

FYI - It has already happened at least once. Salyut 3 had a self-defense
gun which it test fired. You can see it here:

http://www.russianspaceweb.com/almaz_ops2.html

I believe both Russia and the United States have developed anti-satellite satellites. Sven Grahn has a nice page about the Soviet Polyot experiments here: ASAT

When I was at Caltech around 1980, Seasat malfunctioned shortly after launch. There were many interesting rumors circulating about this satellite, from graudate students associated with JPL. One was that the military was able to Fourier-analyze the Seasat data to detect the wakes of nuclear submarines. The other was that the Soviet Union knew that and destroyed the satellite with ground-based laser while it passed over their territory. Just rumors of course...

[Guest_BruceMoomaw_*]

That first rumor about Seasat's early demise got around a lot -- I remember seeing it somewhere in the science literature at the time.

It's certainly more plausible than the second rumor; if the Russkies had shot up Seasat, then the US could just have sent up a replacement -- and if the Russkies had shot that one down too, we would have been in Cuban Missile Crisis territory again in jig time.

[Guest_DonPMitchell_*]

That first rumor about Seasat's early demise got around a lot -- I remember seeing it somewhere in the science literature at the time.

It's certainly more plausible than the second rumor; if the Russkies had shot up Seasat, then the US could just have sent up a replcement -- and if the Russkies had shot that one down too, we would have been in Cuban Missile Crisis territory again in jig time.

I agree. I think they could have done it, they pretty much wrote the book on lasers and phase-conjugate optics, but I don't believe they would have done something that overt.

I would not be surprised if there was some negociation about the technology. One side being able to see submarines could be interpreted as strategically unstable. Nuclear submarines are a major deterant to first strike.

Oh wow, my 100th post. I'm not a Junior anymore. :-)

[mchan]

I recall reading some Congressional hearings transcripts on this. Basically, the testimony was that subs could not be detected by the Seasat SAR. Some ocean images were shown of where there were supposedly US subs. Of course, there was nothing that stood out visually. But nothing was said on signal processing the data to look at it in different ways, e.g., frequency domain analysis as mentioned above.

That said, however, the technology goes both ways. The US would have had more to lose than the Soviets from a space-based sensor capability that would render the oceans transparent. Unless, of course, there is a lag to one side acquiring the technology and the other side actually uses its technological advantage while it has it. Which happily never took place.

[ljk4-1]

Who needs fancy and expensive laser weapons to wipe out
space satellites? Just send up a bucket of rocks and pebbles
and let them loose at 18,000 MPH.

[ljk4-1]

I'll agree there, though perhaps 'Prospector', which was the name of the final planned component of the Ranger/Surveyor/Lunar Orbiter series of probes.

Here is a drawing of the original Prospector robotic lunar rover:

http://utenti.lycos.it/paoloulivi/prospect.jpg