Happy Moon Day!

[KrazyHorse]

Right now, in terms of thrusters the problem is that there's this enormous gap between low-specific impulse, high thrust (chemical) tech and ion thrusters (the inverse).

For interplanetary missions we'd see enormous improvements in flight times if we could trade off in between those two considerations.

[Lorizael]

I already said all that.

[Jon Miller]

There is/was a very valid reason for the government to be involved in early commercial space tech (namely the fact that military apps give you the capability to lift commercial sats). But wtf military application did Apollo have outside of some minor propaganda value (minor compared to the 100 billion dollar price)? What commercial applications have come of it?

I would argue that it served the same thing as having the 1000s of atomic weapons ready to go, which was completely overboard and had less commercial applications.

JM

[KrazyHorse]

Lori

You should know that I only skim your posts.

[KrazyHorse]

I would argue that it served the same thing as having the 1000s of atomic weapons ready to go, which was completely overboard and had less commercial applications.

JM

ICBMs have plenty of commercial application. They're the best investment the US space program has ever made (both in terms of military capability as well as in terms of spinoffs)

[KrazyHorse]

Now, whether or not the US needed 1000s of them is a different story. Actually, I'm not sure if they ever had "thousands" of ICBMs...if my memory serves me correctly the peak was 1000-2000 (launch vehicles, not warheads).

[Jon Miller]

The existence of them is great. My issue is with the number.

Another question, what about 'Star Wars'?

JM

[Az]

It's not. It's (sort of) a political realities issue. The US public would never agree to to use this money for covering debt or something like improvement of education. I think such a solution for actually creating something productive, for engagement in a space race is good propoganda.

????????????

I have no idea what the **** you're talking about. Revenue and expenditure are not directly linked. If the Congress hadn't allocated money to Apollo it does NOT imply that it would have necessarily spent money on something else. It might simply have run less of a deficit/more of a surplus in those years. Or cut taxes, etc.

Congress doesn't HAVE to spend X$ per year, no more no less. They have a soft budget constraint.

It doesn't mean that it has to, of course. But from what I can see from overseas ( might not be a correct vision ) - they usually do. There is some sort of fluid limitation on what amount of money congress is willing to spend each year, and if Space exploration won't take it, some other things will - like defence.

[KrazyHorse]

It doesn't mean that it has to, of course. But from what I can see from overseas ( might not be a correct vision ) - they usually do.

[KrazyHorse]

All of those swings massively dwarf the Apollo project, BTW.

[DanS]

For interplanetary missions we'd see enormous improvements in flight times if we could trade off in between those two considerations.

Chemical propulsion works acceptably for some interplanetary travel -- f.e., Earth to Mars. AFAIK, we could do a ~ 3 month voyage from Earth to Mars using chemical propulsion, given travel at the right time of year. How much would this be reduced with electrical propulsion using something like VASIMR?

Electrical propulsion might be king for longer interplanetary distances in some scenarios (e.g., if no stopover points are contemplated). But it has its expenses too, like handling radioactive materials. If we're in the inner solar system, that trade may not be favorable to electrical propulsion.

[KrazyHorse]

Chemical propulsion works acceptably for some interplanetary travel -- f.e., Earth to Mars. AFAIK, we could do a ~ 3 month voyage from Earth to Mars using chemical propulsion, given travel at the right time of year

a) Earth-Mars is one of the easiest interplanetary trips, and you're still talking 3 months

b) For a 3 month transfer you're talking easily 4X as much fuel as payload (LEO to mars orbit). And since much/most of the cost is in the initial lift from earth your costs go up almost linearly with (fuel+mars arrival) mass. And that's not the worst of it; a lot of what you bring to mars is fuel to get back. So while you aren't quite hit by another factor of 4 (you leave some fuel and equipment at mars) it's quite reasonable to say that payload to fuel is 1:10....in earth orbit. And you lifted all that fuel into earth orbit. And this is what makes it so expensive.

Even minor improvements in the exhaust velocity could drastically reduce those numbers. For example, a 60% increase in exhaust velocity would make the 4:1 number more like 1.5:1 and the overall 10:1 number more like 2:1

[DanS]

I am not really concerned so much about those kinds of fuel to payload ratios. It's true that as we stand today, launch costs Earth-LEO make those ratios difficult. But there are is probably a ~ 1.5 order of magnitude reduction in chemical Earth-LEO launch prices that is low hanging fruit.

Also, we expect that there is a good deal of water on Mars. Likely, we will not have to carry fuel with us on the outbound leg for the return leg.

[KrazyHorse]

But there are is probably a ~ 1.5 order of magnitude reduction in chemical Earth-LEO launch prices that is low hanging fruit.

Dude, there's almost that much with a 60% improvement in exhaust velocity on a relatively slow flight to a nearby planet. If you want to talk about Mars in 4 weeks or the Belt in under a year then the payoff to exhaust velocity is much, much higher (it goes up literally exponentially with delta-v)

[Asher]

Apollo 11's source code has been partially released.

http://googlecode.blogspot.com/2009/07/apollo-11-missions-40th-anniversary-one.html

Excerpt from the Command Module's guidance system:

# Page 883
		BANK	35
		
		SETLOC	BODYATT
		BANK
		
		COUNT	37/CMBAT
		
# PDL 12D - 15D SAFE.

# VALUE OF GIMBAL AND BODY ANGLES VALID AT PIP TIME ARE SAVED DURING  READACCS.

		EBANK=	RTINIT		# LET INTERPRETER SET EB
		
CM/POSE		TC	INTPRET		# COME HERE VIA AVEGEXIT.

		SETPD	VLOAD
			0
			VN		# KVSCALE = (12800/ .3048) /2VS
		VXSC	PDVL
			-KVSCALE	# KVSCALE = .81491944
			UNITW		# FULL UNIT VECTOR
		VXV	VXSC		# VREL = V - WE*R
			UNITR
			KWE
		VAD	STADR
		STORE	-VREL		# SAVE FOR ENTRY GUIDANCE.	REF COORDS
		
		UNIT	LXA,1
			36D		# ABVAL( -VREL) TO X1
		STORE	UXA/2		# -UVREL			REF COORDS
		
		VXV	VCOMP
			UNITR		# .5 UNIT			REF COORDS
		UNIT	SSP		# THE FOLLOWING IS TO PROVIDE A STABLE
			S1		# UN FOR THE END OF THE TERMINAL PHASE.
SPVQUIT		DEC	.019405		# 1000/ 2 VS
		TIX,1	VLOAD		# IF V-VQUIT POS, BRANCH.
			CM/POSE2	# SAME UYA IN OLDUYA
			OLDUYA		# OTHERWISE CONTINUE TO USE OLDUYA
CM/POSE2	STORE	UYA/2		#				REF COORDS

		STORE	OLDUYA		# RESTORE, OR SAVE AS CASE MAY BE.
		
		VXV	VCOMP
			UXA/2		# FINISH OBTAINING TRAJECTORY TRIAD.
		VSL1
		STORE	UZA/2		#				REF COORDS
# Page 884
		TLOAD			# PICK UP CDUX, CDUY, CDUZ CORRESPONDING
			AOG/PIP		# TO PIPUP TIME IN 2'S C AND SAVE.
CM/TRIO		STODL	24D
			25D		# AIG/PIP
			
		RTB	PUSH		# TO PDL0
			CDULOGIC
		COS
		STODL	UBX/2		# CI /2
					# AIG/PIP FROM PDL 0
		SIN	DCOMP
		STODL	UBX/2 +4	# -SI /2
			26D		# AMG/PIP
		RTB	PUSH		# TO PDL 0
			CDULOGIC	
		SIN	PDDL		# XCH PDL 0.  SAVE SM /2
		COS	PDDL		# CM /2 TO PDL 2
			0		# SM /2
		DCOMP	VXSC
			UBX/2
		VSL1			# NOISE WON'T OVFL
		STODL	UBY/2		# =(-SMCI, NOISE, SMSI)/2
			2		# CM /2 REPLACES NOISE
		STODL	UBY/2 +2	# UBY/2=(-SMCI, CM, SMSI)/2
			24D		# AOG/PIP
		RTB	PUSH		# TO PDL 4
			CDULOGIC
		SIN	PDDL		# XCH PDL 4.  SAVE SO /2
		COS	VXSC		# CO /2
			UBY/2
		STODL	UBY/2		# UBY/2=(-COSMCI, COCM, COSMSI)/4
			4D		# SO /2
		DMP	DCOMP
			UBX/2 +4	# -SI /2
		DAD
			UBY/2		# INCREMENT BY (SOSI /4)
		STODL	UBY/2
					# SO /2 FROM PDL 4
		DMP	DAD
			UBX/2		# CI /2
			UBY/2 +4
		STOVL	UBY/2 +4	# YB/4				PLATFORM COORDS
		
					# YB = (-COSMCI + SOSI , COCM , COSMSI + SOCI )
					
			UBY/2
		VXM	VSL2
			REFSMMAT	# .5 UNIT
		STODL	UBY/2		# YB/2 DONE			REF COORDS
# Page 885
					# CM /2 FROM PDL 2
		VXSC	VSL1
			UBX/2
		STODL	UBX/2		# =( CMCI, NOISE, -CMSI)/2
		STADR			# SM /2 FROM PDL 0
		STOVL	UBX/2 +2	# SM /2 REPLACES NOISE
			UBX/2		# XB/2				PLATFORM COORDS
			
					# XB = ( CMCI , SM , -CMSI )
					
		VXM	VSL1
			REFSMMAT	# .5 UNIT
		STORE	UBX/2		# XB/2 DONE			REF COORDS
		
		VXV	VSL1
			UBY/2
		STOVL	UBZ/2		# ZB/2 DONE			REF COORDS
		
					# EQUIVALENT TO
					# ZB = ( SOSMCI + COSI , -SOCM , -SOSMSI + COCI )
					
			UXA/2		# -UVREL/2 = -UVA/2
		VXV	UNIT		# GET UNIT(-UVREL*UBY)/2 = UL/2
			UBY/2		# YB/2
		PUSH	DOT		# UL/2 TO PDL 0,5
			UZA/2		# UNA/2
		STOVL	COSTH		# COS(ROLL)/4
			0		# UL/2
			
		DOT
			UYA/2
		STCALL	SINTH		# -SIN(ROLL)/4
			ARCTRIG
		STOVL	6D		# -(ROLL/180) /2
			UBY/2
		DOT	SL1		# -UVA.UBY = -SIN(BETA)
			UXA/2		# -UVREL/2
		ARCSIN
		STOVL	7D		# -(BETA/180) /2
			UBX/2		# XB/2
		DOT			# UL.UBX = -SIN(ALFA)
			0		# UL/2
		STOVL	SINTH		# -SIN(ALFA)/4
		DOT			# UL/2 FROM PDL 0
			UBZ/2
		STCALL	COSTH		# COS(ALFA)/2
			ARCTRIG
		STOVL	8D		# -(ALFA/180) /2
			UNITR		# UR/2				REF COORDS
		DOT	SL1
# Page 886
			UZA/2		# MORE ACCURATE AT LARGE ARG.
		ARCCOS
		STORE	10D		# (-GAMA/180)/2
		
		TLOAD	EXIT		# ANGLES IN MPAC IN THE ORDER
					# -( (ROLL, BETA, ALFA) /180)/2
			6D		# THESE VALUES CORRECT AT PIPUP TIME.

It's a pretty famous computer, very innovative: http://en.wikipedia.org/wiki/Apollo_Guidance_Computer