The Energia had SSTO capability?!?!

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exoscientist

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I was looking up info on the RD-0120 analogue of the shuttle SSME's when I came across this:

Energia EUS.
"Lox/LH2 propellant rocket stage. Loaded/empty mass 77,000/7,000 kg. Thrust 1,962.03 kN. Vacuum specific impulse 455 seconds."
http://www.astronautix.com/stages/eneiaeus.htm

But this is a better than 10 to 1 mass ratio for an LH2/LOX engine. That's sufficient for a SSTO.
Actually the Energia core also appears to have SSTO capability:

Energia Core.
"Lox/LH2 propellant rocket stage. Loaded/empty mass 905,000/85,000 kg. Thrust 7,848.12 kN. Vacuum specific impulse 453 seconds."
http://www.astronautix.com/stages/eneacore.htm



Bob Clark
 
S

scottb50

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exoscientist":2d0verrx said:
I was looking up info on the RD-0120 analogue of the shuttle SSME's when I came across this:

Energia EUS.
"Lox/LH2 propellant rocket stage. Loaded/empty mass 77,000/7,000 kg. Thrust 1,962.03 kN. Vacuum specific impulse 455 seconds."
http://www.astronautix.com/stages/eneiaeus.htm

But this is a better than 10 to 1 mass ratio for an LH2/LOX engine. That's sufficient for a SSTO.
Actually the Energia core also appears to have SSTO capability:

Energia Core.
"Lox/LH2 propellant rocket stage. Loaded/empty mass 905,000/85,000 kg. Thrust 7,848.12 kN. Vacuum specific impulse 453 seconds."
http://www.astronautix.com/stages/eneacore.htm



Bob Clark
The Energia was three stage to orbit, the Core with four Zenit boosters and the payloads, carried like the Shuttle and using their own engines to reach orbit. The satellite version used an upper stage and the Buran used it's OMS engines to reach and define orbit.
 
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exoscientist

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scottb50":3lkaiaia said:
The Energia was three stage to orbit, the Core with four Zenit boosters and the payloads, carried like the Shuttle and using their own engines to reach orbit. The satellite version used an upper stage and the Buran used it's OMS engines to reach and define orbit.
Actually the Energia core stage has the same problem as the shuttle+ET: the hydrogen fueled engines do not have enough thrust alone to lift off the vehicle from the ground. That is why they both use boosters, solids for the shuttle, liquid fueled ones for Energia.
The RD-0120 has a sea level thrust of 154,702 kgf, for a total thrust of 600,000 kgf for the four engines on the Energia core, not enough to lift the 900,000+ kg Energia core stage gross mass:

RD-0120
"Thrust (sl): 1,517.100 kN (341,058 lbf). Thrust (sl): 154,702 kgf. Engine: 3,450 kg (7,600 lb). Chamber Pressure: 218.00 bar. Area Ratio: 85.7. Thrust to Weight Ratio: 57.97. Oxidizer to Fuel Ratio: 6."
http://www.astronautix.com/engines/rd0120.htm

However, the thrust of the single RD-0120 on the Energia EUS upper stage is well above that needed to lift its 77,000 kg gross mass.

Bob Clark
 
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exoscientist

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One advantage of the SSTO is that by orbital refueling it can also be used as a reusable transport to the moon and back. The delta-V requirement for a round-trip mission from LEO to the lunar surface is a little less than that for flights from the Earth's surface to LEO. Then if you could do orbital refueling you could have a single, reusable vehicle that does lunar missions. This fact about SSTO's is well known. It's mentioned for example in G. Harry Stine's very nice book Halfway to Anywhere: Achieving America's Destiny in Space :

"...an SSTO that is refueled in orbit has the capability to fly to the Moon, land, lift off, and fly back without additional refueling."
Halfway to Anywhere: Achieving America's Destiny in Space, p. 220.

This page has a table that gives the delta-V budget in the Earth-Moon system:

Delta-v budget.
Earth–Moon space
http://en.wikipedia.org/wiki/Delta-v_bu ... Moon_space

From this you can calculate that the delta-V for a round trip from LEO to the lunar surface is less than that for getting to LEO from the Earth's surface.

This would be quite useful for cutting the costs of lunar missions.

Bob Clark
 
J

jimoutofthebox

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exoscientist":1jlet1je said:
One advantage of the SSTO is that by orbital refueling it can also be used as a reusable transport to the moon and back. The delta-V requirement for a round-trip mission from LEO to the lunar surface is a little less than that for flights from the Earth's surface to LEO. Then if you could do orbital refueling you could have a single, reusable vehicle that does lunar missions. This fact about SSTO's is well known. It's mentioned for example in G. Harry Stine's very nice book Halfway to Anywhere: Achieving America's Destiny in Space :

"...an SSTO that is refueled in orbit has the capability to fly to the Moon, land, lift off, and fly back without additional refueling."
Halfway to Anywhere: Achieving America's Destiny in Space, p. 220.

This page has a table that gives the delta-V budget in the Earth-Moon system:

Delta-v budget.
Earth–Moon space
http://en.wikipedia.org/wiki/Delta-v_bu ... Moon_space

From this you can calculate that the delta-V for a round trip from LEO to the lunar surface is less than that for getting to LEO from the Earth's surface.

This would be quite useful for cutting the costs of lunar missions.

Bob Clark
Lets say you had a 100 ton SSTO rocket with fuel load of 90 tons and a payload of 3 tons. to refuel it in orbit would require 30 SSTO launches, each with a payload of 3 tons of fuel to refuel the SSTO for a lunar trip. Not real cost effective.
 
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aaron38

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jimoutofthebox":3spjm7sn said:
Lets say you had a 100 ton SSTO rocket with fuel load of 90 tons and a payload of 3 tons. to refuel it in orbit would require 30 SSTO launches, each with a payload of 3 tons of fuel to refuel the SSTO for a lunar trip. Not real cost effective.
Well most likely you wouldn't use the man-rated SSTO for fuel hauling duties. Send a dumb fuel tank up on a big dumb booster, to be met by a tug from the prop depot. But I seriously doubt that any SSTO designed to re-enter and land on Earth would have the mass to spare for the ability to land on an airless moon. It's not just delta-V, but about having the engines pointed in the right direction, and not carrying along useless wings and landing gear.

The lunar transfer vehicle would still be fully reuseable, it would just shuttle between a LEO transfer station and the Moon. The SSTO brings passengers up to the transfer station only.
 
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exoscientist

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aaron38":2zzp59l7 said:
Well most likely you wouldn't use the man-rated SSTO for fuel hauling duties. Send a dumb fuel tank up on a big dumb booster, to be met by a tug from the prop depot. But I seriously doubt that any SSTO designed to re-enter and land on Earth would have the mass to spare for the ability to land on an airless moon. It's not just delta-V, but about having the engines pointed in the right direction, and not carrying along useless wings and landing gear.
The lunar transfer vehicle would still be fully reuseable, it would just shuttle between a LEO transfer station and the Moon. The SSTO brings passengers up to the transfer station only.
Jim does have a point there. This looks like it wouldn't be economical in regards to the fuel being brought up from Earth unless reusable SSTO's do indeed bring the general per kilo launch costs down by 1 to 2 orders of magnitude. But if they do, then you could have for example the large version of the SSTO that had for instance a 30 ton payload capacity make three launches to get to orbit the 90 ton fuel load of the smaller 3 ton payload capacity SSTO.
At a 1 order of magnitude reduction in price to $1,000 per kilo, that 90 ton fuel load would cost $90,000,000. The cost for the smaller SSTO intended for the Moon mission at 3 tons payload would be $3,000,000.
If though the price per kilo to orbit could be reduced by two orders of magnitude with reusable SSTO's as I've argued previously, then the price of the 90 ton fuel load to orbit would only be $9,000,000, and the launch cost of the smaller SSTO launch only $300,000.
But this is for the case that the fuel has to be lugged up from Earth. With reusable SSTO's in general operation both on Earth and on the Moon, then the transport of fuel would be much cheaper because it would instead be brought from the Moon to fuel depots at LEO, which is a much lower delta-V requirement than bringing it from Earth.


Bob Clark
 
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jimoutofthebox

Guest
aaron38":14ebpzfl said:
The lunar transfer vehicle would still be fully reuseable, it would just shuttle between a LEO transfer station and the Moon. The SSTO brings passengers up to the transfer station only.
A throw away lander may still be cheaper. For example- assume a lunar shuttle using aero-braking has an unfueled weight of 30,000 lbs including payload. To lift off from the moon and go to earth the lander would need 40% of its total weight of on the moon as fuel for a total weight of 50,000 lbs on the moon. The same precentage of fuel would be needed to brake and land on the moon so the total weight before braking would be 82,000 lbs. Since the delta V is higher for the TLI burn you would need 50% of the total weight in fuel to go to the moon for a total of 164,000 lbs in LEO. The numbers are rough but I don't think the're too far off. in fact I suspect my estimate for the weight of the lunar shuttle is too low. The fuel tanks alone would probably weigh 30,000 lbs. Also you need to consider that to the best of my knowledge aero-braking to slow a space craft ot orbital speed has never been attempted.
 
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