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Eurockot for Lunar/Interplanetary Missions
by
Danderman
on 22 Nov, 2013 16:49
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This probably was forgotten during the period when Falcon 1 offered a potential very cheap launcher for missions like the Google Lunar X-Prize, but with the loss of Falcon 1, there really isn't an affordable launcher for small interplanetary missions. Except for Eurockot.
Of course, Eurockot cannot by itself launch payloads to the Moon, as the Briz-KM stage has too high a dry mass to be able to inject payloads beyond Earth orbit. The attached chart shows a Star-37 stage as part of the Eurockot payload for an interplanetary mission. The problem with this concept is that a spinning escape stage generates a significant number of constraints on the payload, which Google Lunar X-Prize participants may not be able to meet.
However, I believe that any payload with the delta-V capability of landing on the Moon, or entering Mars orbit, could utilize larger propellant tanks to be able to maneuver from a parking orbit in high Earth orbit to an escape trajectory. For example, Eurockot might be able to inject a 400 kg payload into a 64 degree, 200 km x 20,000 km orbit, from which a spacecraft might be able to use its own engine to escape Earth orbit, using ~ 100 kg of prop. Because the perigee of the orbit does not intersect the Earth's equator, there may be some issues in actually reaching the appropriate trajectory to intersect the Moon's orbit, or Mars, so further analysis is required on this.
The Briz is famous for underburns, but these generally occur either during long burns using the APT drop tank, which is not carried on Eurockot missions, or for stage disposal burns which occur after separation of payload. Neither failure mode is relevant to this case.
If the payload engine ISP is higher than the ISP of the Briz engine, then some offloading of prop from Briz in favor of additional prop loading onto the payload would be useful.
I believe that Eurockot may be a viable small space probe launcher for interplanetary and lunar missions.
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#1
by
Galactic Penguin SST
on 22 Nov, 2013 16:52
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What about Dnepr?
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#2
by
russianhalo117
on 22 Nov, 2013 17:06
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What about Dnepr?
I think i recall that a new upper stage like Breeze-KM would be needed and would replace existing SHM section. otherwise it is not very possible for such missions using existing SHM which cannot be reignited.
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#3
by
plutogno
on 22 Nov, 2013 17:20
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in the early 2000s there was a company, Transorbital, developing a small private lunar orbiter to be launched on Dnepr. I don't remember whether the rocket was supposed to be modified somehow.
They even flew a mockup of their orbiter in one of the first Dnepr launches.
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#4
by
M129K
on 22 Nov, 2013 17:23
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What about Dnepr?
I think i recall that a new upper stage like Breeze-KM would be needed and would replace existing SHM section. otherwise it is not very possible for such missions using existing SHM which cannot be reignited.
Dnepr's higher capacity means that a thrust vectoring Star 48 could be used for high-energy trajectories, rather than a spin-stabilized Star 37.
However, once you consider Dnepr with 4.5 tons to LEO, you enter the range of Antares, so why not that? You also fall onto the doorstep of the empire of the mighty Soyuz. Really, I think that for comparing smaller launchers, we should set some limit on when a launcher is considered small enough. 2.5 tons to LEO?
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#5
by
Danderman
on 22 Nov, 2013 18:33
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Let me suggest that obtaining an export certificate for a Star motor to fly on a Russian ICBM from a Russian launch site may be possible, but difficult.
And in the export field, difficult = expensive.
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#6
by
Danderman
on 22 Nov, 2013 18:34
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What about Dnepr?
Dnepr has a set of system constraints that make it difficult to use in this role.
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#7
by
Star One
on 22 Nov, 2013 19:15
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What about Dnepr?
Dnepr has a set of system constraints that make it difficult to use in this role.
Could you elaborate what these are?
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#8
by
russianhalo117
on 22 Nov, 2013 19:17
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What about Dnepr?
Dnepr has a set of system constraints that make it difficult to use in this role.
Could you elaborate what these are?
part of it is listed in my post further above. the rest i will leave to Danderman
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#9
by
Danderman
on 22 Nov, 2013 22:54
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Dnepr constraints:
The MIRV bus used as the last stage is too robust for use as an escape stage, too much hardware, not enough prop to generate much delta-V.
If instead the Dnepr is to orbit both the payload + some sort of escape stage, there is not much room inside the payload fairing for much of anything.
Kosmostras has always focused on development of a dedicated escape stage specifically designed for Dnepr, since that is probably the optimal solution for that launcher, but there are no customers and so no escape stage. Even with a dedicated escape stage, there isn't much payload for such a large LV.
The lack of customers for Dnepr in this role is an indicator that the Google Lunar X-Prize teams are not close to flying.
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#10
by
Star One
on 23 Nov, 2013 10:17
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Dnepr constraints:
The MIRV bus used as the last stage is too robust for use as an escape stage, too much hardware, not enough prop to generate much delta-V.
If instead the Dnepr is to orbit both the payload + some sort of escape stage, there is not much room inside the payload fairing for much of anything.
Kosmostras has always focused on development of a dedicated escape stage specifically designed for Dnepr, since that is probably the optimal solution for that launcher, but there are no customers and so no escape stage. Even with a dedicated escape stage, there isn't much payload for such a large LV.
The lack of customers for Dnepr in this role is an indicator that the Google Lunar X-Prize teams are not close to flying.
Thanks for this info. From your last comment might you expect Dnepr to have the possibility of launching some of these payloads or would it probably still be off the table even if one or two of the Lunar X-Prize teams showed an interest?
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#11
by
Danderman
on 23 Nov, 2013 14:14
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Dnepr constraints:
The MIRV bus used as the last stage is too robust for use as an escape stage, too much hardware, not enough prop to generate much delta-V.
If instead the Dnepr is to orbit both the payload + some sort of escape stage, there is not much room inside the payload fairing for much of anything.
Kosmostras has always focused on development of a dedicated escape stage specifically designed for Dnepr, since that is probably the optimal solution for that launcher, but there are no customers and so no escape stage. Even with a dedicated escape stage, there isn't much payload for such a large LV.
The lack of customers for Dnepr in this role is an indicator that the Google Lunar X-Prize teams are not close to flying.
Thanks for this info. From your last comment might you expect Dnepr to have the possibility of launching some of these payloads or would it probably still be off the table even if one or two of the Lunar X-Prize teams showed an interest?
IF I were running a Google Lunar X-Prize team, I would consider Dnepr as a launcher because the unit price is fairly low, and I would own a rocket engine that could be used to propel the payload from LEO to the Moon. Since my payload could be designed around the launch vehicle, if necessary, I would be able to configure the prop tanks to fit inside the Dnepr payload fairing.
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#12
by
Danderman
on 23 Nov, 2013 15:20
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Getting back to Eurockot, it would seem that the LV could inject a payload of a few hundred kilograms into a very elliptical orbit that might be some 1500 km/second short of interplanetary. This would require a burn from the payload for Earth escape. Assuming the payload could handle long dwell times in the Van Allen belts, a scheme like the recent ISRO Mars orbiter where many burns by the payload transition the payload from Earth orbit to an interplanetary trajectory could be used, or some sort of electric propulsion like Smart-1 could be used. Or both.
In either case, some apogee burns may be necessary to change the orbital inclination to that required for the appropriate trajectory to the destination. Or, the payload could be injected into a quasi-interplanetary trajectory that returns to Earth, and uses that maneuver to change the inclination. Or use lunar gravity assist.
The point is that Plesetsk, where Eurockot is based, presents challenges for interplanetary trajectories, but these can be overcome with appropriate mission planning.
For some context, the capability of Eurockot in this role (launch to high Earth orbit + use of payload engine for interplanetary injection) is analogous to launching a Mariner 4 class payload. Of course, the 440 pounds weight of Mariner 4 would result in a much more capable spacecraft today.
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#13
by
Danderman
on 26 Nov, 2013 21:55
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With the caveat that Eurockot can only launch from Plesetsk today, it would seem that Eurockot as an interplanetary mission launcher is roughly equivalent to the ISRO PSLV, meaning that mission planners who would accept the risk of a payload based apogee raising maneuver could use Eurockot for interplanetary missions.
I would presume that orbital inclination could be tweaked at apogee with a few small maneuvers, assuming apogee of > 50,000 km.
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#14
by
Danderman
on 29 Nov, 2013 18:06
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If Eurockot is too expensive an option for an interplanetary mission, another approach would be to use Strela. In this case, rather than attain an elliptical orbit with an apogee of > 20,000 km, Strela could only reach about 2,000 km altitude, due to its punier injection stage. This is per the user manual, but this assumes that the injection stage and payload coast after second stage burnout; it might be possible to fire the injection stage immediately after second stage burnout to recover some velocity otherwise lost in the coast (the coast trades velocity for perigee altitude). By eliminating the coast, perhaps a higher apogee could be attained, although the resulting perigee would be very low.
Another approach would be to offload some prop from the injection stage to lower its mass - the Strela second stage is very efficient, whereas the injection stage is very inefficient.