SpaceX Dragon spacecraft for low cost trips to the Moon.

[exoscientist]

The Orion spacecraft and Altair lunar lander intended for a manned Moon mission are large craft that would require a heavy lift launcher for the trip. However the Dragon capsule is a smaller capsule that would allow lunar missions with currently existing launchers.
The idea for this use would be for it to act as a reusable shuttle only between LEO and the lunar surface. This page gives the dry mass of the Dragon capsule of 3,180 kg:

SpaceX reveals first Dragon engineering unit.
DATE:16/03/07
By Rob Coppinger
http://www.flightglobal.com/articles/20 ... -unit.html

The wet mass with propellant would be higher than this but for use only as a shuttle between LEO and the Moon, the engines and propellant would be taken up by the attached propulsion system. With crew and supplies call the capsule mass 4,000 kg.
On this listing of space vehicles you can find that the later versions of the Centaur upper stage have a mass ratio of about 10 to 1:

http://www.friends-partners.org/partner ... pndexc.htm

The Isp's given for the RL-10A engines used on these stages are around 450 s, but an updated version with a longer, extensible nozzle has an Isp of 465.5 s:

RL10B-2.
http://www.pratt-whitney.com/StaticFile ... L10B-2.pdf

This page gives the delta-V's needed for trips within the Earth-Moon system:

Delta-V budget.
Earth–Moon space.

http://en.wikipedia.org/wiki/Delta-v_bu ... Moon_space

The architecture will be to use a larger Centaur upper stage to serve as the propulsion system to take the vehicle from LEO to low lunar orbit. This larger stage will not descend to the surface, but will remain in orbit. A smaller Centaur stage will serve as the descent stage and will also serve as the liftoff stage that will take the spacecraft not just back to lunar orbit, but all the way to back to LEO. The larger Centaur stage will return to LEO under its own propulsion, to make the system fully reusable. Both stages will use aerobraking to reduce the delta-V required to return to LEO.
For the larger Centaur, take the gross mass of the stage alone as 30,000 kg, and its dry mass as 1/10th of that at 3,000 kg. For the smaller Centaur stage take the gross mass as 10,000 kg and the dry mass as 1,000 kg. The "Delta-V budget" page gives the delta-V from LEO to low lunar orbit as 4,040 m/s. In calculating the delta-V provided by the larger Centaur stage we'll retain 1,000 kg propellant at the end of the burn for the return trip of this stage to LEO: 465.5*9.8ln((30,000 + 10,000 + 4,000)/(3,000 +10,000 + 4,000 + 1,000)) = 4,077 m/s, sufficient to reach low lunar orbit. For this stage alone to return to LEO, 1,310 m/s delta-V is required. The 1,000 kg retained propellant provides 465.5*9.8ln((3,000 + 1,000)/3,000) = 1,312 m/s, sufficient for the return.
The delta-V to go from low lunar orbit to the Moon's surface is 1,870 m/s. And to go from the Moon's surface back to LEO is 2,740 m/s, for a total of 4,610 m/s. The delta-V provided by this smaller Centaur stage is 465.5*9.8ln((10,000 + 4,000)/(1,000 + 4,000)) = 4,697 m/s, sufficient for lunar landing and the return to LEO.
The RL-10 engine was proven to be reusable for multiple uses with quick turnaround time on the DC-X. The total propellant load of 40,000 kg could be lofted by two 20,000+ kg payload capacity launchers, such as the Atlas V, Delta IV Heavy, Ariane 5, and Proton.
The price for these launchers is in the range of $100-140 million according to the specifications on this page:

Expendable Launch Vehicles.
http://www.spaceandtech.com/spacedata/elvs/elvs.shtml

So two would be in the range of $200-$280 million. The Dragon spacecraft and Centaur stages being reusable for 10+ uses would mean their cost per flight should be significantly less than this. This would bring the cost into the range affordable to be purchased by most national governments.
Still, it would be nice to reduce that $200 million cost just to bring the propellant to orbit. One possibility might be the heavy lift launchers being planned by NASA. One of the main problems in deciding on a design for the launchers is that there would be so few launches the per launch cost would be too high. However, launching of the propellant to orbit for lunar missions would provide a market that could allow multiple launches per year thus reducing the per launch cost of the heavy lift launchers. For instance, the Direct HLV team claims their launcher would cost $240 million per launch if they could make 12 launches per year:

JULY 23, 2009
Interview with Ross Tierney of Direct Launch by Sander Olson.
http://nextbigfuture.com/2009/07/interv ... irect.html

This launcher would have a 70,000 kg payload capacity. However, if you removed the payload fairing and interstage and just kept the propellant to be launched to orbit in the ET itself and considering the fact that the shuttle system was able to launch 100,000+ kg to orbit with the shuttle and payload, it's possible the propellant that could be launched to orbit could be in the range of 100,000 kg. Then the cost per kg to orbit would be $2,400 per kg, or about a $100 million cost for the propellant to orbit.
Reduction of the per launch cost for the heavy lift launchers would then allow affordable launches of the larger spacecraft and landers for lunar missions.


Bob Clark

 

[vattas]

The idea for this use would be for it to act as a reusable shuttle only between LEO and the lunar surface.

I don't see any reason for the capsule, designed for transferring cargo/crew from Earth surface to the orbit and back, to be used as LEO-Moon transfer craft. It's not designed for long duration flight or Moon landing...

 

[exoscientist]

The idea for this use would be for it to act as a reusable shuttle only between LEO and the lunar surface.

I don't see any reason for the capsule, designed for transferring cargo/crew from Earth surface to the orbit and back, to be used as LEO-Moon transfer craft. It's not designed for long duration flight or Moon landing...

It doesn't have to be long duration. Just a few days there and back.

Bob Clark

 

[vattas]

It doesn't have to be long duration. Just a few days there and back.

It doesn't matter. Dragon is designed with other functions in mind. If you need spacecraft to move between LEO and Moon surface, you design vehicle specific for this task. It usually is much more cheaper and effective than trying to adapt something that was designed for completely different purposes.
What is in Dragon that such craft doesn't need:
- Heatshield
- Structure to withstand launch and reentry loads
- Launch/reentry seats.
- Aerodynamic shape
- Landing bags (floatation)
- Parachutes

So if you remove all these things, can we still call it Dragon?
Of course, some things from Dragon can be used to build such craft, such as electronics, Draco thrusters...

 

[exoscientist]

...
The total propellant load of 40,000 kg could be lofted to LEO by two 20,000+ kg payload capacity launchers, such as the Atlas V, Delta IV Heavy, Ariane 5, and Proton.
The price for these launchers is in the range of $100-140 million according to the specifications on this page:

Expendable Launch Vehicles.
http://www.spaceandtech.com/spacedata/elvs/elvs.shtml

So two would be in the range of $200-$280 million. The Dragon spacecraft and Centaur stages being reusable for 10+ uses would mean their cost per flight should be significantly less than this. This would bring the cost into the range affordable to be purchased by most national governments.
Still, it would be nice to reduce that $200 million cost just to bring the propellant to orbit. One possibility might be the heavy lift launchers being planned by NASA. One of the main problems in deciding on a design for the launchers is that there would be so few launches the per launch cost would be too high. However, launching of the propellant to orbit for lunar missions would provide a market that could allow multiple launches per year thus reducing the per launch cost of the heavy lift launchers...

An even lower cost possibility for the capsule and lander might be one proposed by the University of Maryland aerospace engineering department:

Phoenix: A Low-Cost Commercial Approach to the Crew Exploration Vehicle.
http://www.nianet.org/rascal/forum2006/ ... _paper.pdf

As with the Orion CEV, this Phoenix spacecraft was intended to be used in conjunction with a separate lander for lunar missions. However, by using it both for the trip from LEO and as the lander you get great savings in cost.
On page 3 of the report is given a breakdown of the weights of the various subsystems. By removing the propulsion system as I suggested for the Dragon for this purpose, the mass with crew would be about half that of the Dragon, at about 2,000 kg.
Then assuming again 10 to 1 mass ratios for two Centaur style stages for propulsion, we would need about half the propellant load as for the Dragon, about 20,000 kg, which could be lofted by a single launch of the current largest launchers.
Then the cost of lofting this propellant load to LEO would be about $100 million. And if a new heavy lift launcher could get a $2,400 per kg launch price, it would only be in the range of $50 million.
This would increase even further the market for such low cost lunar missions.

Bob Clark

 

[orionrider]

So you are proposing that a stripped-down vehicle that has not been designed for the trip take people to the Moon?
Why bother? The Soviets could have done that ages ago just using the Soyuz. They didn't because it is useless. If you want to observe the Moon, buy binoculars or send a probe.

Unless you intend to land, people are just dead weight. Now, if you mean to land on the Moon, you should think about some landing gear, a reinforced structure, an ascent stage, an airlock, EVA suits, radiation shields, exploration gear, samples containers, etc. This is not a task for a 'Soyuz-like' vehicle like Dragon.

 

[scottb50]

So you are proposing that a stripped-down vehicle that has not been designed for the trip take people to the Moon?
Why bother? The Soviets could have done that ages ago just using the Soyuz. They didn't because it is useless. If you want to observe the Moon, buy binoculars or send a probe.

Unless you intend to land, people are just dead weight. Now, if you mean to land on the Moon, you should think about some landing gear, a reinforced structure, an ascent stage, an airlock, EVA suits, radiation shields, exploration gear, samples containers, etc. This is not a task for a 'Soyuz-like' vehicle like Dragon.

Combine it with a landing module and it would work just fine, like the LEM the Dragon could usue the platform as a launch platform for return to orbit.

 

[orionrider]

Combine it with a landing module and it would work just fine, like the LEM the Dragon could usue the platform as a launch platform for return to orbit.

That's the point, you don't need Dragon, you need a landing module. And a propulsion module. and all the other fancy stuff required for a Moon trip.
Basically, Dragon is a tin can with seats in it, like 40-year-old Soyuz and all the space capsules since Mercury. It's all the rest that is expensive and difficult to build.

 

[TheNavigator]

As a commercial venture (or possible research mission under the NASTAR program) a lunar orbital mission with a manned crew is a feasible option.
Since ROSCOSMOS has conducted the program study regarding the use of a soyuz vehicle for such a mission, it doesn't seem too far outside the realm of possibility to consider the use of a Dragon, or even CST-100 capsule for a lunar orbit mission.
This implies, however the need for a booster engine to exit lunar orbit, additional space for oxygen, CO2 removal scrubbers, food and water storage, retro rockets, and a heat shield capable of withstanding a higher-than-normal speed reentry.

A Space Review article on Soyuz Lunar flights:
http://www.thespacereview.com/article/199/1

An Astronautix article on the soviet sooyuz lunar plans:
http://www.astronautix.com/project/lunarl1.htm

 

[rockett]

SpaceX Dragon lunar mission video. Not likely, since Altair was cancelled, but cool video anyway...

[youtube]http://www.youtube.com/watch?v=jgAaiDAZGA4[/youtube]

 

[SpaceToday]

The argument that some make that these private companies can't make safe vehicles is ridicoulus. Often the people involved in designing and building these vehicles are retired nasa engineers or have worked on successful rocket and spacecraft programs for years. NASA needs to spend money on exploring space not launching toilet paper and food.
http://www.SpaceToday.com

 

[exoscientist]

You still need the capsule to transport the crew from LEO to lunar orbit. I'm proposing combining the capsule and lander into one.
Note that this single lunar orbiter/lander architecture is also being investigated by Lockheed:

Lunar Lander Configurations Incorporating Accessibility, Mobility, and Centaur Cryogenic Propulsion Experience.
Bonnie M. Birckenstaedt1, Josh Hopkins2, Bernard F. Kutter3, Frank Zegler4, Todd Mosher5
Lockheed Martin Space Systems Company, Denver, CO, 80201
"VI. Concept 3: Single Stage Lander
Concept 3 takes advantage of the high Isp of LO2/LH2
propellants to enable a single stage lander to perform
LOI, descent, landing, and ascent to lunar orbit.
Unlike the previous concepts, concept 3 uses a single
RL10-class engine to perform touchdown and ascent
(Fig. 14). This requires deep throttle capability for the
main engine. The CECE engine, with its 10:1 throttle
capability, is baselined for this concept.
In the past, most lunar lander concepts have been
two-stage systems, following the tradition of Apollo.
However, Lockheed Martin has concluded that a
single stage cryogenic lander would probably be less
expensive and not much more massive – in fact a
single stage lander can even be lighter than a two stage
lander. Many engineers would instinctively be
skeptical of a single stage system because on Earth it
has been very difficult to design Single Stage to Orbit
(SSTO) launch vehicles with high enough propellant
mass fraction. However, even if the lander is
responsible for the LOI burn, the lander mission
requires only about half the ΔV of an Earth to orbit
launch, so that both the allowable mass fraction and
the sensitivity to errors in mass fraction are much
lower than for a launch vehicle."

Lunar Lander Configurations Incorporating Accessibility, Mobility, and Centaur Cryogenic Propulsion Experience, p.10
http://unitedlaunchalliance.com/site/do ... 067284.pdf

 

[jimoutofthebox]

I don't think it is safe to use an LH2 engine for the assent stage. While a LH2 engine makes sense for the landing process a hypergolic engine is much safer for the assent due to its rapid response to an abort and its inherent reliability.

 

[rockett]

I don't think it is safe to use an LH2 engine for the assent stage. While a LH2 engine makes sense for the landing process a hypergolic engine is much safer for the assent due to its rapid response to an abort and its inherent reliability.

It would probably be OK based on the amount of experience we have now with LH2 in spacecraft such as the shuttle. However, you do have a point the Apollo LM used Aerozine 50/nitrogen tetroxide (http://en.wikipedia.org/wiki/Aerozine_50) and it was consistantly reliable...

 

[Gravity_Ray]

I think there is a case to be made for tourism to the Moon without landing.

The pluses are that without landing the trip becomes much safer. There is already a case made for rich people that are willing to pay 30-50 million to hop to LEO. For just a bit more you can go on a weeklong trip to orbit the Moon and come back.


You can fly the tourists up to LEO in the Dragon, attach it to a Bigelow style module and push it to the Moon and get there in only a few days. Orbit the Moon for a day or two with some windows on the Bigelow module for sightseeing and then bring the thing back to LEO and land people back with the Dragon leaving the Bigelow style module up there for the next trip.

You can probably get 2-3 trips from the Bigelow module before you de-orbit it and send up another one. If you can get 3-5 tourists to go each time not only will you have a low cost trip, but you will also have a profitable trip.

 

[jimoutofthebox]

I think there is a case to be made for tourism to the Moon without landing.

The pluses are that without landing the trip becomes much safer. There is already a case made for rich people that are willing to pay 30-50 million to hop to LEO. For just a bit more you can go on a weeklong trip to orbit the Moon and come back.


You can fly the tourists up to LEO in the Dragon, attach it to a Bigelow style module and push it to the Moon and get there in only a few days. Orbit the Moon for a day or two with some windows on the Bigelow module for sightseeing and then bring the thing back to LEO and land people back with the Dragon leaving the Bigelow style module up there for the next trip.

You can probably get 2-3 trips from the Bigelow module before you de-orbit it and send up another one. If you can get 3-5 tourists to go each time not only will you have a low cost trip, but you will also have a profitable trip.

The problem is not the size of the spacecraft but the Delta-V required. For example if you built a space craft that could orbit the moon with enough fuel to return it weigh at least 45,000 lbs. To get to the moon you would need a booster with a empty weight of 10,000 lbs plus using LH2 as fuel you would need 55,000 lbs of fuel for a total LEO weight od 55 tons. This doesn't include the fuel and hardware to land on the moon. At this time there is no way to get that much weight in orbit except with several smaller boosters. But linking up mutiple modules would take time and add extra weight all the time your fuel is boiling away.

 

[exoscientist]

I don't think it is safe to use an LH2 engine for the assent stage. While a LH2 engine makes sense for the landing process a hypergolic engine is much safer for the assent due to its rapid response to an abort and its inherent reliability.

It would probably be OK based on the amount of experience we have now with LH2 in spacecraft such as the shuttle. However, you do have a point the Apollo LM used Aerozine 50/nitrogen tetroxide (http://en.wikipedia.org/wiki/Aerozine_50) and it was consistantly reliable...

The Altair lander in the Constellation system was supposed to use hydrogen as well to save on lift off weight.


Bob Clark

 

[jimoutofthebox]

I don't think it is safe to use an LH2 engine for the assent stage. While a LH2 engine makes sense for the landing process a hypergolic engine is much safer for the assent due to its rapid response to an abort and its inherent reliability.

It would probably be OK based on the amount of experience we have now with LH2 in spacecraft such as the shuttle. However, you do have a point the Apollo LM used Aerozine 50/nitrogen tetroxide (http://en.wikipedia.org/wiki/Aerozine_50) and it was consistantly reliable...

The Altair lander in the Constellation system was supposed to use hydrogen as well to save on lift off weight.


Bob Clark

I think the Altair lander design was the thing that most soured me on NASA. I agree that LH2 makes sense for tha landing stage but after two space shuttle disasters it appeared that the designers had learned nothing about robust design. An LH2 engine must have over 100 single points of failure while a hypergolic engine has one. Also if the astronauts are spending weeks on the moon I don't know how they will avoid boiling off all their LH2 in the assent module. In addition the design too heavy with too many bells and whistles. Another thing is the desent stage tank design. If they had of used a design like the Centaur the tanks could have been emptied of fuel, with the fuel converted to water, and the tanks bolted together as the start of a permanent moon base. I could go on, but the point is that NASA never once considered making the Altair design robust and cost effective.

 

[MeteorWayne]

I think the Altair lander design was the thing that most soured me on NASA. I agree that LH2 makes sense for tha landing stage but after two space shuttle disasters it appeared that the designers had learned nothing about robust design.

Which had nothing to do with using LH2 as the fuel...

An LH2 engine must have over 100 single points of failure while a hypergolic engine has one.

Huh?? :lol:

 

[jimoutofthebox]

I think the Altair lander design was the thing that most soured me on NASA. I agree that LH2 makes sense for tha landing stage but after two space shuttle disasters it appeared that the designers had learned nothing about robust design.

Which had nothing to do with using LH2 as the fuel...

I was talking about depending on too much too much complicated interdependent technology with no fail safe back up.

An LH2 engine must have over 100 single points of failure while a hypergolic engine has one.

Huh?? :lol:

A LH2 engine has multiple systems such as turbo pump, igniter, and sequencer. All these system have more subsystems that can fail. An engine like the one used on the lunar lander has a single valve. You open it and the rocket fires. In fact Armstrong wanted to add a manual backup valve to the assent stage so that in a worse case scenerio he could pull a lever to fire the rocket. You can bet that once we loose a crew after their engine quits on the way to orbit every one will ask why we didn't use a proven robust system.

 

[DarkenedOne]

A LH2 engine has multiple systems such as turbo pump, igniter, and sequencer. All these system have more subsystems that can fail. An engine like the one used on the lunar lander has a single valve. You open it and the rocket fires. In fact Armstrong wanted to add a manual backup valve to the assent stage so that in a worse case scenerio he could pull a lever to fire the rocket. You can bet that once we loose a crew after their engine quits on the way to orbit every one will ask why we didn't use a proven robust system.

First of all points of failure is irrelevant. A system's reliability cannot be judged that way. If so your computer which has tens of millions of points of failures given the number of components it has would be the most unreliable thing on Earth. Of course computers run fairly reliably because those tens of millions of components are themselves extremely reliable.

When it comes to the LH2 rocket it is a very reliable and very well proven system. It has been used on every Saturn V launch, every Shuttle launch, and in the launches of a number of commercial vehicles. On the other hand I am not sure, but I do not believe that hyperbolics have the same lengthy record with rockets of that power scale. Therefore I am sure NASA anticipates that they can design a LH2 engine with a very high level of reliability.

Also LH2 rockets are significantly more efficient than the best of the hyperbolics meaning that the LH2 engine requires far less fuel in order to do the same job. This fact is very important because every kg of fuel you add to this part of the mission will require tens of kg in LEO and hundreds if not thousands of kg on the launch pad.

 

[MeteorWayne]

First of all points of failure is irrelevant.

They are never irrelevant.

When it comes to the LH2 rocket it is a very reliable and very well proven system. It has been used on every Saturn V launch,

Well except for the first stage, which was RP-1/LOX

every Shuttle launch,

Well, except for the two SRB's that are required to get it off the ground...

On the other hand I am not sure, but I do not believe that hyperbolics

:lol: :lol:

You can launch anything with hyperbolics... even interstellar spacecraft :lol: :lol: :lol:

 

[pathfinder_01]

A LH2 engine has multiple systems such as turbo pump, igniter, and sequencer. All these system have more subsystems that can fail. An engine like the one used on the lunar lander has a single valve. You open it and the rocket fires. In fact Armstrong wanted to add a manual backup valve to the assent stage so that in a worse case scenerio he could pull a lever to fire the rocket. You can bet that once we loose a crew after their engine quits on the way to orbit every one will ask why we didn't use a proven robust system.

First of all points of failure is irrelevant. A system's reliability cannot be judged that way. If so your computer which has tens of millions of points of failures given the number of components it has would be the most unreliable thing on Earth. Of course computers run fairly reliably because those tens of millions of components are themselves extremely reliable.

When it comes to the LH2 rocket it is a very reliable and very well proven system. It has been used on every Saturn V launch, every Shuttle launch, and in the launches of a number of commercial vehicles. On the other hand I am not sure, but I do not believe that hyperbolics have the same lengthy record with rockets of that power scale. Therefore I am sure NASA anticipates that they can design a LH2 engine with a very high level of reliability.

Also LH2 rockets are significantly more efficient than the best of the hyperbolics meaning that the LH2 engine requires far less fuel in order to do the same job. This fact is very important because every kg of fuel you add to this part of the mission will require tens of kg in LEO and hundreds if not thousands of kg on the launch pad.

It would depend on the purpose of the rocket. Hypergolic is storable. LH2 is not. LH2 has better performance but is more complex. Hypergolic is simpler and less likely to go wrong. LH2 makes sense for an earth departure stage esp. when the crew launches with it. However if the crew needs to spend days in space hypergolic is needed(or some r/d to solve LH2 boil off problem).

 

[jimoutofthebox]

First of all points of failure is irrelevant. A system's reliability cannot be judged that way. If so your computer which has tens of millions of points of failures given the number of components it has would be the most unreliable thing on Earth. Of course computers run fairly reliably because those tens of millions of components are themselves extremely reliable.

When it comes to the LH2 rocket it is a very reliable and very well proven system. It has been used on every Saturn V launch, every Shuttle launch, and in the launches of a number of commercial vehicles. On the other hand I am not sure, but I do not believe that hyperbolics have the same lengthy record with rockets of that power scale. Therefore I am sure NASA anticipates that they can design a LH2 engine with a very high level of reliability.

Also LH2 rockets are significantly more efficient than the best of the hyperbolics meaning that the LH2 engine requires far less fuel in order to do the same job. This fact is very important because every kg of fuel you add to this part of the mission will require tens of kg in LEO and hundreds if not thousands of kg on the launch pad.

To determine total system reliability you mutiply the reliabilty of each critical component. For example if all the components in a 100 componet system each had a failure rate of 1 in 1000 then the failure rate for the system would be .999^100 = .90. Based on these numbers the system will fail 1/10. KISS is best.

Concerning the use of hyperbolics - they were used on the Gemini Titan launcher, Proton booster, the early Ariane boosters, and the Chinese boosters. Pressure fed hyperbolics have been used for thrusters on all US manned missions as well lunar propolusion systems on Apollo. The shuttle uses pressure fed hyperbolics for the OMS engines

 

[Boris_Badenov]

Concerning the use of hyperbolics -

Do mean Hypergolic? Hyperbolic is a mathmatic function.