Real Solar System Challenge: Falcon Heavy mission to Europa.

[Exoscientist]

 It was recently announced that the Falcon Heavy has been selected to carry the Europa Clipper orbiter mission to Europa. The debate between the much more expensive SLS over the FH was that the SLS could do it in less than 3 years, while the FH would need 6 years, requiring gravitational slingshots.

 However in point of fact by using high efficiency in-space stages such as the Centaur, the FH can also do it in 3 years, no gravitational slingshots required. Moreover, it can even do lander missions, not just orbital.  See calculations here:

Low cost Europa lander missions. 

http://exoscientist.blogspot.com/2015/02/low-cost-europa-lander-missions.html 

 Who’s up to this challenge?

   Robert Clark

[swjr-swis]

 

[Exoscientist]

On 7/27/2021 at 12:43 PM, swjr-swis said:

 

 

 Let me modify it: any Real Solar System simulation of a Falcon Heavy launched flight to Europa would be very interesting to see, including just the orbital one planned and including ones using gravitational assists.

 By the way, another one of the suggestions for making a good challenge is doing one yourself first.

 At this point, I do need to start learning kerbal instead of just reading about it.

    Robert Clark

[Exoscientist]

 

 I found Kerbal RSS mission to  Europa on Youtube, that gives a mass of the spacecraft including propellant as 9 tons launched by the Delta IV Heavy:

 

 Problem is I’m fairly sure the Delta IV Heavy could not launch that much mass to Jupiter with no gravity assists as shown in the video. It might be able to launch a much smaller mass, say, 2 tons.

  Robert Clark 

[jinnantonix]

The video above is not realistic, whether using a Delta Heavy, a Falcon Heavy, or SLS.  

Firstly the Europa Clipper mission does not go to Europa orbit, but instead the probe remains in Jupiter elliptical and does 44 Europa fly-bys.    The reason for this is to avoid Jupiter's radiation, and also giving the craft plenty of time to send its data back to Earth.  Even avoiding the worst of the radiation, the mission includes 150kg of radiation shielding enclosing 82kg of instruments. It would make very little sense to forego all that science just to land on Europa.

I think a Europa Lander would piggy back off the Clipper main orbiter probe.  The Clipper/Lander assembly use an IABS to insert into Jupiter elliptical orbit.  Then the Europa Lander decouples to land on Europa (dV ~5000 m/s) using the IABS for propulsion.  The Lander payload would need to be tiny, carrying minimal science instrumentation, and would only last a few weeks before all electronics would be fried.  A cubesat (1.5kg), with a seismometer and mass spectrometer (@ 5kg) for measuring surface samples, short range comms relayed via the orbiter.  The lander craft would be reliant on batteries only to conduct a few experiments, transmit the data, and then expire.  For propulsion, the lander would need to use the main IABS propulsion unit, leaving behind a small attitude propulsion unit with the main orbiter probe, utilising 4 x thruster blocks.

Europa Clipper probe comprises shielding, probe core, 9 x science instruments, batteries/solar panels,  comms dish, 4x RV-1X thruster blocks

The Europa lander, comprising cubesat, two science instruments and batteries, and IABS - hex core, short-range comms, two spiders (R-4D) and RV-1X thruster block.

The Europa Clipper has a mass= 6065 kg wet including all fuel for the journey, and the Lander instruments and additional propulsion would need to be added to that.

 

 

Edited August 12, 2021 by jinnantonix

[jinnantonix]

Regarding the use of two Centaurs, would these be stacked one on top of the other, in a two stage arrangement?  That would make the TJI stage over 26m high, or double the standard FH fairing height.  The shorter, wider DCSS would be more suitable, very similar specs to the Centaur.  Total height for two stage DCSS based payload =~17m (+ 5m for the Europa Clipper probe + ~2 m for the Europa Lander probe).  Could the SpaceX engineers make this modification?  IMHO, a single Centaur / DCSS would be the limit of available space.

The Centaur and the DCSS have a wet mass of 20t, plus the probes (Clipper and Lander) and their fuel . The FHe has a payload capability to LEO of 64t.  So there would be plenty of fuel in the final stage of the FH to give the craft a good push toward Jupiter, and shave off some of the 6km/s delta V required.

Edited August 3, 2021 by jinnantonix

[jinnantonix]

Here is my model for the Falcon Heavy in Real Solar System.  It matches real world quite well, can carry a 64 ton payload to LEO (just).

 

 

[jinnantonix]

The Europa Clipper probe has a launch mass of 6065 kg, including "all the fuel for the mission", which at a minimum would be enough for Jupiter insertion to an elliptical orbit with a period of 2-4 weeks, plus extra for manoeuvres, I would estimate a minimum of about dV = 1000 m/s  is needed for the transit mid-flight adjusts.

According to my simulation of the FHe with Clipper probe, the second stage rEeaches LEO with enough remaining fuel to provide a delta-V of 6.445 km/s , which is more than enough to transit direct from Earth to Jupiter.  So why do NASA require the Mars -Earth gravity assist?  I can only assume that NASA only wants to pay for a lower cost  launch with booster recovery.  NASA paid SpaceX $176 million for the contract, but there may be development costs bundled into that.  Alternatively, and perhaps more likely, NASA has simply built in a design safety factor, to reserve as much fuel as possible for when the probe is in Jovian orbit.

Edit:   But this excludes the Star 48 which has a wet mass of 2t.  Hence the FHe does not have enough dV for TJI, but does have enough for trans-Mars injection.

Can a lander probe be added to the payload and reach Jupiter orbit.  Here's what needs to be done to verify:

• A lander must be devised to deliver some science experiments from the Europa Clipper probe orbit to the surface of Europa.  (dV = 2700 m.s?).  What would be the launch mass?
• With this additional mass, what is the dV of the FHe second stage at LEO, and is this sufficient to transit to Jupiter?  (with gravity assist?)
• If not, would adding a third stage (e.g. a Centaur or DCSS) improve the efficiency sufficiently, noting Merlin Vac Isp = 311 and RL-10 Isp = 465.

Edited August 12, 2021 by jinnantonix

[jinnantonix]

Europa Lander

Mass (wet) = 1019kg.  Includes 30kg science experiments, 15kg batteries.  Propulsion is based on IABS with 2 x R4-D engines, but uses ACS: 12 x MR-111 thrusters

Edit:  this is far too heavy to be accepted and remain within NASA's conservative limit of 273kg for the piggyback.  Back to the drawing board and spreadsheet.  Looking to the prelim design studies Sylph "SmallSat", Mini-Maggie (CubeSat) and ELSA Neopod.

Edited August 7, 2021 by jinnantonix

[camacju]

3 hours ago, jinnantonix said:

and is this sufficient to transit to Jupiter?

All you need is enough for a Moon transfer and you're good to go anywhere probably

(Wow I typed Mun by instinct at first )

[jinnantonix]

With  the lander, the launch mass = 7085 kg.  According to my simulation of the FHe with Clipper probe, the second stage reaches LEO with enough remaining fuel to provide a delta-V of 6.225 km/s, which is nearly enough to transit direct from Earth to Jupiter.  I would assume that surely the extra 75 m/s could be provided by the Europa Clipper engines during a mid transit adjust.

8 minutes ago, camacju said:

All you need is enough for a Moon transfer and you're good to go anywhere probably

(Wow I typed Mun by instinct at first )

If that were so, why do so few deep space launches use the Moon for gravity assist?  I don't think the Mun provides a good replication of real world gravity assists.

[camacju]

4 hours ago, jinnantonix said:

If that were so, why do so few deep space launches use the Moon for gravity assist?  I don't think the Mun provides a good replication of real world gravity assists

I feel like it's due to deltav-time tradeoffs. Cosmic rays scrambling computer memory, etc

[jinnantonix]

15 hours ago, camacju said:

I feel like it's due to deltav-time tradeoffs. Cosmic rays scrambling computer memory, etc

It's mainly due to timing of Hohmann transfers. IRL there is a typically a preference for one big Oberth burn using a hydrogen fuelled second or third stage. The Moon has an orbital period of about one month, whereas the launch window for an interplanetary mission is a few days at most.  The Moon is rarely in the correct position to provide a significant gravity assist for the outbound craft.  It can be done however, where the the final launch stage burns to TLI, and the upper stage then uses hypergolic fuel and multiple Moon gravity assists to raise Ap before a final Oberth burn at the Moon to reach solar orbit.

 

Edited August 7, 2021 by jinnantonix

[jinnantonix]

I have had a lot of fun building and testing Europa Landers, and can now categorically say the it is impossible to land a science experiment within the NASA's piggyback constraint of the 273kg mass limit.   The craft needs 3500 m/s to transit from elliptical Jovian orbit to Europa orbit, and another 1500 m/s to land.   For 20kg of science instruments, the best vehicle mass I could do was 750kg .   

I was however successful in building a model that could get into Europa polar orbit.  

• Science instrument:  Multi Spectral Imaging, including mass spectrometer 20kg
• Batteries:  Lipo, 5kg
• Medium gain antenna 2kg
• Craft body and thrusters 15kg
• R-4D engine 20kg
• Propellant 150kg .  dV =3532 m/s, unshielded
• Radiation shielding for transit 60kg

The craft remains shielded until it reaches Europa, decoupling before orbital burn.  The craft then orbits in low Europa orbit every 2 hours transmitting science data to the Clipper probe for as long as the battery lasts.

 

 

[Exoscientist]

On 8/2/2021 at 8:34 AM, jinnantonix said:

The video above is not realistic, whether using a Delta Heavy, a Falcon Heavy, or SLS.  

Firstly the Europa Clipper mission does not go to Europa orbit, but instead the probe remains in Jupiter elliptical and does 44 Europa fly-bys.    The reason for this is to avoid Jupiter's radiation, and also giving the craft plenty of time to send its data back to Earth.  Even avoiding the worst of the radiation, the mission includes 150kg of radiation shielding enclosing 82kg of instruments. It would make very little sense to forego all that science just to land on Europa.

...

 Thanks for that. I wrote to the author of the Youtube video showing a RSS Europa landing simulation. He said it was not a Delta IV Heavy launcher despite its triple-cored  appearance. It was actually a much heavier vehicle of his own design.

 

  Robert Clark

On 8/2/2021 at 9:57 AM, jinnantonix said:

Regarding the use of two Centaurs, would these be stacked one on top of the other, in a two stage arrangement?  That would make the TJI stage over 26m high, or double the standard FH fairing height.  The shorter, wider DCSS would be more suitable, very similar specs to the Centaur.  Total height for two stage DCSS based payload =~17m (+ 5m for the Europa Clipper probe + ~2 m for the Europa Lander probe).  Could the SpaceX engineers make this modification?  IMHO, a single Centaur / DCSS would be the limit of available space.

The Centaur and the DCSS have a wet mass of 20t, plus the probes (Clipper and Lander) and their fuel . The FHe has a payload capability to LEO of 64t.  So there would be plenty of fuel in the final stage of the FH to give the craft a good push toward Jupiter, and shave off some of the 6km/s delta V required.

 Actually the upper stage of the Delta IV Heavy would be even better at a propellant load of 27 tons, gross mass 30 tons. It’s described on the wiki page on the DCSS you linked to.

 Even better yet would be the Centaur V upper stage planned for ULA’s Vulcan Centaur. It’s to have a propellant load twice as large at 54 tons.

 

  Robert Clark

Edited August 9, 2021 by Exoscientist

[Exoscientist]

On 8/6/2021 at 6:01 AM, jinnantonix said:

The Europa Clipper probe has a launch mass of 6065 kg, including "all the fuel for the mission", which at a minimum would be enough for Jupiter insertion to an elliptical orbit with a period of 2-4 weeks, plus extra for manoeuvres, I would estimate a minimum of about dV = 1000 m/s, plus whatever is needed for the transit mid-flight adjusts.

According to my simulation of the FHe with Clipper probe, the second stage reaches LEO with enough remaining fuel to provide a delta-V of 6.445 km/s, which is more than enough to transit direct from Earth to Jupiter.  So why do NASA require the Mars -Earth gravity assist?  I can only assume that NASA only wants to pay for a lower cost  launch with booster recovery.  NASA paid SpaceX $176 million for the contract, but there may be development costs bundled into that.  Alternatively, and perhaps more likely, NASA has simply built in a design safety factor, to reserve as much fuel as possible for when the probe is in Jovian orbit.

Can a lander probe be added to the payload and reach Jupiter orbit.  Here's what needs to be done to verify:

• A lander must be devised to deliver some science experiments from the Europa Clipper probe orbit to the surface of Europa.  (dV = 2700 m.s?).  What would be the launch mass?
• With this additional mass, what is the dV of the FHe second stage at LEO, and is this sufficient to transit to Jupiter?  (with gravity assist?)
• If not, would adding a third stage (e.g. a Centaur or DCSS) improve the efficiency sufficiently, noting Merlin Vac Isp = 311 and RL-10 Isp = 465.

 

 Thanks for that. This page estimates payloads possible of various launchers: http://www.silverbirdastronautics.com/cgi-bin/LVPcalc.pl

The C3, i.e., hyperbolic excess velocity, of the flight to Jupiter is ~80 km²/s². The calculator estimates the payload of the FH there as 5,000 kg with a possible maximum up to 6,400 kg.

 It might be NASA wanted more margin to be assured of success. 

  Robert Clark

On 8/6/2021 at 9:09 AM, camacju said:

All you need is enough for a Moon transfer and you're good to go anywhere probably

(Wow I typed Mun by instinct at first )

 Moon transfer? You mean landing on the Moon for a refueling?

   Robert Clark

[Exoscientist]

On 8/8/2021 at 4:29 AM, jinnantonix said:

I have had a lot of fun building and testing Europa Landers, and can now categorically say the it is impossible to land a science experiment within the NASA's piggyback constraint of the 273kg mass limit.   The craft needs 3500 m/s to transit from elliptical Jovian orbit to Europa orbit, and another 1500 m/s to land.   For 20kg of science instruments, the best vehicle mass I could do was 750kg .   

I was however successful in building a model that could get into Europa polar orbit.  

• Science instrument:  Multi Spectral Imaging, including mass spectrometer 20kg
• Batteries:  Lipo, 5kg
• Medium gain antenna 2kg
• Craft body and thrusters 15kg
• R-4D engine 20kg
• Propellant 150kg .  dV =3532 m/s, unshielded
• Radiation shielding for transit 60kg

The craft remains shielded until it reaches Europa, decoupling before orbital burn.  The craft then orbits in low Europa orbit every 2 hours transmitting science data to the Clipper probe for as long as the battery lasts.

 

 

 

 What could you do with the addition to the FH of a hydrolox stage such as the 5-meter upper stage of the Delta IV Heavy at 27 ton propellant load or the Centaur V upper stage of the Vulcan Centaur at 54 ton propellant load?

 Actually the lander mission is so important, arguably more important than a Jovian-system orbiting mission, that at a ca. $150 million FH launch price it would be worth it for a lander mission to have its own dedicated FH launch.

 

  Robert Clark

 

Edited August 9, 2021 by Exoscientist

[jinnantonix]

5 hours ago, Exoscientist said:

Actually the lander mission is so important, arguably more important than a Jovian-system orbiting mission, that at a ca. $150 million FH launch price it would be worth it for a lander mission to have its own dedicated FH launch.

Is a lander mission more important than the Jovian-system orbiting mission?  

Firstly, it would not be possible to land on Europa without a very detailed survey of the surface topography.  This could not be gathered efficiently from Europa orbit, because any mission that persists close to Jupiter will be subjected to harsh radiation that will limit the time available for collection and transmission of data.  The Clipper mission's fly-by design has the advantage that it minimises radiation exposure to the craft, and also uses the time in higher altitude orbit to transmit the collected data back to Earth.  Europa Clipper will be gathering all the required initial surface topography data from many fly-by passes and detailed analysis.

It should be noted that any lander mission will be constrained by the payload of science instrumentation, and also the fact that it will only be able to survive the harsh radiation environment for a few weeks at most, as shielding will be too heavy to land with the surface probe.    It is arguable that carrying a RTG or solar power system to the surface is therefore not justified, and the mission would likely be constrained by battery power capacity.  Instruments should definitely be both a standard mass and Raman laser mass spectrometer, and a seismometer, noting that seismic data would be of questionable  value with such limited time on the surface, and also has the problem that it generates large amounts of data for upload.

Considering this, and the fact that a Jovian orbiter can carry much more science payload, and can generate a lot more science, plus has the time and opportunity to transmit that data back to Earth, I would argue that the Europa Clipper orbiter is certainly the best design for the initial mission.

NASA has acknowledged that the lander mission is important and so is investigating an entirely separate mission with the target to put a lander on the surface of Europa, possibly with a separate craft in low Europa orbit with relay capability.  The mission cost would be in the vicinity of $3.5 billion.  That is a lot of money for a probe that will probably only remain active for 3-4 weeks on the surface, and gather only some surface chemistry  (which could otherwise be obtained from plume data) and limited seismic data.  We all are inspired by the idea of a lander, but is it worth it?

Considering this, the costly and risky notion of beefing up the Europa Clipper mission with a Centaur or DCSS  third stage is moot.  It is clear, NASA wants to avoid risk to focus on the success of the more valuable Clipper mission, and is quite willing to wait for the Mars-Earth gravity assist in order to reduce risk and ensure success.  Further speculation is not a valuable exercise.

Having said that, it seems a waste leaving the possibility of adding a 273kg payload to collect more science .  Having looked at the many proposals for using the piggyback option, I favour a Europa orbiter with an impact test to determine surface chemistry and also to collect more accurate data on Europa's tenuous atmosphere (plumes).
 

Quote

Actually the upper stage of the Delta IV Heavy would be even better at a propellant load of 27 tons, gross mass 30 tons. It’s described on the wiki page on the DCSS you linked to.

 Even better yet would be the Centaur V upper stage planned for ULA’s Vulcan Centaur. It’s to have a propellant load twice as large at 54 tons.

The Delta IV Heavy has been retired, at $400 M per launch it cannot compete with SpaceX Falcon Heavy nor the impending Blue Origin New Glenn.

The ULA Vulcan with a Centaur V upper stage will no doubt be a future contender for NASA contracts, but is still not projected to beat a FHe for maximum payload.
 

Edited August 9, 2021 by jinnantonix

[jinnantonix]

Europa Clipper with piggyback Orbiter (and now Star 48 "kicker") fitting perfectly into the Falcon payload fairing. 

Edited August 11, 2021 by jinnantonix

[jinnantonix]

On 8/10/2021 at 3:38 AM, Exoscientist said:

 

 The calculator estimates the payload of the FH there as 5,000 kg with a possible maximum up to 6,400 kg.

 It might be NASA wanted more margin to be assured of success. 

 

While researching I stumbled on this - the launch will include a Star 48 "kicker"

Star 48B SPEC:  AKA: 87.2-KS-17,735;TE-M-799. Status: In Production. Thrust: 66.00 kN (14,837 lbf). Gross mass: 2,137 kg (4,711 lb). Unfuelled mass: 126 kg (277 lb). Specific impulse: 286 s. Burn time: 87 s. Height: 2.03 m (6.67 ft). Diameter: 1.25 m (4.08 ft).

This makes the launch payload as follows:

Europa Clipper: 6065kg
Piggyback payload:  273kg
Star 48B: 2,137 kg

Total = 8,475 kg

The FHe cannot get this to Jupiter, but it definitely can get it to Mars.  So that is clearly why this mission requires the Mars  - Earth gravity assist to reach Jupiter.

Star 48

Modelled with a Terrier engine and a "tweakscaled" R-4 Dumpling fuel tank

Edited August 12, 2021 by jinnantonix

[jinnantonix]

A question for those good at calculating orbital mechanics.

NASA advise that the following is the schedule for the Europa Clipper transit to Jupiter:

• launch in October 2024 -  21-day launch window.
• Mars in February 2025
• Earth in December 2026,
• arriving at Europa in April 2030.
   

So 128 days from LEO to Mars?  And then 1 year and 9 months back to Earth?  

Edited August 12, 2021 by jinnantonix

[jinnantonix]

This is the trajectory planned.  I am still not sure how the Star 48 is used  Apparently not for a DSM.   It is either at the start during TMI , or it is used to decelerate at Jupiter.  The latter seems unlikley because I am not sure if the engine would be reliable after 4 years in deep space.

 

[Exoscientist]

On 8/10/2021 at 8:32 PM, jinnantonix said:

While researching I stumbled on this - the launch will include a Star 48 "kicker"

Star 48B SPEC:  AKA: 87.2-KS-17,735;TE-M-799. Status: In Production. Thrust: 66.00 kN (14,837 lbf). Gross mass: 2,137 kg (4,711 lb). Unfuelled mass: 126 kg (277 lb). Specific impulse: 286 s. Burn time: 87 s. Height: 2.03 m (6.67 ft). Diameter: 1.25 m (4.08 ft).

This makes the launch payload as follows:

Europa Clipper: 6065kg
Piggyback payload:  273kg
Star 48B: 2,137 kg

Total = 8,475 kg

The FHe cannot get this to Jupiter, but it definitely can get it to Mars.  So that is clearly why this mission requires the Mars  - Earth gravity assist to reach Jupiter.
...

 Thanks for that. I hadn’t known that.

 BTW, the reason why I think a lander mission could be more important than an orbiter mission is because I was assuming such a mission would tunnel though the ice to the subsurface ocean. This raises the possibility it could discover advanced life-forms, an Earth-shattering discovery. 

 A lander mission that just stayed on the surface could find at most microbial life, and even that is doubtful considering the high radiation environment.

 The key question though: how to tunnel through kilometers of ice in a manner not requiring too much power or mass?

  Robert Clark

Edited August 13, 2021 by Exoscientist

[jinnantonix]

1 hour ago, Exoscientist said:

 Thanks for that. I hadn’t known that.

 BTW, the reason why I think a lander mission could be more important than an orbiter mission is because I was assuming such a mission would tunnel though the ice to the subsurface ocean. This raises the possibility it could discover advanced life-forms, an Earth-shattering discovery. 

 A lander mission that just stayed on the surface could find at most microbial life, and even that is doubtful considering the high radiation environment.

 The key question though: how to tunnel though kilometers of ice in a manner not requiring too much power or mass?

  Robert Clark

Sending a submarine to Europa is an inspiring notion, but is presently science fiction, mainly because of the difficulty of drilling through 30km of ice crust.  Humans have not been able to do that on Earth (yet).  The concept of Cryobot may offer an answer, a lot of development needed.  How much energy would be required to melt ice at an ambient temperature of -160 degC?   Then the sub would need to survive 10,000 atmospheres of pressure.  And finally how would the sub communicate and return data to Earth?

Landing on Europa, while an inspiring thought, is logistically complex.  Finding a safe landing site requires very detailed data.  There is no atmosphere for braking velocity, or to provide passive stability.  A skycrane would be needed so that the engine exhaust does not contaminate the surface and ruin the ability to collect pristine samples.  Advanced AI would be required to pilot the craft completely autonomously.  etc, etc.  Technically it can be done, but it will not be cheap, nor without high risk of catastrophic failure.  One false move, and $3.5 billion is entirely wasted.

The detailed measurement of the plumes around Europa will reveal the chemistry of the subsurface ocean.  The Europa Clipper will be making such measurements during each fly-by.  The potential for life could deduced from such data.  Perhaps a sampling mass spectrometer may even be able to identify dead alien microbes in the plumes?  This would not require a lander, but a craft in orbit around Europa could make more accurate measurements.  A lander mission  (assuming no submarine) would really only accurately measure the chemistry of the surface, there isn't much else to be learned.  But this could be more cheaply determined by an impacter with plume measurement by an orbiter.  I have modelled such an experiment as a piggyback mission on the Europa Clipper, occupying the 273kg mass offered by NASA for additional science missions.
 

Edited August 13, 2021 by jinnantonix

[jinnantonix]

With regard to the Star 48 kickstage.

Lou Scheffer blogs https://forum.nasaspaceflight.com/index.php?topic=47579.msg2276806#msg2276806:

Quote

The Europa Clipper spacecraft masses just about 6000 kg.  The launch selection document says the rocket needs to launch a payload of 6065 kg to a C3 of 42.  A Star-48 masses 2100 kg, so it can't possibly be included.

The NASA LSP web site says the FH can launch 6400 kg to a C3 of 42, without a kick stage.   Therefore there is no need for one, so it's not included.

The photo shows the adapter to the rocket.  There is no kick stage.

Conclusion: There is no kick stage.

Note:  That the FHe 6400kg payload capability can launch the Europa Clipper (6065kg) hence the additional capacity for the piggyback payload (273 kg).

So here's the payload sitting inside the Falcon's fairing:

 

Edited August 13, 2021 by jinnantonix