Author Topic: Are Commercial Crew Vehicles Usable/Upgradeable for Beyond-LEO Needs?  (Read 60987 times)

Offline manboy

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This question came up on a different thread, so I thought I would start a specific one to collect everyones thoughts.

The subject came up when I responded to a statement from Robotbeat:

I will say one thing: since both designs chosen were capsules, they are both relevant for any future BLEO missions and should be considered for inclusion by mission planners.

None of these vehicles will be evolved for BLEO - they are too small.  Be glad to talk on another thread about it if you want...

A number of people agreed with Robotbeat, or at least with the idea that Commercial Crew vehicles could be adapted for beyond LEO needs.

My reasons for saying that Commercial Crew vehicles are too small is that I think we have learned that for humans to stay healthy in space that they need a lot of room, so future human space travelers are not going to be spending most of their time in a capsule like the Dragon or CST-100.  Plus, capsules are really only designed for transporting humans to/from a planet with an atmosphere, so at most my view is that if we take them BEO it's only for use as a lifeboat and for the "last mile" of getting humans down onto a planet.  And currently the only planet we know we can land them as currently designed is Earth, so why not leave them orbiting in LEO and just plan to meet back up with them in Earth orbit on the way back?

If you think Commercial Crew vehicles will be adaptable for BEO applications, please state what those applications are.  For instance, would you envision using a CST-100 for visiting an asteroid or only for trips to the Moon?

And if you don't think they are applicable, go ahead and state what your alternative would be.
They probably would need new avionics if you send them BEO. Heat shield may need to be modified.
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Offline mmeijeri

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Beyond LEO is not the same as beyond earth orbit (BEO). I think the commercial crew vehicles are mostly useful for near Earth space and the last mile, but unlike Ron I think an important part of the action will be at L1/L2, in support of lunar and BEO missions, without actually going there. That is beyond LEO, but not BEO.

Then again, Red Dragon suggests there might be a role for Dragons on Mars too.

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Online Robotbeat

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A lot of Mars architectures nowadays (that I've seen internal at NASA, plus that one Boeing proposal at FISO) propose leaving Orion at EML1/2 or some high lunar (or Earth, I suppose) orbit, just like where you'd leave Dragon or CST-100.
« Last Edit: 10/12/2014 09:13 PM by Robotbeat »
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Offline WindyCity

Forgive me if this has been already discussed.

Could a BA330 be mated with a Dragon 2 for BEO missions? I don't know what additional ECLSS would have to be added, but from what I've read, the radiation and meteorite shielding of the hab would appear to be adequate for travel in deep space. Also, the BA330 has a propulsion system. Could the hab be stationed in LEO and then hooked up to the crew capsule and then boosted onto an interplanetary trajectory?

That is basically what the BA-330 is designed for... and the propulsion system is a 'tug' that moves the entire bit beyond LEO... or beyond whatever location (EML-1/2 for instance).  I've not actually heard mention or seen written text that showed docked vehicle like Dragon 2 being accelerated with the BA-330, so the stresses at docking mechanism may be be limiting.

Great Article on the topic:
http://www.nasaspaceflight.com/2014/02/affordable-habitats-more-buck-rogers-less-money-bigelow/

Thanks!

Quote
Family of Tugs:

The documentation also portrays a family of tugs that could be used in conjunction with Bigelow habitats for use beyond Low Earth Orbit.

The fleet consists of the Standard Transit Tug, the Solar Generator Tug, the Docking Node Transporter and the Spacecraft Capture Tug.

These tugs could be used to push the various Bigelow Habitats – and other payloads – to specific destinations in LEO, L2, Cislunar space and beyond.

The four tugs are designed to be grouped together in various combinations, depending on the mission requirements. Notably, they are sized for launch on SpaceX’s Falcon Heavy rocket.

The tugs could be launched independently, prior to rendezvous with other elements in LEO to form a complete transport system. Each of these tugs share propulsion, docking and avionic systems.

Could they be parked in LEO and refueled as needed?

Quote
The BA 330-DS:

The documentation also offers NASA a deep space version of its habitat, the BA 330-DS, for use beyond Low Earth Orbit. The BA 330-DS could be used by NASA, for example, at a Lagrange point or in lunar orbit.

The BA 330-DS would be very similar to its LEO version. The main difference would be related to radiation shielding.

What additional shielding would it need. It already has a water jacket to protect against cosmic rays and solar radiation.

Offline docmordrid

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>
What additional shielding would it need. It already has a water jacket to protect against cosmic rays and solar radiation.

Bigelow has always said peripheral water containers, which would be a good shield.  A few extra points if you add soluble boron compounds (boric acid is soluble to 57g/l @25°C) as they'd enhance neutron protection, at the cost of potability.
« Last Edit: 10/13/2014 08:38 AM by docmordrid »
DM

Offline AncientU

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Could they be parked in LEO and refueled as needed?


What additional shielding would it need. It already has a water jacket to protect against cosmic rays and solar radiation.

'Tugs' has usually referred to in-space vehicles that are repeatedly refueled and reused.  I suspect this is the operational intent here.

The BA-330 radiation shielding may already contain a thermal neutron absorber, if one is actually needed.  Borated poly layers or boron in solution as proposed by docmordrid should be simple additions.  Bigelow statements have commented on the reduced amount of secondary radiation resulting from their soft-sided designs over aluminum cans.  Since free neutrons are mostly secondary radiation (cosmic rays, even from the sun, allow sufficient time for free neutrons --'primary radiation' -- to radioactively decay, even accounting for the relativistic effects of solar plasmas), and the rad dose from neutrons on ISS isn't too high, I suspect that this is mostly a solvable problem.  More empirical data is needed from operations beyond the Van Allen radiation belts.  An outpost at EML-2 would do nicely...

Here's an ISS experiment that showed neutron rad exposure to be (only) 10x the normal ground dose at sea level.  (This is about what moving to Denver from sea level also contributes.)
Quote
The average dose-equivalent rate observed through the investigation was about 10 times the average exposure on Earth.

http://www.nasa.gov/mission_pages/station/research/experiments/227.html
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Offline metaphor

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It takes about 600 m/s to capture at L1, or to leave L1 for Earth, with a travel time of about 5 days each way.  So any capsule will have to carry an additional 1200 m/s of delta-v over what it receives from the launch vehicle.  At 320s Isp, that means about 50% extra mass in propellant.

For L2 it takes about 350 m/s one-way with a ~9 day travel time.  So that's an extra 700 m/s, which at 320s Isp means about 25% extra mass in propellant.

That's a significant amount of extra mass needed if going to a Lagrangian point and back.

Offline A_M_Swallow

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It takes about 600 m/s to capture at L1, or to leave L1 for Earth, with a travel time of about 5 days each way.  So any capsule will have to carry an additional 1200 m/s of delta-v over what it receives from the launch vehicle.  At 320s Isp, that means about 50% extra mass in propellant.

For L2 it takes about 350 m/s one-way with a ~9 day travel time.  So that's an extra 700 m/s, which at 320s Isp means about 25% extra mass in propellant.

That's a significant amount of extra mass needed if going to a Lagrangian point and back.

The mass is propellant so it can become the cost of propellant in LEO V. cost of a new spacecraft in LEO.
Reusable launch vehicles can make a big price difference to that trade.

Offline mmeijeri

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That's a significant amount of extra mass needed if going to a Lagrangian point and back.

Orion is supposed to have ~1.6 km/s in delta-v, so I don't see any problem with that.
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Offline metaphor

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That's a significant amount of extra mass needed if going to a Lagrangian point and back.

Orion is supposed to have ~1.6 km/s in delta-v, so I don't see any problem with that.

Well yeah, that's why the service module is there.  A commercial crew vehicle would need upgrades like that, that would make it heavier and costlier, in order to go BLEO.  In the end it would probably end up somewhat similar to Orion.

Offline pathfinder_01

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Given that NASA is using ESA to build the service module for Orion, I rather doubt they would be as bad as Orion esp.  as they could do LEO runs as well as BEO trips.

Offline MP99



It takes about 600 m/s to capture at L1, or to leave L1 for Earth, with a travel time of about 5 days each way.  So any capsule will have to carry an additional 1200 m/s of delta-v over what it receives from the launch vehicle.  At 320s Isp, that means about 50% extra mass in propellant.

For L2 it takes about 350 m/s one-way with a ~9 day travel time.  So that's an extra 700 m/s, which at 320s Isp means about 25% extra mass in propellant.

That's a significant amount of extra mass needed if going to a Lagrangian point and back.

Imagine a SpaceX architecture which uses EML2 as a terminus for an MTV.

If you can line everything up on the return from Mars, you only need an Oberth-assisted ~1 km/s burn at perigee to capture in Earth's gravity and "TLI" towards the Moon. (With MAC you can possibly do it almost prop free via aerocapture.) Another 350 m/s at EML2, and you're done.

For the next outgoing trip to Mars, the MTV only needs a 350 m/s departure burn + ~1 km/s Oberth-assisted TMI, to achieve a TMI that would need a 4.2 km/s burn from LEO.

I suspect that an architecture that needs ~1.7 km/s for the complete Earth turnaround compares fairly well with a cycler. It's like putting an airport at the top of a mountain. Plane lands on an uphill runway, and stops without needing brakes, then takes off downhill without needing engines to reach takeoff speed. The Moon stores a lot of dV.



So, then, what's the cost of getting people & cargo to EML2, then on to Mars?

A 4.2 km/s TMI can either be done in one burn from LEO, or ~3.2 km/s TLI + ~1 km/s post-EML. No advantage here, but no disadvantage, either.

For MTV prop and other "storables", a three-month "slow-boat" / WSB trajectory gets you to EML for ~3.2 km/s. The total dV to get from Earth surface to TMI is about 400 m/s more than the simple launch / LEO / TMI.



Tl;dr - yes, crew and time-critical cargo needs ~700 m/s more dV to reach TMI if you stage from EML2, but the overall architecture gains a lot of mass advantages, such as MTV prop tanks being nearly 3 km/s smaller, and prop delivered in high mass fraction tankers.

Cheers, Martin

Offline mmeijeri

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Given that NASA is using ESA to build the service module for Orion, I rather doubt they would be as bad as Orion esp.  as they could do LEO runs as well as BEO trips.

Yeah, and that's why it would have made more sense for NASA to drop the capsule and to "outsource" it to commercial crew and to continue work on the SM, rather than outsourcing that to ESA.
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Online Robotbeat

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That's a significant amount of extra mass needed if going to a Lagrangian point and back.

Orion is supposed to have ~1.6 km/s in delta-v, so I don't see any problem with that.

Well yeah, that's why the service module is there.  A commercial crew vehicle would need upgrades like that, that would make it heavier and costlier, in order to go BLEO.  In the end it would probably end up somewhat similar to Orion.
SINCERELY doubt it could be as expensive as Orion. The capsule dry mass is far less for Dragon and cst100, just to name one thing.

Besides, if you take a 16 day trip instead of 5, the capture delta-v drops to ~195m/s, 390 total. Both probably have that capability just from abort propellent.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline mmeijeri

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SINCERELY doubt it could be as expensive as Orion. The capsule dry mass is far less for Dragon and cst100, just to name one thing.

Even if it were as expensive as Orion, it would still be cheaper than having two commercial crew capsules plus Orion. It would also be cheaper for LEO operations and available to commercial clients. More bang for fewer bucks.
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Offline TomH

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It's like putting an airport at the top of a mountain. Plane lands on an uphill runway, and stops without needing brakes, then takes off downhill without needing engines to reach takeoff speed.

Hey, I know that airport. Never been there, but as a former backpacking/climbing fanatic, I've read about it a number of times:

http://www.weather.com/travel/mount-everest-airport-will-terrify-you-photos-20130618

Had several daredevil pilots in the family too. Flew in and out of some places almost that scary with my dad.
« Last Edit: 10/14/2014 04:21 PM by TomH »

Offline nadreck

It's like putting an airport at the top of a mountain. Plane lands on an uphill runway, and stops without needing brakes, then takes off downhill without needing engines to reach takeoff speed.

Hey, I know that airport. Never been there, but as a former backpacking/climbing fanatic, I've read about it a number of times:

http://www.weather.com/travel/mount-everest-airport-will-terrify-you-photos-20130618

Had several daredevil pilots in the family too. Flew in and out of some places almost that scary with my dad.
I flew into and out of Lukla, note that you do need brakes and the rock wall coming at you as your Twin Otter lands is almost as scary as hoping that the plane actually has enough speed to stay airborne as it goes off the end of the runway on surface effect. Oh and the girl in the pink floppy hat sitting behind you throwing up is just a courtesy detail to make it all seem the more real. About 7 minutes before landing the plane passes between two peaks (not above them).
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline sdsds

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A 4.2 km/s TMI can either be done in one burn from LEO, or ~3.2 km/s TLI + ~1 km/s post-EML. No advantage here, but no disadvantage, either.

Your analysis is spot on, but I think truth is even better than you suggest. There are paths to EML which combine a chemical burn for LEO departure with electric propulsion to transfer onto the EML-bound trajectory. So looking at required IMLEO, utilizing the amazingly high isp of electric propulsion for a portion of the transfer to EML can be a meaningful win.

I believe this is less true for DRO, but haven't myself done the required math.  :D

In either case, rendezvous in the cis-lunar vicinity before departure for Mars has huge mission safety advantages, because abort modes are more accessible. (With classic TMI, you have to look at each moment of a long Earth departure burn and verify there's a safe abort in case of a propulsion failure. With TMI post-EML, the burn -- and thus the vulnerability -- is shorter.)

This all leads to the conclusion that EML (or DRO) rendezvous will be the Mars mission mode that one day is actually selected. Commercial crew and cargo to that rendezvous point are in the cards ... sooner or later depending on the stubbornness of those who refuse to admit it.
« Last Edit: 10/15/2014 03:40 AM by sdsds »
-- sdsds --

Offline MP99



A 4.2 km/s TMI can either be done in one burn from LEO, or ~3.2 km/s TLI + ~1 km/s post-EML. No advantage here, but no disadvantage, either.

Your analysis is spot on, but I think truth is even better than you suggest. There are paths to EML which combine a chemical burn for LEO departure with electric propulsion to transfer onto the EML-bound trajectory. So looking at required IMLEO, utilizing the amazingly high isp of electric propulsion for a portion of the transfer to EML can be a meaningful win.

Thanks.

With a Weak Stability Boundary (slow boat) trajectory, you need no propulsion to slow into EML - interaction of Earth / Moon / Sun does it for free (at expense of a three month transit).

Note that those dVs assume a full Oberth benefit. The two TMI burns totalling ~1.4 km/s give you ~4.7 km/s transit velocity, which eats into the SEP advantage.

Alternatively, such an "almost at escape already" orbit is far and away the best location from which to launch SEP, if you're going to use that for the transit.

I believe this is less true for DRO, but haven't myself done the required math.  :D

In either case, rendezvous in the cis-lunar vicinity before departure for Mars has huge mission safety advantages, because abort modes are more accessible. (With classic TMI, you have to look at each moment of a long Earth departure burn and verify there's a safe abort in case of a propulsion failure. With TMI post-EML, the burn -- and thus the vulnerability -- is shorter.)

This all leads to the conclusion that EML (or DRO) rendezvous will be the Mars mission mode that one day is actually selected. Commercial crew and cargo to that rendezvous point are in the cards ... sooner or later depending on the stubbornness of those who refuse to admit it.

The dV stuff is rather off topic, except insofar as I was using the above to justify why the relatively small dVs to enter / exit EML are well worth including in the baseline for any BLEO version of a LEO capsule, as an integrated part of a wider architecture.

Cheers, Martin

Offline mmeijeri

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So looking at required IMLEO, utilizing the amazingly high isp of electric propulsion for a portion of the transfer to EML can be a meaningful win.

Not only that, but transport of propellant (and eventually cargo) from L1/L2 to HMO and LMO can also be done with SEP, and that's easier given that it doesn't involve crossing the van Allen belts.
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