BLEO capabilities for commercial LEO vehicles

[FinalFrontier]

This discussion has been cropping up repeatedly on  the SLS and other threads so I decided to start a dedicated thread for it. The discussion revolves around which capsules or planned commercial spacecraft have BLEO capabilities built in, as well as what constitutes these capabilities in commercial vehicle. There has been quite a bit of debate already so I will post in some of the discussion from other threads.

[FinalFrontier]

NASA may have had a monopoly but SpaceX's Dragon and Flacon 9 would not since it will have rivals.  Such as the CST-100 from Boeing+Bigelow and the Dream Chaser from SpaceDev flying on enhanced EELV.

There may be a monopoly in lunar landers, if someone gets round to making one.

I don't even think a lunar lander would have a monopoly I can think of two companies that might make a lunar lander.

Armadillo and Blue Origin simply because they're planning manned VTOL sub orbital vehicles.

A VTOL sub orbital vehicle has a lot in common with what you'd need for a lunar lander.

Then there's LM who might offer their DTAL lander adding a third company.

As for what SLS will be i think something along the lines of the Jupiter 130/246 or Shuttle-C is pretty much a given due to the lack of a large US built lox kerosene engine plus the time and budget constraints.


I think there will be two lunar landers vs one simply because for some missions you'd want a cheap light lander but for others you'd want a heavy lander.

The first would be along the lines of HLR and would be used for robotic,simple crew rotation, and scout missions.
 I can see Armadillo or Blue Origin building such a vehicle.
http://www.nss.org/settlement/moon/HLR.html

The other would be larger and probably would be something along the lines of DTAL or the Phoenix lander from LUNOX.
As that bis needed to land rovers, and hab modules.
http://www.nasaspaceflight.com/2006/09/lockheed-martin-lunar-landers-revealed/
http://www.nss.org/settlement/moon/LUNOX.html

[FinalFrontier]

The LEO space taxi's will not be capable of getting BLEO, and even if they physically could they would not be capable of protecting their human occupants from the radiation. In addition, they could not survive re-entry from some location outside LEO. Those are physical limitations that will *have* to be imposed on the commercial crew spacecraft in order to be lifted to orbit on a LV other than an HLV.

There is no decision to make - it is already made by the physical limitations of the spacecraft.

Um?  What?  You do know that Elon has talked repeatedly about how Dragon has been designed from the start with the intention of being upgradeable for use in lunar return missions.  Most of the mass of the Orion system that made it so big it needed Ares-I was the fact that it had a ton of propellant on board and didn't use depots.

You don't need an HLV to lift a BEO capable capsule...I'm not sure where you get this idea from.

~Jon

[FinalFrontier]

Hopefully these are some debate starters. Look forward to everyone's  thoughts.

[mr. mark]

Spacex has stated that the pica-x heatshield is currently capable of lunar return velocities. I'm not sure about other aspects of the Dragon capsule.

[pathfinder_01]

Spacex has stated that the pica-x heatshield is currently capable of lunar return velocities. I'm not sure about other aspects of the Dragon capsule.

With that ability it could support a BEO mission with both cargo and cargo return.

[alexw]

Spacex has stated that the pica-x heatshield is currently capable of lunar return velocities. I'm not sure about other aspects of the Dragon capsule.

A basic issue seems to be that both Orion and the Com. Crew capsules are poorly suited as true BEO vehicles -- from opposite ends of the spectrum.

Orion (classic) is a combination of a 4-person ascent/entry vehicle and a Lunar Transfer Vehicle (in the sense of an MTV). It's a design optimized for lunar surface; self-supporting; heavyweight; truthfully described as "Apollo on Steroids". That's not a good basis for BEO-> NEOs and Phobos, when we will need some kind of hab or MTV vehicle anyway.

Three different exploration plans -- Mars DRA5, HEFT, and ULA -- all envisioned a quite-different kind of Orion, removing most of the weight and capability of the service module, since the vehicle would not be flying solo.

The question is: is it easier and cheaper to largely reinvent Orion, stripping it down to a pure-er high-speed Entry (and possibly Ascent) capsule, or to build on Dragon, etc. to bring it up to that capability?

-Alex

[pathfinder_01]

Spacex has stated that the pica-x heatshield is currently capable of lunar return velocities. I'm not sure about other aspects of the Dragon capsule.

A basic issue seems to be that both Orion and the Com. Crew capsules are poorly suited as true BEO vehicles -- from opposite ends of the spectrum.

Orion (classic) is a combination of a 4-person ascent/entry vehicle and a Lunar Transfer Vehicle (in the sense of an MTV). It's a design optimized for lunar surface; self-supporting; heavyweight; truthfully described as "Apollo on Steroids". That's not a good basis for BEO-> NEOs and Phobos, when we will need some kind of hab or MTV vehicle anyway.

Three different exploration plans -- Mars DRA5, HEFT, and ULA -- all envisioned a quite-different kind of Orion, removing most of the weight and capability of the service module, since the vehicle would not be flying solo.

The question is: is it easier and cheaper to largely reinvent Orion, stripping it down to a pure-er high-speed Entry (and possibly Ascent) capsule, or to build on Dragon, etc. to bring it up to that capability?

-Alex

Imho it would be easier to strip Orion. That is why I view lifeboat orion as useful.  it was designed for BEO work from the get go. Dragon was designed with BEO in mind but currently is further from that goal.

My dream craft would be a pure lunar transefer vechile  but that requires getting large scale propellant transfer up and this is not likely to happen.

[ChefPat]

What, precisley, would it take to put the Bigelow Exploration [Station or Vehicle] (seen in this video at 3:38 & again at the end of the video  ) onto Low Mars Orbit?

[butters]

L2 is the most sensible staging point for Earth ascent/entry vehicles in the BEO exploration architecture.

LEO staging is inefficient because of the propulsive dV or aeroshell mass required to brake into LEO from the return trajectory, and SEP is problematic for crew because of the time spiraling through the Van Allen belt.

L1 is a close second, but the fast trajectory for crew from LEO costs more dV than the fast trajectory to L2 (even though L1 is a day or so closer), and L2 is considerably colder, which is ideal for staging propellant and parking vehicles at the depot.

So what we're talking about in terms of requirements for a BEO capsule is a round trip to L2 with extended docked time at an L2 depot that can supply power and station-keeping in a low thermal environment.

Depending on the the propulsion architecture, the capsule may not need to provide any propulsion of its own, only attitude control and not for the entire mission. On the other extreme, it may be required to insert into and depart from L2, which would entail roughly 700m/s (Dragon currently has about 550m/s).

Life support consumables are only necessary for the round trip to L2. Regenerative ECLSS systems are not really necessary. However, basic facilities such as galley and toilet are highly desirable for trips of this duration.

Additional radiation shielding may be required. I don't know enough to really comment specifically on this issue.

The capsule obviously has to be able to withstand atmospheric reentry from L2. My understanding is that this is not a problem for Dragon.

[pathfinder_01]

Dreamchaser XL(a larger version of dream chaser) could have BEO capability(lunar) depending on heat shield technology. The plan was to coat the tiles with an ablative. It would have a long reentry where it comes in upside down using the negative lift to keep the craft in the upper atmosphere to reduce velocity. Then it would turn upright and either go for a landing shuttle style or do a burn and head back to Orbit. From Orbit it would have more control over where it would land or allow for in space reuse via docking with another craft to head down to earth.  It is questionable if this is the best craft for the job but the thought is interesting.

A small bigleow inflatable connected to a propulsion module could travel back and forward from LEO to L1 if you could move about 40-50 tons of propellant to l1 or if you could de-crew it(via lightweight capsule) and use something like electric propulsion or an electro-dynamic tether to bring it down to LEO for servicing. 

In addition you could launch one in LEO, equip it at the  then send it to l1 using a centaur.

Boeing CST100 is strictly LEO but I could see Boeing leveraging the technology for a lunar model if pressed. Right now Boeing is basically doing what NASA should have (get to the ISS first then worry about the moon).  Unfortunately politics and the hope for a truly lunar program(instead of the funding farce that was cxp) caused Orion to get both heavy and expensive for the LEO mission.

Where commercial shines is in Cargo atm.

Cgynus and Dragon both could be easily sent to l1/l2 by EELV. Cygnus might even have an edge here due to being lighter weight despite the fact that it carries less. 2,000kg worth of cargo for 4 people could be quite a bit. It is about 3 months of food and water in 1 shipment for a crew of 4. Granted other stuff needed will cut into that time, but that 1 shipment of cargo could easily support 4 people for a month or two stay at l1/l2. It is the thermal and radiation differences at L1/L2 that could pose problems.

[beancounter]

Why are we trying to make existing transport capsules into space vehicles?
It seems to me that we should be specialising in distinct vehicles:  those that transport between Earth and say LEO and back, and those that move in space only.  I know that implies additional development and time but trying to make a single vehicle do both is the Shuttle experience all over again - you end up doing neither well and it costs you a fortune.
JM2CW.

[Robotbeat]

Why are we trying to make existing transport capsules into space vehicles?
It seems to me that we should be specialising in distinct vehicles:  those that transport between Earth and say LEO and back, and those that move in space only.  I know that implies additional development and time but trying to make a single vehicle do both is the Shuttle experience all over again - you end up doing neither well and it costs you a fortune.
JM2CW.

One of the main arguments is cost. If the LEO taxis already are almost capable of BLEO service and are much less expensive than the non-LEO-taxis while also being lighter (which ripples down throughout the whole stack), then there's a lot to be said with doing it that way, especially if you need a mission-module (or lander) anyways. *shrug* I'm undecided.

[hop]

Why are we trying to make existing transport capsules into space vehicles?
It seems to me that we should be specialising in distinct vehicles:  those that transport between Earth and say LEO and back, and those that move in space only.

Direct return tends to be more mass efficient than getting your deep space vehicle back into a LEO to meet an LEO only vehicle, even if it means lugging a heavy capsule all the way to your destination and back.

[butters]

Why are we trying to make existing transport capsules into space vehicles?
It seems to me that we should be specialising in distinct vehicles:  those that transport between Earth and say LEO and back, and those that move in space only.

I agree in principle, but LEO is not a very convenient place to stage between launch/reentry vehicles and dedicated spacecraft, because a substantial amount of dV is required, either propulsive or aerothermal, to insert the dedicated spacecraft back into LEO on the return trip. LEO is also a relatively severe environment in terms of radiative heating and drag effects that the dedicated spacecraft would not encounter in deeper space.

So I reiterate that EML1/2 are more sensitive staging points between Earth-bound vehicles and deep space vehicles. These points are not that far away in terms of time or velocity, and with an LEO depot, any upper stage capable of reaching LEO from a typical TSTO staging velocity is also capable of reaching EML with the same payload.

If you really want to park the reentry vehicle in LEO, then you really need at least three vehicles: the launch/reentry vehicle, the LEO/EML vehicle, and the space vehicle (lunar lander, mars voyager, etc.). That LEO/EML vehicle would be fairly difficult to develop unless it relies on lots of propellant delivered to EML.

It makes sense to eliminate the LEO/EML vehicle, because the launch/reentry vehicle can handle that role with less engineering complexity than an aerocapture design and far less mission mass than a propulsive design even considering the penalty of hauling the heatshield out to EML.

EDIT: hop made my argument a lot more succinctly.

[Gravity Ray]

Question for you all?

Wouldnt a Bigelow (double sundancer/ single BA330) with a docking/engine structure to tie them together be a better BLEO vehicle? In effect make your space ship a small station. Sitting in any capsule for days on end (or month for a Mars mission) seems very hard on the body to me.

[Ben the Space Brit]

Question for you all?

Wouldnt a Bigelow (double sundancer/ single BA330) with a docking/engine structure to tie them together be a better BLEO vehicle? In effect make your space ship a small station. Sitting in any capsule for days on end (or month for a Mars mission) seems very hard on the body to me.

I don't think that anyone is seriously talking about using an enhanced Dragon or other commercial vehicle for longer-duration flights than flights to EML or LLO.  Beyond that, some manner of hab module is needed, not simply for habitation space but also for extra consumables storage.

[pathfinder_01]

Question for you all?

Wouldnt a Bigelow (double sundancer/ single BA330) with a docking/engine structure to tie them together be a better BLEO vehicle? In effect make your space ship a small station. Sitting in any capsule for days on end (or month for a Mars mission) seems very hard on the body to me.

It would take months for a Mars mission and could take months for a NEO mission. For those missions a Mars transfer Vehicle or a habitat module would be a needed. Bigelow's modules would be very good at that.

However for those missions you would probably want to take a capsule along also. Direct reentry is the easiest method of returning to earth and his space station modules can't survive reentry. Having a capsule would be handy in case of abort.

For a trip to the moon(if it is short enough) or l1 a capsule could do. You could use a bigelow module for this but it would become a complication in an emergency. If needed a capsule can return directly to earth while if you used the module you would need to transfer to some other craft to handle reentry.

[A_M_Swallow]

Why are we trying to make existing transport capsules into space vehicles?
It seems to me that we should be specialising in distinct vehicles:  those that transport between Earth and say LEO and back, and those that move in space only.  I know that implies additional development and time but trying to make a single vehicle do both is the Shuttle experience all over again - you end up doing neither well and it costs you a fortune.
JM2CW.

As people above have said the simple answer is cost.  The big problem spacecraft designers have is that on machines purchased for millions of dollars transportation costs still exceed manufacturing costs.

Transportation costs are the costs of the vehicle plus propellant plus interest on the loan plus labour.  A quick summary follows.

Transportation costs increase by payload mass.  The increase is not linear but exponential.  No Shylock ever dared charged the usury rates of compound interest rates that spacecraft designers have to live with.

More payload mass means more propellant and a bigger rocket.  Propellant is fuel plus liquid oxygen (or other oxidant).  More propellant means bigger cost.  Bigger launch vehicle (rocket) means bigger cost.

A good estimate of the propellant needed can be calculated using the rocket equation
m0 = m1 * exp(delta_V /( g*Isp) )

Where
    m0 is the total mass at launch, including propellant, payload and LV.
    m1 is the final total mass.
    Isp is the specific impulse expressed as a time period
    Delta_v is the maximum change of speed of the vehicle (with no external forces acting)
    g is the acceleration due to Earth gravity 9.81 m/s/s

Units used for mass or velocity do not matter as long as they are consistent.

mass of propellant needed is m0 - m1

Conversion of propellant mass to cost by multiplying by the price/kg is an exercise for the student.

A table of Delta_Vs can be found on this web page.
http://en.wikipedia.org/wiki/Delta-v_budget


One method of cost savings has been discovered replacing the main landing thrusters and fuel by a heat shield and parachutes.
This works when returning to the Earth surface from LEO, EML1, EML2 and low lunar orbit (LLO).
Unfortunately NASA has not yet got aerocapture (heat shields) to work within a reasonable amount of time when returning to LEO.  Aerocapture has been used on a Mars trip but took 6 months which is considered unacceptable for human flights.

Until low cost manned aerocapture works reusable LEO-EML1/2 and LEO-LLO vehicles are not viable.

Solar Electric Propulsion (SEP) spacecraft with their high Isp can return to LEO but since the voyages taking about a year are not considered suitable for humans.

[A_M_Swallow]

Question for you all?

Wouldnt a Bigelow (double sundancer/ single BA330) with a docking/engine structure to tie them together be a better BLEO vehicle? In effect make your space ship a small station. Sitting in any capsule for days on end (or month for a Mars mission) seems very hard on the body to me.

Yes, if the Bigelow returns to EML1 rather than LEO.  At EML1 the astronauts could change to a capsule for the last part of the trip home.

[Hop_David]

Question for you all?

Wouldnt a Bigelow (double sundancer/ single BA330) with a docking/engine structure to tie them together be a better BLEO vehicle? In effect make your space ship a small station. Sitting in any capsule for days on end (or month for a Mars mission) seems very hard on the body to me.

I don't think that anyone is seriously talking about using an enhanced Dragon or other commercial vehicle for longer-duration flights than flights to EML or LLO.  Beyond that, some manner of hab module is needed, not simply for habitation space but also for extra consumables storage.

I see on Wikipedia Dragon will have TPS for re-entry return from the moon or even Mars. Does Elon plan radiation shielding sufficient for passage through the Van Allen belts? Any provision for EVAs?

I had thought Motorola sats and delivery of cargo to I.S.S. was the extent of SpaceX near term goals. And anything beyond LEO was Power Point. It's exciting that they seem to be already bending metal for beyond LEO.

[Robotbeat]

Radiation shielding from acute space radiation (i.e. SPEs) is pretty simple, to be honest. If more is needed, just add more mass (and not that much more, actually). No reason you couldn't install it inside the capsule on a later date. It'd be quite simple. (The Apollo command module was thick enough, so the astronauts would've just retreated there in case of a SPE... Dragon, once fitted for crewed service, might also be thick enough...)

For long-duration missions where chronic radiation exposure might be a concern, you're going to be spending almost all of your time in the mission module, so it doesn't matter as far as Dragon (or other commercial capsules) is concerned.

[docmordrid]

Speaking as someone with a radiation protection background.  Someone please chime in if my memory of structural details are amiss.

My understanding of the Apollo structure is that it had two concentric honeycombed hulls; the outer of thin steel, and the inner one of aluminum alloy.  The thinnest section was .25" in the aluminum hull and the thickest 2.5" in the steel section, most of both being empty space between 2 layers of thin metal.

In both cases most all of the protection from radiation coming in perpendicular to a given surface comes from the honeycombs inner and outer layers.  Non-perpendicular "incoming" would be attenuated a bit more, depending on the angle.

While these sheets, two each of aluminum and steel, would stop cold alpha, weak beta (electrons) and seriously attenuate lower energy x-rays/gamma, they are near useless vs. stronger x-rays, high energy electrons, protons or fast neutrons.  Not much would be effective against them without adding excessive mass.  Just stopping the weakest protons in the belts would require >.6mm of lead sheeting.

If Dragons pressure hull is also honeycombed aluminum alloy in structure and >2.5" thick (it appears to be at least that thick based on the pic of the COTS-2 hull) with thicker skins, then it could already be equal within practical limits to Apollo vs. perpendicular radiation.  If it's solid machined aluminum alloy and that thick, it's probably better than Apollo.

All else being equal the best protection is always reducing the exposure time, meaning in the case of spacecraft - speed. This would be most useful for going through the more energetic outer belt. The inner belt is where  ISS and LEO live, starting at 60 miles/100 km.

[Jim]

There is "spalling" effects and structure activation effects too.

[Ben the Space Brit]

I see on Wikipedia Dragon will have TPS for re-entry return from the moon or even Mars.

I'm assuming that this is referring only to a re-entry directly from return orbit.  The Dragon would be the CRV and maybe the command centre in such a mission but not the crew habitat.

[docmordrid]

There is "spalling" effects and structure activation effects too.

Aluminum gamma emissions from neutron activation run between .8347 and 1.368 mev. These will penetrate most hulls of the metals we're talking about, so unless you line the hull interior with lead, which alone could be toxic....

For Lithium + neutrons you mostly get stable Helium and Tritium, which decays to Helium 3 and a relatively weak electron, or Berillium-8 which decays into two alphas, none of which are going anywhere unless the reactions started in an inner walls surface.

For Compton scatter (spalling) effects from mid-energy gamma you get progressively weaker x-rays until the reaction becomes photoelectric, and at the levels >1mev it takes significant metal to attenuate it - much more than in Apollo.  Significantly higher energies add some electron-positron pair production.  The positrons decay when they hit matter with a mid-gamma emission and the electron is your basic beta particle.

Etc...

Bottom line is that several millimeters of aluminum, perhaps with some polyethylene, gives you about as much shielding as is practical for a capsule without driving the mass to impractical levels.  If you want better, attach a Bigelow hab.

[Jim]

There is "spalling" effects and structure activation effects too.

Aluminum gamma emissions from neutron activation run between .8347 and 1.368 mev. These will penetrate most hulls of the metals we're talking about, so unless you line the hull interior with lead, which alone could be toxic....

For Lithium + neutrons you mostly get stable Helium and Tritium, which decays to Helium 3 and a relatively weak electron, or Berillium-8 which decays into two alphas, none of which are going anywhere unless the reactions started in an inner walls surface.

For Compton scatter (spalling) effects from mid-energy gamma you get progressively weaker x-rays until the reaction becomes photoelectric, and at the levels >1mev it takes significant metal to attenuate it - much more than in Apollo.  Significantly higher energies add some electron-positron pair production.  The positrons decay when they hit matter with a mid-gamma emission and the electron is your basic beta particle.

Etc...

Bottom line is that several millimeters of aluminum, perhaps with some polyethylene, gives you about as much shielding as is practical for a capsule without driving the mass to impractical levels.  If you want better, attach a Bigelow hab.

Do some searches on "Shuttle activation monitor", it might interest you

[docmordrid]

I read Haskins, et al's paper about SAM on NIH's Pubmed long ago. 

It basically confirmed what radiation safety people have been taught for decades - more metallic shielding often results in a high flux of more absorbable "scattered" radiation. That's why we measure doses in terms of absorbed dose, not raw flux.  Radiographers are also familiar with this effect as it can impact image quality.

IMO this is exhitlbit "A" against those who claim that Dragon "needs" substantially more shielding to go on short to medium duration BLEO missions. 

No, what's needed is a small Bigelow type hab (thicker polymer walls are good at absorbing scatter) with a shelter area for solar events.  IIRC Bigelow has a patent on just such a shelter.

[Patchouli]

I read Haskins, et al's paper about SAM on NIH's Pubmed long ago. 

It basically confirmed what radiation safety people have been taught for decades - more metallic shielding often results in a high flux of more absorbable "scattered" radiation. That's why we measure doses in terms of absorbed dose, not raw flux.  Radiographers are also familiar with this effect as it can impact image quality.

IMO this is exhitlbit "A" against those who claim that Dragon "needs" substantially more shielding to go on short to medium duration BLEO missions. 

No, what's needed is a small Bigelow type hab (thicker polymer walls are good at absorbing scatter) with a shelter area for solar events.  IIRC Bigelow has a patent on just such a shelter.

Apollo did not really have much in the way of dedicated radiation shielding.
The CSM mostly depended on it's normal structure and the propellant in the SM for shielding.
The LEM had some panels coated with a special radio-luminescent paint and some thin acrylic sheets for shielding soft X-rays.
http://www.informantnews.org/modules.php?name=Content&pa=showpage&pid=10

Dragon and DreamChaser in this aspect might be better off then Apollo was.
Dragon has several large propellant tanks at the base a lunar variant likely also would have propellant tanks in the trunk.
Dream Chaser is even better equipped because of it's composite pressure hull and the placement of the hybrid propulsion system.

The CST-100 would likely just do what Apollo did place the SM between it and the sun during a solar storm.

It's close enough to Apollo it might even be possible to use some of the old Apollo data.

[Jim]

I read Haskins, et al's paper about SAM on NIH's Pubmed long ago. 

I was their launch site support while in the USAF

[moose103]

Good talk by docmordrid and Jim.

Since excellent protection (an ocean of molecules) is much more expensive than just "good" protection, the best way to go is bunk beds in the propellant tanks.

[alexw]

Good talk by docmordrid and Jim.
Since excellent protection (an ocean of molecules) is much more expensive than just "good" protection, the best way to go is bunk beds in the propellant tanks.

   Or polyethylene, or other hydrogen-rich material. Paraffin. Hey, add some LOX, and people could travel safely in giant wax candles in space! (Why does this remind me of Ares I?)

   More seriously, does this suggest a lighter capsule to hightail it to EML2 where the hab is waiting? To what extent are (rapid) T-EML2-I trajectories' elapsed time sensitive to delta V, and are there additional requirements on the insertion burn at L2?
    -Alex

[ChefPat]

I read Haskins, et al's paper about SAM on NIH's Pubmed long ago. 

I was their launch site support while in the USAF

Damn it Jim, your an Engineer not a Doctor!!!

[Patchouli]

Good talk by docmordrid and Jim.

Since excellent protection (an ocean of molecules) is much more expensive than just "good" protection, the best way to go is bunk beds in the propellant tanks.

If they ever build a BLEO capable version of Dream chaser one safest places to be in a solar storm might be in the back of the vehicle.

N2O and HTBP is not the best radiation shield but you'd have a few tons of it.

Maybe put the water and O2 tanks in the ceiling and floor and you'd have a fairly complete shelter for nearly free cost in mass.

A smart move if you're docked to a Bigelow module would be to keep the crew vehicle between the module and the sun during a solar storm.

A hydrogen propellant depot could make one of the best storm shelter's possible.

[Robotbeat]

Actually, a methane depot, for the same volume, would be a lot better than the hydrogen depot. (EDIT: As far as radiation shielding is concerned... Same probably goes for other hydrocarbons.)

[docmordrid]

Probably so, just as long as you can keep it >91°K.