Author Topic: Are Commercial Crew Vehicles Usable/Upgradeable for Beyond-LEO Needs?  (Read 47294 times)

Offline AncientU

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As long as a fuel distribution network is established first, commercial crew vehicles plus in-space habs/tugs can do it all.  This is likely the reason the anti-depot crowd is adamant in opposition.
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Offline Robotbeat

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I don't know I agree. People are still very skeptical about commercial crew, think that ONLY the "big boys" can do it, and at ridiculous cost and about half a century's worth of time.
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Offline mmeijeri

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As long as a fuel distribution network is established first, commercial crew vehicles plus in-space habs/tugs can do it all.  This is likely the reason the anti-depot crowd is adamant in opposition.

You don't need to establish depots first, a spacecraft can act as it own depot just as ISS and Russian stations before it have been doing for decades.
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Offline AncientU

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As long as a fuel distribution network is established first, commercial crew vehicles plus in-space habs/tugs can do it all.  This is likely the reason the anti-depot crowd is adamant in opposition.

You don't need to establish depots first, a spacecraft can act as it own depot just as ISS and Russian stations before it have been doing for decades.

Doesn't really matter what you call it... when you have refueling technology on the (reusable) vehicles and the means to distribute fuel/refuel where and when you need it, you're good to go.  Anywhere.

The opposite is the concept that every drop of fuel for the entire mission needs to go into the stack before someone lights the fuse.  Expendable is a corollary concept.  I think we're finally ready to drive stakes through the heart of these undead beings.

Not everyone yet has the word...

Quote
There is still no significant move within NASA towards reusable spacecraft, or even boosters, while other institutions like the Air Force and DARPA are now pushing rapidly in that direction. Funding for propellant depots is virtually nonexistent, and any refueling efforts are aimed primarily at refueling and servicing existing satellites that were never designed to be refueled. Taking another look at this document, five years after its initial release, can give us a precautionary view of where not to go in space (and Mars) mission design.
emphasis mine

http://www.thespacereview.com/article/2618/1
« Last Edit: 10/15/2014 04:39 PM by AncientU »
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Offline mmeijeri

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Doesn't really matter what you call it... when you have refueling technology on the (reusable) vehicles and the means to distribute fuel/refuel where and when you need it, you're good to go.  Anywhere.

Exactly, but my point is that we've had the necessary technology for years. If NASA wants to build a transfer stage, let them start with a refuelable SM and leave launch vehicles and capsules to the market by buying services competitively. Later that SM can be enlarged to a storable L1/L2 based pump-fed transfer stage for manned exploration.
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Offline AncientU

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Doesn't really matter what you call it... when you have refueling technology on the (reusable) vehicles and the means to distribute fuel/refuel where and when you need it, you're good to go.  Anywhere.

Exactly, but my point is that we've had the necessary technology for years. If NASA wants to build a transfer stage, let them start with a refuelable SM and leave launch vehicles and capsules to the market by buying services competitively. Later that SM can be enlarged to a storable L1/L2 based pump-fed transfer stage for manned exploration.

Yup. Couldn't have said it better.

It's not a technology but a turf issue.
« Last Edit: 10/15/2014 05:00 PM by AncientU »
"If we shared everything [we are working on] people would think we are insane!"
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Offline RanulfC

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I don't know I agree. People are still very skeptical about commercial crew, think that ONLY the "big boys" can do it, and at ridiculous cost and about half a century's worth of time.

My take is that most people are 'skeptical' about commercial crew for the same reason; If "commercial" can do orbital travel then why is NASA insisiting on building the SLS?

Which to me pretty much hits spot on why Congress both encourages that thinking and why Commercial Crew is having such a hard time being taken seriously.

IF (and again there is that huge two letter word) you understand the facts its pretty clear that once you have an ongoing ability to transfer crew and supplies TO Low Earth Orbit on a regular basis while you still have incentive to build and operate an HLV you don't REQUIRE the ability to do so on a regular basis. I do NOT want to decend into that debate however and am simply pointing out that what is mostly being said is that SLS is "required" while CC is not and that's actually just the opposite of what it true. SLS is in fact "required" because its a government program while CC is "required" for lower cost, regular access to space by people. There's justification for both but instead both are being played off against each other.

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From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline guckyfan

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Can Dragon 2 do a lunar orbit mission without modified propulsion?

We know a lunar flyby with Dragon and FH is possible. The upper stage even would have enough delta-v for LOI but it won't last long enough without significant modification if at all. The idea is finding a TLI trajectory that minimizes LOI delta-v at expense of more delta-v for TLI. I am sure some modifications are possible but is it enough? It would not need a circularized lunar orbit. Just an elliptical orbit that would be easy to leave for trans earth injection too. It is not something one can take out of a delta-v map. But with plenty of abort fuel and a not so heavy Dragon is it achieavable? Ideally with enough fuel for a propulsively assisted parachute land landing.

Such an orbit may not be suitable for research but would be appreciated as a tourist flight.

Edit: The idea behind this is that SpaceX may not be willing to do major engineering for a modified Dragon but willing to sell a flight for a tourist operator.
« Last Edit: 11/24/2014 09:28 AM by guckyfan »

Offline baldusi

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You not only need Delta-v to get to a lunar orbit, but you also need to get back. Both Orion and PTK-L have 1,500m/s of delta-v. You can't get to. LLO without some serious burn close to the Moon. Now, if you wanted to do something like the orbit you get when you move from EML1 towards the moon, that might be different. You'd still need astrogation, long range coms, ECLSS, heat management and radiation resistance and mitigation for the crew.

Offline Zed_Noir

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Can Dragon 2 do a lunar orbit mission without modified propulsion?

We know a lunar flyby with Dragon and FH is possible. The upper stage even would have enough delta-v for LOI but it won't last long enough without significant modification if at all. The idea is finding a TLI trajectory that minimizes LOI delta-v at expense of more delta-v for TLI. I am sure some modifications are possible but is it enough? It would not need a circularized lunar orbit. Just an elliptical orbit that would be easy to leave for trans earth injection too. It is not something one can take out of a delta-v map. But with plenty of abort fuel and a not so heavy Dragon is it achieavable? Ideally with enough fuel for a propulsively assisted parachute land landing.

Such an orbit may not be suitable for research but would be appreciated as a tourist flight.

Edit: The idea behind this is that SpaceX may not be willing to do major engineering for a modified Dragon but willing to sell a flight for a tourist operator.

Just stick a Super Draco and lots of hypergolic tanks in the trunk. But like Baldusi posted. you need longer duration ECLSS, long range communication, navigation and ground tracking & Communication network (NASA is not going to provide the DSN time).

For tourism, think a free return orbit like Apollo 8 is all that is required initially.

Offline Robotbeat

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A really, really high lunar orbit (or EML2) is probably feasible without extra propulsion (may need some light-weighting, however), if you're willing to do a week or two trip time to the Moon's vicinity.

There's no "just" about adding a hypergolic stage or service module. (and you wouldn't use Superdracos, they have really crappy Isp and far more thrust than needed... instead, use an array of regular Dracos). It'd be a significant endeavor. Of course it could be done, but it wouldn't be free.
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Offline TrevorMonty

The CST100 modular design means they could use a large propulsion/service module for BLEO missions.
« Last Edit: 11/25/2014 02:31 AM by TrevorMonty »

Offline Patchouli

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Just stick a Super Draco and lots of hypergolic tanks in the trunk. But like Baldusi posted. you need longer duration ECLSS, long range communication, navigation and ground tracking & Communication network (NASA is not going to provide the DSN time).

For tourism, think a free return orbit like Apollo 8 is all that is required initially.


Instead of a Super Draco you'd probably be better off modifying the Kestrel engine from Falcon 1 to be hypergolic.
 This is not as crazy as it sounds as Aerojet did just that with the LR-87.
The Kestrel is a simple pressure fed engine and would be easy to modify for a different  propellant.


As for the CST-100 and Dream Chaser I'd look into just using the AJ-10 and a stage derived from the Delta-K or better yet the Titan Transtage.

A really, really high lunar orbit (or EML2) is probably feasible without extra propulsion (may need some light-weighting, however), if you're willing to do a week or two trip time to the Moon's vicinity.

There's no "just" about adding a hypergolic stage or service module. (and you wouldn't use Superdracos, they have really crappy Isp and far more thrust than needed... instead, use an array of regular Dracos). It'd be a significant endeavor. Of course it could be done, but it wouldn't be free.

True but you'll either need a resource module or to cut the crew size down.

« Last Edit: 11/25/2014 03:04 AM by Patchouli »

Offline Robotbeat

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I'm CONFIDENT that this is at least the tenth time this has been discussed.
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Offline guckyfan

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I'm CONFIDENT that this is at least the tenth time this has been discussed.

I believe you are right. I tried to avoid that by very specifically stating I am looking for a solution without modifications of propulsion. And if that is not possible just forget about it.

Offline Robotbeat

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I'm CONFIDENT that this is at least the tenth time this has been discussed.

I believe you are right. I tried to avoid that by very specifically stating I am looking for a solution without modifications of propulsion. And if that is not possible just forget about it.
It is possible.
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Offline Vultur

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For tourism, think a free return orbit like Apollo 8 is all that is required initially.

I agree.


Space Adventures is trying to sell a circumlunar trip at $150 million/seat. I wonder how cheaply SpaceX could provide that, assuming successful first stage reuse and reuse of the Dragonv2?


What would have to be modified to make Dragon capable of a lunar free return?

Offline A_M_Swallow

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I'm CONFIDENT that this is at least the tenth time this has been discussed.

July 2017. Now for the 11th time.

The transfer stage used to go from a LEO spacestation to the lunar orbit spacestation could be launched on a second launch vehicle. The capsule and transfer stage would be docked at the LEO spacestation.

Unless it can reenter with the capsule the transfer stage would probably be expendable, return to LEO requires too much propellant.

Offline GWH

How anyone GETS to the lander though is anyone's guess.

Some Dragon or CST-100 type vehicle?

Yeah one would probably be better off discussing that in more detail here: https://forum.nasaspaceflight.com/index.php?topic=35787.100

Probably wouldn't be quick and easy. Starliner is limited to 60 hour free flight, Dragon at least lacks the dV, and is a tight ride.  ....
False, on both accounts. And yeah, you should have discussed it in that thread.

Moving this over to the proper thread. 

Please elaborate on your "Jim-esque" reply, as it is contrary to information that I have seen and would like to know more.

Regarding Starliner:
Quote from: Nasaspaceflight.com
At most, Mr. Ferguson stated his desire for Starliner to employ 24-hour launch to docking profiles – due in part to the vehicle’s design, which limits its free flight capability (from launch to docking and then undocking to landing) for an entire mission to just 60 hours.
https://www.nasaspaceflight.com/2017/07/starliner-milestones-ula-switches-atlas-booster-maiden-flight/

Dragon 2, from information I have found, has a dry mass of 6,350 kg and carries a total prop mass of 1815 kg including the abort propellant. 
At an ISP of 300s for the Draco thrusters that's 0.74 km/s bone dry no payload.  Well short of returning from anywhere other than L2.
Now adding a kick stage of sorts or trunk based propulsion is well within possibility, but not within the scope of the vehicle as designed.
« Last Edit: 07/28/2017 06:10 PM by GWH »

Offline Robotbeat

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And why not stage from L2? The gateway will be in a similar energy orbit.

Just because Apollo used LLO doesn't mean that we should or that it's ideal. Even Orion cannot use LLO unless it leaves LEO with a lander (or similar) attached, which tends to necessitate an expendable lander.

I think EML1,2, or a similar energy orbit would be more appropriate for staging as we already have multiple current or near-term vehicles that would be capable of reaching it with minimal modifications (Orion, Dragon, Starliner, Soyuz, possibly even Shenzhou, on top of SLS, Falcon Heavy, Vulcan Heavy or Vulcan with distributed lift, New Glenn, two launch Delta IV Heavy, Proton/Angara, Long March 5, etc).

As far as having enough room, Gemini was tiny and the two astronauts spent 2 weeks in LEO. 3 or so days transit (longer for a more efficient trajectory) is not a huge constraint. Dragon has much more room per crew than Gemini. Plenty for cislunar. Same with Starliner.

Also, LLO is terrible for staging anywhere but the Moon.
« Last Edit: 07/28/2017 11:48 PM by Robotbeat »
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