Pros and Cons, Dragon V2, CST-100 and Dream Chaser

[kerlc]

Has anyone mentioned that Dream Chaser's wings are not guaranteed to work all the time. Space Shuttle had wings too, and when Columbia's failed, the crew died.

Columbia "failed" when its TPS "failed". The wings had nothing to do with it. 

[vt_hokie]

Has anyone mentioned that Dream Chaser's wings are not guaranteed to work all the time. Space Shuttle had wings too, and when Columbia's failed, the crew died.

Columbia "failed" when its TPS "failed". The wings had nothing to do with it. 

I hate to play devil's advocate because most of you know I'm a lifting body shuttle proponent and spaceplane fan, but indeed the larger, more exposed, and likely more fragile (including numerous aero control surfaces as well as gear doors) TPS is something to consider, especially in the assured crew return vehicle role where the vehicle is exposed to potential debris impacts for 6 months while attached to ISS.

[hrissan]

What about the Dream Chaser's dry weight of 11300 vs Dragon's 4200 (according to wiki) with the same crew of seven.

If that is true, large CON to DC.

[veblen]

I left Orion out because it is not commercial crew. The following post is a good start I think.

One should also consider these options and consider if there is a realized advantage vs Soyuz and the cost savings...

Soyuz:
Pros:  Proven, safe, operational, affordable (... in other words <<< $1B/year)
Cons:  Requires astronaut training in another country.  Flight services may be ending by 2020 (could be continued).

Another con: Soyuz can carry 3 crew maximum plus some binders, food and small personal items for uphill ride to station. Commercial will fly up to 7 crew.

[meekGee]

What about the Dream Chaser's dry weight of 11300 vs Dragon's 4200 (according to wiki) with the same crew of seven.

If that is true, large CON to DC.

Does that include the LAS stage?

[Razvan]

I think, at this time all three have some pros, i.e.:

- CST-100  It is a robust vehicle and, given Boeing expertise and experience, a guaranteed success. It will definitely engage Boeing in the race of taking passengers around the Globe and farther...

- Dream Chaser is a pleasant and surely less costly alternative to the US Shuttle. It may offer attractive business cooperation to different industries;

- DV2 would become a versatile platform once its reusability is achieved. I am thinking this bird might be able to be launched from and landed to ocean oil platforms, atolls, carriers, etc. and fly around the Globe like a real live superfast Dragon...

[docmordrid]

What about the Dream Chaser's dry weight of 11300 vs Dragon's 4200 (according to wiki) with the same crew of seven.

If that is true, large CON to DC.

Does that include the LAS stage?

The DragonFly RLV draft EIS gives it a mass of 7,000 kg. How close that is to a real V2 is a point for discussion, but I propose it's a lot closer than the 4,200 kg number (which IIRC is for Dragon "V1".) For now perhaps we should assume at least 6,500 kg?

What "LAS stage"? DC and V2 have an integrated LAS, or are DC's hybrids too weak (the SS2 issue) for aborts?

[meekGee]

What about the Dream Chaser's dry weight of 11300 vs Dragon's 4200 (according to wiki) with the same crew of seven.

If that is true, large CON to DC.

Does that include the LAS stage?

The DragonFly RLV draft EIS gives it a mass of 7,000 kg. How close that is to a real V2 is a point for discussion, but I propose it's a lot closer than the 4,200 kg number (which IIRC is for Dragon "V1".) For now perhaps we should assume at least 6.500 kg?

What "LAS stage"? DC and V2 have an integrated LAS, or are DC's hybrids too weak (the SS2 issue) for aborts?

DCs built-in motors, IMO, can't give it a 5g kick for LAS.  Their thrust is probably public knowledge though.

[TrevorMonty]

All the engines and thrusters on the DC use non toxic propellants. The main engines are used for the abort.

 http://m.aviationweek.com/awin/sierra-nevada-pushing-ahead-dream-chaser

[meekGee]

My bad then, wrt DC abort.

[mike robel]

My try:

Here is my try, I am sure many will have diverging opinions:

Dragon V2 pros:
   - key components already flight proven (Draco, PICA-X, pressure shell, GN&C, water/parachute landing)
   - full vertical integration of the whole stack in the same company
   - redundant landing options (powered vs. parachute)
   - Elon Musk aura
   - reusable
   - significantly lower retrieval cost (in powered landing)
   - classic (proven) capsule design
   - lowest cost per mission (estimated up to 140 million)

Dragon V2 cons:
   - toxic hypergolics used
   - powered landing reduces usable mass to orbit
   - powered landing not proven

CST-100 pros:
  - conservative, low risk capsule design
  - Boeing as a proven provider
  - could switch launch vehicles (although not likely)

CST-100 cons:
  - higher (or even highest) cost per flight
  - boring

DC pros:
  - lifting body design, horizontal landing
  - reusable from the start
  - inspirational, airplane like
  - lowest G forces during EDL
  - can switch launch vehicles
  - cost effective for larger number of flights?

DC cons:
 - least proven design/highest risk
 - producer with least spaceflight heritage
 - might be locked to Atlas V
 - more expensive than Dragon?

Costwise I would predict the following:
  - Dragon V2 + F9R - 140mil per mission
  - CST-100 + Atlas V 401 - 250mil per mission
  - DC + Atlas V 401 - 200mil per mission

Why is CST-100 boring?

Because it's a capsule, so is dragon?
Because it uses parachutes, so does Dragon to date.
Because it lands on land with airbags?  Dragon to date lands at sea.
Because it's made by Boeing?   You may see boring, others may see (perhaps mistakenly, reliability.)

Or just because it is not Space-X of Sierra Nevada?

Actually, to me, CST-100 is an Apollo shaped Big Gemini.

[savuporo]

Okay, which one has the longest on orbit time ? Which one can be used as lifeboat ?
How many watts of power available for extra experiment equipment inside of cabin ? Volume and mass of potential mission equipment ? Extra downmass ?
Available Delta-V sans the rocket upper stage, i.e. how far can it get from it's insertion orbit ? Potential apogee height - can it go through van allen belts with a dedicated service module ?
Available ground comm link bandwidth ?

Dont know about anyones "aura" but these are sort of interesting parameters for comparable spacecraft, for me.

[TrevorMonty]

CTS100 is the least reusable of these vehicles ie
expendable service module, both parachutes and airbags have to be repacked or replaced.

The Dragon is not totally reusable as the trunk needs replacing but it will be considerable cheaper than CTS100 SM.

[edkyle99]

CST-100 cons:
  - boring

That may be a pro, rather than a con.  Remember that "boring" and "conservative" might be deemed "proven design type" and "low program risk" by NASA. 

Avionics is also important.  CST-100 is proposed to use Lockheed Martin Orion style avionics, installed and tested at KSC.  Dream Chaser flight controls looked like something that any pilot would already understand.  Dragon crew interface looked a bit "out there" by comparison, like nothing I've ever seen in a spacecraft.  NASA will need convincing.

 - Ed Kyle

[Darkseraph]

CTS100 is the least reusable of these vehicles ie
expendable service module, both parachutes and airbags have to be repacked or replaced.

The Dragon is not totally reusable as the trunk needs replacing but it will be considerable cheaper than CTS100 SM.

That's not a huge con. The amount of times this vehicle will be used is very small in the first place, given that extending the ISS past 2020 is already in doubt. The amount of crew rotations is very small, given that soyuz will be responsible for half the crew anyway and it only happens every 6 months roughly. If two companies are picked to do crew missions, there will be even less missions per vehicle.

[Prober]

CST-100 cons:
  - boring

That may be a pro, rather than a con.  Remember that "boring" and "conservative" might be deemed "proven design type" and "low program risk" by NASA. 

Avionics is also important.  CST-100 is proposed to use Lockheed Martin Orion style avionics, installed and tested at KSC.  Dream Chaser flight controls looked like something that any pilot would already understand.  Dragon crew interface looked a bit "out there" by comparison, like nothing I've ever seen in a spacecraft.  NASA will need convincing.

 - Ed Kyle

Experience Level

I'd add in the "experience" level into the mix.  Clearly, Boeing wins as the most experienced in building a HRS.

The other two companies don't reach that level they would fall into general SC level with SN the longest number of years building SC and SpaceX bringing up the tail end with only a few years.  Sorry but that is how it is.

Skin in the game one of the milestones listed in this prior down select is of concern.  We know what was listed at that time but we don't have access to any more info.   It's clear however the mission of transport to the ISS has become muddy.   Don't want to expand on it or the mods will freak.
 

[TrevorMonty]

CTS100 is the least reusable of these vehicles ie
expendable service module, both parachutes and airbags have to be repacked or replaced.

The Dragon is not totally reusable as the trunk needs replacing but it will be considerable cheaper than CTS100 SM.

That's not a huge con. The amount of times this vehicle will be used is very small in the first place, given that extending the ISS past 2020 is already in doubt. The amount of crew rotations is very small, given that soyuz will be responsible for half the crew anyway and it only happens every 6 months roughly. If two companies are picked to do crew missions, there will be even less missions per vehicle.

If ISS is only the destination you a correct. But if  we are considering other possible destinations with higher flight rates eg a  Bigelow Station,  then the extra  costs in reusing CST100 can make a difference.

[Darkseraph]

CTS100 is the least reusable of these vehicles ie
expendable service module, both parachutes and airbags have to be repacked or replaced.

The Dragon is not totally reusable as the trunk needs replacing but it will be considerable cheaper than CTS100 SM.

That's not a huge con. The amount of times this vehicle will be used is very small in the first place, given that extending the ISS past 2020 is already in doubt. The amount of crew rotations is very small, given that soyuz will be responsible for half the crew anyway and it only happens every 6 months roughly. If two companies are picked to do crew missions, there will be even less missions per vehicle.

If ISS is only the destination you a correct. But if  we are considering other possible destinations with higher flight rates eg a  Bigelow Station,  then the extra  costs in reusing CST100 can make a difference.

I'm assuming that the ISS is the only destination in the near future just to be on the safe side. I'd love if there was loads of places to go to in LEO, but not counting on it. I don't think NASA should count on it either when choosing, their focus should be 100% on just getting the mission they were tasked with accomplished.

For what its worth, I think Bob Bigelow is a bit of a loon. 50 million dollars as a prize to develop a crew carrier was too much faith in US industry to achieve miracles because its "private" and a "sector" . That amount of money wouldn't even buy you the launch vehicle and no one really bit on that. There's the old joke about how you become a millionaire in space exploration, start of as a billionaire!! 500 millions would have been a bit more realistic as a prize.

[luinil]

Why is CST-100 boring?

Because it's a capsule, so is dragon?
Because it uses parachutes, so does Dragon to date.
Because it lands on land with airbags?  Dragon to date lands at sea.
Because it's made by Boeing?   You may see boring, others may see (perhaps mistakenly, reliability.)

Or just because it is not Space-X of Sierra Nevada?

Actually, to me, CST-100 is an Apollo shaped Big Gemini.

That's not very fair to compare what will the CST-100 do to what the dragon is currently doing.
Either you compare what they both will be doing (so landing on land without chutes used for the Dragon), or what they are both doing now (nothing for the CST-100, and nothing for the Dragon V2 to be fair).

[Burninate]

IMO the main relevant features will be system mass, payload capability (internal/external), and eventual cost per launch.  The last one represents a superset of the differences in landing/recovery.

Relative to a NASA-designed crew capsule, these are all incredibly cheap.  Keeping all three until we have a better grasp of their utility, and the overlap with Orion's utility, and how they might interact with commercial manned space stations, seems wise.