Author Topic: NASA finally sets goals, missions for SLS - eyes multi-step plan to Mars  (Read 35035 times)

Offline john smith 19

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With the long time delay it looks like the government is dragging its feet waiting for commercial launch vehicles to become available. Commercial has the potential to reach the Lunar surface  and mars surface before SLS.

The economics with SLS are not there and now even more with 1st stage reuse. Congress and NASA needs to face reality !
I think you'll find that Congress and NASA can continue to avoid facing reality for some considerable time to come.  :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline john smith 19

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*Conspiracy hat on

NASA is aware we aint going to Mars under current budgets. Deep Space Gateway is the nice way to do something in cislunar space while still plausibly pretending that it is all about going to Mars. Otherwise we risk being stuck in LEO for another several decades.

*Conspiracy hat off
Unless of course a large chunk of the HSF budget is freed up because Commercial Crew is unsustainable and they have to declare the ISS has to be retired.

Which would explain the persistent foot dragging in Congress and the Senate on appropriations to COTS and CC.

Not a conspiracy.

Merely a "coalition of the willing."  :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Proponent

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With the long time delay it looks like the government is dragging its feet waiting for commercial launch vehicles to become available. Commercial has the potential to reach the Lunar surface  and mars surface before SLS.

The economics with SLS are not there and now even more with 1st stage reuse. Congress and NASA needs to face reality !

And just now we have yet another reminder of how insanely expensive SLS is:  Bezos just announced that BO expects to spend about $2.5 billion developing the 45-tonne New Glenn.  That's only a bit more than NASA spends on SLS every year!  Suppose Bezos has got the cost wrong by a factor of two, and suppose that BO's cost to develop a launch vehicle twice the size were twice as much again (unlikely).  BO would then be able to produce an SLS-class rocket for less than 6 years' worth of SLS spending.  That means BO could develop an SLS-class lifter for less than will be spent on SLS just between now and the first flight of Block 1B!

Online jgoldader

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Quote from Gerst: "From our standpoint in HEOMD, it’s real important that we get some solid understanding of what the budget is."  Considering they want to launch a large SEP module in 5 years, am I wrong in believing they should have figured out the budget part already, especially since the SEP itself is pointless without the money to build something for it to push?
Recovering astronomer

Offline gosnold

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What kind of activities would be done in the Gateway? I don't see the point of it, it seems to me the Deep Space Transport could be launched and assembled without the Gateway.

Offline Proponent

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NASA is aware we aint going to Mars under current budgets. Deep Space Gateway is the nice way to do something in cislunar space while still plausibly pretending that it is all about going to Mars. Otherwise we risk being stuck in LEO for another several decades.

If I could suggest a rephrasing:

NASA is aware we it ain't going to Mars with Orion/SLS under current budgets. Deep Space Gateway is the nice way to build Orion/SLS and maybe do something in cislunar space while still plausibly pretending that it is all about going to Mars. Otherwise we risk NASA risks being stuck in LEO for another several decades.
« Last Edit: 04/07/2017 10:34 AM by Proponent »

Offline Proponent

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But SEP transfers cannot make use of the Oberth effect as they have too little thrust at perigee. They need to do a chemical burn at perigee, then use the SEP, but that just complicates things.

[pedantry]
You could get the full Oberth effect with SEP by performing many perigee passes and running the engine only near perigee.  But it would take a long time, and low-thrust trajectories are not about minimizing detla-V anyway (they more nearly maximize it).
[/pedantry]
« Last Edit: 04/07/2017 10:35 AM by Proponent »

Offline john smith 19

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And just now we have yet another reminder of how insanely expensive SLS is:  Bezos just announced that BO expects to spend about $2.5 billion developing the 45-tonne New Glenn.  That's only a bit more than NASA spends on SLS every year!  Suppose Bezos has got the cost wrong by a factor of two, and suppose that BO's cost to develop a launch vehicle twice the size were twice as much again (unlikely).  BO would then be able to produce an SLS-class rocket for less than 6 years' worth of SLS spending.  That means BO could develop an SLS-class lifter for less than will be spent on SLS just between now and the first flight of Block 1B!
Using the current versions of all major US LV's (Atlas V, Delta IV heavy, Antares and F9) the US could put 77 tonnes in LEO within slightly more than 1 week. Right now.

When SLC 40 comes back on line that will increase to 99 tonnes and assuming FH reaches projected capability that will increase to 140+ tonnes at a total launch purchase price  of less than roughly $1.5Bn

Without a single cent of taxpayers money being spent on LV development.

In its defense SLS gives you a fairing 10m across and that payload in a single block, and it might be able to launch a 2nd SLS faster than a 2nd salvo of them all together, putting another 140 tonnes up.

AFAIK the next biggest PLF is on the DIV H with 5m in dia by 60m long.

So the question is what payload absolutely has to be 10m across or cannot be made in less than a 100 tonne block?
« Last Edit: 04/07/2017 10:45 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Proponent

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Quote from Gerst: "From our standpoint in HEOMD, it’s real important that we get some solid understanding of what the budget is."  Considering they want to launch a large SEP module in 5 years, am I wrong in believing they should have figured out the budget part already, especially since the SEP itself is pointless without the money to build something for it to push?

I do strongly agree that, if sending humans BEO really is the whole point, the budget should have been mapped out a long time ago, like in 2010.  But I'm willing to be a little more lenient with regard to the large SEP stage, because it could be useful in a wide range of scenarios.

Offline Proponent

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If  a commercial crew capable of reaching DSG comes available,  then there is possibility of extra crew or private missions each year.

There is no need to wait and see whether such a thing is developed.  NASA could simply solicit bids for transportation services to and from DSG from American industry.

Offline Hotblack Desiato

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AFAIK the next biggest PLF is on the DIV H with 5m in dia by 60m long.

I think, 60m is a bit exaggerated.

According to ULA's user guide, it's 19.1m, which happens to be 62.7 ft. Still big, but not as long as falcon 9 (70m length).

Offline john smith 19

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AFAIK the next biggest PLF is on the DIV H with 5m in dia by 60m long.

I think, 60m is a bit exaggerated.

According to ULA's user guide, it's 19.1m, which happens to be 62.7 ft. Still big, but not as long as falcon 9 (70m length).
Damm I should have known that sounded too good to be true.

Boeing are saying SLS can offer a 10m Dia by 31m long PLF. with a volume of 1800 m^3. Only LH2 would not be mass limited for carrying as a propellant. All others would comfortably fit in the fairing up to the full payload of the vehicle.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Online envy887

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Well:  it's a plan.

But why again put a Deep Space Gateway in lunar orbit?  Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO.  Why not just start in LEO instead of getting everything out there to the Moon in the first place?

I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit.  But then why a gateway again?  I think that I'm missing a link in the logic chain . . .

The Oberth assist from L2/NRO/DRO is actually better than in LEO. The first maneuver to insert to a Earth transfer with a low perigee, where the velocity is over 3 km/s greater than LEO and already near escape. At perigee the Mars transfer burn is performed.

It's not as efficient as a direct transfer out of LEO, but high staging has a lot advantages for SEP transfers.

But SEP transfers cannot make use of the Oberth effect as they have too little thrust at perigee. They need to do a chemical burn at perigee, then use the SEP, but that just complicates things.

True. But if SEP is used for any leg of the trip than staging in cislunar space can be advantageous. E.g. using a SEP tug to bring a chemical departure stage up to L2, which can then do an Oberth-assisted departure burn and fast transit. Or using chemical rockets to quickly launch crew through the Van Allen belts, then using slower SEP to do the (non-Oberth) departure.

Offline AncientU

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I would have wished that NASA would have put the requirements out to the private sector for them to provide what they think the best solutions would be, and that way we'd also have the ability to assess what the cost trade-offs were for the different approaches.  But alas, we live in a different reality...

Yes, if this plan is NASA's (9th floor's) best shot at a public-private partnership, then we're not going anywhere fast.  Using the ISS model, NASA is proposing to put up the space station, now called Deep Space gateway, and then let a private company deliver supplies. 

NASA's way of saying, "Let them eat cake."
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline alexterrell

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Well:  it's a plan.

But why again put a Deep Space Gateway in lunar orbit?  Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO.  Why not just start in LEO instead of getting everything out there to the Moon in the first place?

I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit.  But then why a gateway again?  I think that I'm missing a link in the logic chain . . .

The Oberth assist from L2/NRO/DRO is actually better than in LEO. The first maneuver to insert to a Earth transfer with a low perigee, where the velocity is over 3 km/s greater than LEO and already near escape. At perigee the Mars transfer burn is performed.

It's not as efficient as a direct transfer out of LEO, but high staging has a lot advantages for SEP transfers.

But SEP transfers cannot make use of the Oberth effect as they have too little thrust at perigee. They need to do a chemical burn at perigee, then use the SEP, but that just complicates things.
But a hybrid approach could work...

Use SEP to lift all the mission, including fuel, but excluding crew, to L2/NRO/DRO. Then use chemical propellant from there.

Of course, that either needs storable propellants, or in-situ production from water. And it needs solar panel architectures that are not seriously impacted by transfers through the Van Allen belts.

The Earth - Surface to L2/NRO/DRO transport could also be tendered to the lowest cost bidder (SpaceX). That would leave NASA to operate the deep space mission.

Online Navier–Stokes

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True. But if SEP is used for any leg of the trip than staging in cislunar space can be advantageous. E.g. using a SEP tug to bring a chemical departure stage up to L2, which can then do an Oberth-assisted departure burn and fast transit. Or using chemical rockets to quickly launch crew through the Van Allen belts, then using slower SEP to do the (non-Oberth) departure.
I suspect that a chemical Oberth-assisted departure burn may be the plan. NASA describes DST as a "reusable vehicle that uses electric and chemical propulsion".

Offline alexterrell

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Boeing are saying SLS can offer a 10m Dia by 31m long PLF. with a volume of 1800 m^3. Only LH2 would not be mass limited for carrying as a propellant. All others would comfortably fit in the fairing up to the full payload of the vehicle.
Massive, foldable solar panels (for SEPs) might still be volume limited, as opposed to mass limited, depending on the designer's Origami skills.

So far the only useful thing that SLS can do that Falcon Heavy can't, is launch a 10m diameter, single piece heat shield for Mars reentry. I suppose a Bigelow BA-2100 would also count.

Speaking of which, why not use a Bigelow module as the core of the base?

Offline Khadgars

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With the long time delay it looks like the government is dragging its feet waiting for commercial launch vehicles to become available. Commercial has the potential to reach the Lunar surface  and mars surface before SLS.

The economics with SLS are not there and now even more with 1st stage reuse. Congress and NASA needs to face reality !

And just now we have yet another reminder of how insanely expensive SLS is:  Bezos just announced that BO expects to spend about $2.5 billion developing the 45-tonne New Glenn.  That's only a bit more than NASA spends on SLS every year!  Suppose Bezos has got the cost wrong by a factor of two, and suppose that BO's cost to develop a launch vehicle twice the size were twice as much again (unlikely).  BO would then be able to produce an SLS-class rocket for less than 6 years' worth of SLS spending.  That means BO could develop an SLS-class lifter for less than will be spent on SLS just between now and the first flight of Block 1B!

Do we have to have this discussion in every SLS thread?? This post has nothing to do with the OP article.

Offline Todd Martin

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I'm glad to see NASA layout more details on a plan. 

My biggest concern regarding manned flights to the Martian surface is the deleterious effect of long-duration weightlessness on the astronauts affecting their ability to function on the martian surface. 

I believe it would be much better if at least one of the Next-step DSH proposals offered artficial gravity (spinning the spacecraft). 

An expandable habitat (Let's call it a BA-DSH) designed for artificial gravity and able to fit in a 10 meter fairing would allow for a slower spin rate to achieve the desired level of artificial gravity and so minimize adverse affects of the coriolis force on humans.  I've based calculations on the BA-DSH spinning at 0.38G (Martian gravity).

With an expanded 15 meter diameter, spinning this structure to simulate Mars Gravity (0.38g) would result in 4.76rpm with a tangential speed of 7.48m/s, which should be acceptable.
 
As reference, Bigelow's BA2100 design proposal is 12m in diameter and 17.8m in length after inflation and fits in an 8 meter fairing with a weight around 67,500kg.  Overall density of the BA211 based on these outside dimensions is 33.5 kg/m 

A BA-DSH scaled to a 15 meter inflated diameter that fits in a 10 meter fairing and a length of 8 meters would weigh approximately 47 metric tons. 
 
« Last Edit: 04/07/2017 03:41 PM by Todd Martin »

Offline Oli

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Does anyone have a guess as to how long transit times from L2 to Mars might be with the DST and SEP?

Here:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160006328.pdf

Looks slow, but the minimum energy high-thrust trajectories for the same years do not offer much more stay time. Roughly ~25% more. See for example here on page 6: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150006952.pdf

The advantages of the SEP hybrid solution are, IMO: The use of proven and reliable pressure-fed hypergolic propulsion and electric propulsion, little fuel use and thus mass to be launched, a single transfer stage without any staging/refueling during the mission.

On the other hand an SEP stage of that size (425kw) still requires a large and potentially costly development program.
« Last Edit: 04/07/2017 04:27 PM by Oli »

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