A key lesson in unintended consequences that would-be #ClimateCrisis heroes may wish to be mindful of as they endeavor to save the planet from us humans. //

NotCoach | August 13, 2023 at 8:49 pm
Typically anything smaller than 25m in diameter will burn up in our atmosphere, depending on density, and considering these rocks were dislodged from the surface they are likely not very dense (mostly rock, little metal).

NotCoach in reply to NotCoach. | August 13, 2023 at 9:05 pm
As an example the Chelyabinsk meteor was estimated to be about 59 feet in diameter. It did not reach the surface of Earth. It exploded over Chelyabinsk Oblast with the force of 26 to 33 Hiroshimas, but the damage to Chelyabinsk Oblast was minimal because the blast was high up in the atmosphere. A 15 foot boulder is not a concern.

DovePig Ars Centurion
1y
6,274
mknelson said:
I was thinking gyroscopes, but see those stopped working in 2016.

Wikipedia notes: "Thrusters are supplied by a single 70-centimetre (28 in) diameter spherical titanium tank. It contained 100 kilograms (220 lb) of hydrazine at launch, providing enough fuel until 2034."
I am even much more in awe of the RCS mechanical valves, as even a hydrazine (or similar) propellent would probably still need some, as while you can apparently just run it over a rare metal catalyst screen to get it to decompose in a very exothermal reaction (these nitrogens really wanna go free!), you still have to push it through into the nozzle exactly when needed (and stop it when needed).

Come on, fifty years with a mechanical valve system in space? That still sounds awesome to me, even if IANARS! //

Needleroozer Smack-Fu Master, in training
10m
11
Subscriptor
Siosphere said:
How does Voyager 2 know where the earth is? Like how does it re-orient itself to earth?

What is it using as a reference point?
It appears to lock onto Canopus using a star-tracking system that rolls the spacecraft until a star of the appropriate intensity is detected, then maneuvers to stay centered on that star.

https://hackaday.com/2023/07/31/just-how-is-voyager-2-going-to-sort-out-its-dish-then/

NASA has detected a signal from Voyager 2 after nearly two weeks of silence from the interstellar spacecraft.

NASA's Jet Propulsion Laboratory said on Tuesday that a series of ground antennas, part of the Deep Space Network, had registered a carrier signal from Voyager 2 on Tuesday. //

NASA said it lost contact with Voyager 2, which is traveling 12.3 billion miles away from Earth, on Friday after "a series of planned commands" inadvertently caused the craft to turn its antenna 2 degrees away from the direction of its home planet. //

What might seem like a slight error had big consequences: NASA said it wouldn't be able to communicate with the craft until October, when the satellite would go through one of its routine repositioning steps. //

Last month's command mix-up means Voyager 2 is not able to transmit data back to Earth, but it also foreshadows the craft's inevitable end an estimated three years from now.

"Eventually, there will not be enough electricity to power even one instrument," reads a NASA page documenting the spacecraft's travels. "Then, Voyager 2 will silently continue its eternal journey among the stars."

Voyager 2's sister spacecraft, Voyager 1, meanwhile, is still broadcasting and transmitting data just fine from a slightly further vantage point of 15 billion miles away.

paw Ars Tribunus Militum 21y 1,984

dj__jg said:
I guess ESA has a shot at being a role model at de-orbiting stuff, since they sure aren't being a role model at putting stuff into orbit considering the delays and expendable nature of Ariane 6.

Let's not dump on ESA too much re being a role model. Ariane 5's outstanding launch of JWST, doubling its lifetime, should not be overlooked.

Honest question: have any NASA launches exceeded expectations by that much? //

Cloudgazer Ars Tribunus Angusticlavius 8y 15,517

paw said:
Let's not dump on ESA too much re being a role model. Ariane 5's outstanding launch of JWST, doubling its lifetime, should not be overlooked.

Honest question: have any NASA launches exceeded expectations by that much?

I'd love to know what the private opinion of the NASA team was about that launch. One way to view it is that ESA doubled the lifespan of JWST. Another is that they came within 30 m/s of disaster. //

Cloudgazer Ars Tribunus Angusticlavius 8y 15,517

Shiranui said:
How do you mean? How do you turn overdelivering on estimates into pessimistic relief?

Either I'm missing something about Arianespace having taken unnecessary risks to achieve this feat (which I have not heard of so far), or that's a very "glass half empty" perspective.

NASA had an estimated life based on ESA delivering JWST into the expected trajectory, JWST would then need to use its on board thrusters to get the perfect insertion into L2. There was never any doubt that Ariane had the grunt to get JWST into that orbit, or indeed beyond that orbit, but it was imperative that they not overshoot, because if they did JWST was lost.

The targeted trajectory NASA requested from Ariane left room at the top because of that. ESA ate into that margin which delivered a 'better' outcome, but the final adjustments by the JWST were a mere 23 m/s. Had they 'over delivered' by another 23m/s which they were quite capable of doing there would be no JWST.

Publically this was all praised as a great success, but I can't imagine it was quite the same story behind the scenes.

Think of it like shooting the proverbial apple off your wife's head. More points if you hit lower on the apple. This doesn't mean if you aimed for the middle and hit right at the bottom then your wife is going to be entirely happy, because a little lower and you're not a hero - you're William S Burroughs. //

Cloudgazer Ars Tribunus Angusticlavius 8y 15,517

Dan Homerick said:
While reading this, I was thinking "But couldn't JWST have rotated around and burned retrograde to correct a small overshoot?" And to answer that thought, I presume the answer is no, because then it'd be flying through it's own thruster plume, which would fog up the mirrors.

That right?

Kinda, that's half the story ..

More Than You Wanted to Know About Webb’s Mid-Course Corrections! – James Webb Space Telescope
https://blogs.nasa.gov/webb/2021/12/27/more-than-you-wanted-to-know-about-webbs-mid-course-corrections/

Webb has thrusters only on the warm, Sun-facing side of the observatory. We would not want the hot thrusters to contaminate the cold side of the observatory with unwanted heat or with rocket exhaust that could condense on the cold optics

So you're right about not wanting to fly through the plume, and that (along with other considerations) resulted in thrusters only on one side of the vehicle. But as a result of that design decision it's even worse than just contaminating the instrument

Webb’s Journey to L2 Is Nearly Complete – James Webb Space Telescope
https://blogs.nasa.gov/webb/2022/01/21/webbs-journey-to-l2-is-nearly-complete/

“So, why did the Ariane not give Webb more energy and why did Webb need course correction? If the Ariane had given Webb even a little bit too much energy than needed to get it to L2, it would be going too fast when it got there and would overshoot its desired science orbit. Webb would have to do a significant braking maneuver by thrusting toward the Sun to slow down. Not only would that big burn cost a lot of propellant, it would be impossible because it would require Webb to turn 180 degrees in order to thrust toward the Sun, which would have exposed its telescope optics and instruments directly to the Sun, thus overheating their structures and literally melting the glue that holds them together.

Like the enterprise in star trekkin the JWST is always going forwards 'cause they can't find reverse.

The observed and predicted ​Solar Cycle is depicted in Sunspot Number in the top graph and F10.7cm Radio Flux in the bottom graph.

In both plots, the black line represents the monthly averaged data and the purple line represents a 13-month weighted, smoothed version of the monthly averaged data. The slider bars below each plot provide the ability to display the sunspot data back to solar cycle 1 and F10.7 data back to 2004.

The mean forecast for the current solar cycle (Cycle 25) is given by the red line. This is based on an international panel that was convened in 2019 for this purpose. In February, 2023 the plot was modified to show the full range of the 2019 Panel prediction as the gray shaded region (similarly for the F10.7 cm plot). This takes into account expected uncertainties in the cycle start time and amplitude. Use the drop-down menu below each plot to display specific curves within this range.

The descent from lunar orbit to landing was broken into three phases, and each of these phases had a specific computer program associated with it. Here’s the way it worked on all six lunar landings:

The descent began with the braking phase — the first and longest phase. It was flown entirely automatically by the computer (Program 63). Its goal was to slow the spacecraft from about 3,800 miles/hour to about 700 miles/hour, and to decrease the LM’s altitude from about 50,000 feet to 7,000 feet.
The approach phase began when the LM was about 7,000 feet in altitude and about 2 miles from the landing site. The computer was still doing all the flying (Program 64), but the crew could now see the landing site and offer adjustments to the computer.
The landing phase began around 500 - 700 feet in altitude. The Commander flipped a switch next to his left thumb, causing the computer to switch to Program 66. The computer was now in what was known as attitude hold. The Commander selected the spot where he wanted to land, and used his controls to tell the computer where to go. The computer was also responsible for keeping the LM upright. The landing phase ends with the LM on the lunar surface. //

Here are the times (in minutes and seconds) that each of the missions spent in the landing phase:

Apollo 11: 2:23

Apollo 12: 1:44

Apollo 14: 2:01

Apollo 15: 1:16

Apollo 16: 1:00

Apollo 17: 1:08

Apollo 11 had by far the longest landing phase — almost 2 and a half minutes. That’s how long it took Armstrong to find a suitable landing spot and guide the computer toward it.

At the other extreme was Apollo 16 — when it entered the landing phase, a suitable landing spot was right there and it took John Young only a minute to guide the computer through the last few hundred feet and onto the lunar surface.

All of these missions went through the same phases — they differed only in how long each phase lasted.

As far as Armstrong being the one to fly the LM, that was also the plan, and again, it was the Commander who guided the LM during the landing phase on all six lunar landing missions. The job of the LMP (Lunar Module Pilot) was to provide crucial support during the landing, monitoring systems and calling out numbers throughout the landing phase. If you listen to the audio of any of the lunar landings, the voice you hear calling out numbers is the LMP.

Wickwick Ars Legatus Legionis
13y
30,072
Terakh said:

let's see the promises actually get delivered on "near" agreed upon time and cost given that some of the stuff don't even exist.

As long as Congress funds the programs on the agreed-upon schedules, I think both landers will be ready before their respective Artemis missions are flown.

Unfortunately, Congress has a history of reducing funding levels below what the delivery time requires then complaining that the programs are delayed. But those sorts of shenanigans only seem to happen to fixed-price contracts where they have no control over where and how the money is spent. The cost-plus rocket contracts seem immune to any sorts of cuts. //

EricBerger Ars Scholae Palatinae
7y
1,067
ARS STAFF
pipe13 said:

...and a large source of energy. You know, to mine the water, collect the CO2, and put the proverbial toothpaste back in the tube.

The numbers are pretty sobering: Approximately 750 kilowatts of continuous energy, for two years, to produce 1,000 tons of liquid oxygen and methane. //

RichyRoo Wise, Aged Ars Veteran
5y
113
Subscriptor
Hopefully Smarter said:

I love seeing the enthusiasm about spreading the toxic virus of humanity throughout the universe.

without us there is no point to the rest of the universe //

abie Ars Scholae Palatinae
5y
719
Hopefully Smarter said:

I love seeing the enthusiasm about spreading the toxic virus of humanity throughout the universe.

What you call a toxic virus, I call the light of consciousness. We've found no signs of life anywhere in the universe. Life might be incredibly rare, intelligent life rarer still. Taking the first hesitant steps to establishing life off Earth should be a cause for celebration, not miserable cynicism such as yours.

Last Friday, NASA awarded a $3.4 billion contract to a team led by Blue Origin for the design and construction of a second Human Landing System to fly astronauts down to the Moon.

The announcement capped a furious two-year lobbying campaign by Blue Origin owner Jeff Bezos to obtain a coveted piece of NASA's Artemis program. NASA also notched a big win, gaining the competition with SpaceX it sought for landing services. But there is a more profound takeaway from this.

After losing the initial lander contract to SpaceX two years ago, Blue Origin did not just bid a lower price this time around. Instead, it radically transformed the means by which it would put humans on the Moon. The Blue Moon lander is now completely reusable; it will remain in lunar orbit, going up and down to the surface. It will be serviced by a transport vehicle that will be fueled in low-Earth orbit and then deliver propellant to the Moon. This transporter, in turn, will be refilled by multiple launches of the reusable New Glenn rocket.

To be sure, that is a lot of hardware that has yet to be built and tested. But when we step back, there is one inescapable fact. With SpaceX's fully reusable Starship, and now Blue Moon, NASA has selected two vehicles based around the concept of many launches and the capability to store and transfer propellant in space.

This is a remarkable transformation in the way humans will explore outer space—potentially the biggest change in spaceflight since the Soviet Union launched the Sputnik satellite in 1957. It has been a long time coming. //

The German physicist Max Planck is credited with the notion that science advances only when older practitioners die off, leaving room for new ideas. The philosopher of science Thomas Kuhn more pithily summarized the sentiment by writing, "Science advances one funeral at a time."

Goff offered a variation on this idea for spaceflight: "Space policy seems to progress one congressional retirement at a time," he said.

Like Sowers, he welcomed NASA's entry into an era of reusable spaceflight. But Goff noted that it is really only happening because two billionaires, Elon Musk and Jeff Bezos, are aggressively pushing the idea forward.

NASA has spent so much over the last decade on the development of the SLS rocket—north of $40 billion, including ground systems—that there has been little money left over for exploration payloads to fly on them. Therefore, when it came time to fund the lunar landers, NASA had to go with the least expensive options. Both Starship and Blue Moon are, roughly, at least $10 billion development programs. But because it can purchase them with fixed-price contracts, NASA is only paying about a third of the overall cost for both, $6.3 billion.

"The only way NASA could really afford to do this was by not doing business as usual," Goff said.

An independent report published Thursday had troubling findings about the money spent by the agency on propulsion for the Space Launch System rocket. Moreover, the report by NASA Inspector General Paul Martin warns that if these costs are not controlled, it could jeopardize plans to return to the Moon. //

"The agency’s reliance on cost-plus awards increases its financial risk," Martin wrote. "In our judgment, NASA has used cost-plus contracting structures for its SLS booster and engine contracts to a greater extent than warranted. Although the SLS is a new vehicle, its heritage boosters and RS-25 engines are well-established."

Cost-plus contracts pay the recipient the total amount of their costs plus a fee. This is in contrast to the fixed-price contracts NASA has given SpaceX and Blue Origin for landers, the design of which is much more experimental and cutting-edge in nature than repurposing space shuttle hardware. //

For example, the current cost of manufacturing a new RS-25 main engine—which will be used for the Artemis V mission and onward—is about $100 million. NASA and Aerojet are trying to achieve a 30 percent cost savings by the end of this decade, bringing the cost down to $70.5 million. //

Compared to the private sector, even getting the cost of an RS-25 engine down to $70.5 million is a preposterously high price. Blue Origin manufactures engines of comparable power and size, the BE-4, for less than $20 million. And SpaceX is seeking to push the similarly powerful Raptor rocket engine costs even lower, to less than $1 million per engine.

Based on all of the new data in his latest report, Martin said his office has had to revise its estimate of the total cost of a Space System Launch, inclusive of ground systems and the Orion spacecraft. It is now $4.2 billion.

NASA’s plan to spend up to $1 billion on a tug to deorbit the International Space Station is a missed opportunity to instead repurpose or recycle the station, some in industry argue.

NASA announced plans as part of its fiscal year 2024 budget proposal this month to develop the tug to help deorbit the station at the end of its life in 2030. NASA is seeking $180 million in 2024 to start work on the tug, and anticipates spending as much as $1 billion to build it.

The agency had made clear that it and the other partners would deorbit the station at the end of its life, ensuring that debris that survives reentry falls in an uninhabited region of the South Pacific Ocean to avoid the risk of damage or casualties. NASA previously expected that it would use multiple Progress cargo spacecraft to handle the deorbiting, but said at a March 13 event about the budget proposal it chose to develop the tug to provide redundancy in those plans.

Most of the orbital change came from the momentum carried away by debris. //

When the NASA DART mission slammed into a small asteroid, we knew with great precision how much the spacecraft weighed and how fast it traveled. If you combine that with our estimates of the motion and mass of its target asteroid, Dimorphos, then you could easily do the math and estimate how much momentum would be lost by the asteroid and what that would mean for its orbit. That bit of math would suggest that Dimorphos' orbit should end up roughly seven minutes shorter.

Instead, the orbit was shortened by a half hour—over four times that number. //

Today's issue of Nature contains five articles that collectively reconstruct the impact and its aftermath to explain how DART's collision had an outsized effect. And, in the process, the articles indicate that impactors like DART could be a viable means of protecting the planet from small asteroids. //

This shows that we currently have the technology needed to run an interception on a small asteroid without requiring elaborate reconnaissance in advance. And, as we've known for some time, the impact of the spacecraft can significantly shift the orbit of the asteroid. So, from the planetary-defense perspective, DART was a major validation.

Most of the remaining new information focuses on why the orbital shift was so much larger than a simple calculation might suggest. //

Eject!
Potential impact models had already indicated that there was an additional way that DART could influence the orbital momentum of Dimorphos. Because the asteroid is likely to be a "rubble pile" of material loosely held together by gravity, any impact was likely to send some of that material shooting off the surface of the asteroid. And all of that material would carry momentum of its own, directed away from the site of impact—which was located on the surface that faced toward Dimorphos' direction of orbit. So, the equal and opposite reaction to the ejecta would be a slowing down of the asteroid's orbit, which would be added to the effect of DART's impact.

The maximum expected change in the orbital period in these models was 40 minutes. Since the orbit changed by 30 minutes, this suggests that the amount of material sent off by DART's impact was on the high side of potential scenarios.

Hasselblad and NASA’s journey together began in 1962 during the Mercury program. Prospective NASA astronaut and photography enthusiast Walter Schirra had his own Hasselblad 500C with a Planar f/2.8, 80mm lens. Knowing the high quality of the Hasselblad camera, Schirra suggested to NASA that they use a Hasselblad to document space since the previous camera model utilised delivered disappointing results. After buying a few 500Cs, a weight-loss program followed including removal of its leather covering, auxiliary shutter, reflex mirror, and viewfinder. A new film magazine was constructed in order to allow for 70 exposures instead of the usual 12. Finally, a matte black outer paint job minimized reflections in the window of the orbiter. The streamlined Hasselblad would find itself in the payload for Mercury 8 (MA-8) in October 1962. The successful, high quality images that Schirra captured across his six orbits of the Earth would spark a new chapter in the history of Hasselblad and a long, close and mutually beneficial cooperation between the American space agency and the Swedish camera manufacturer.

She calculated the trajectory for Alan Shepard, the first American in space. Even after NASA began using electronic computers, John Glenn requested that she personally recheck the calculations made by the new electronic computers before his flight aboard Friendship 7 – the mission on which he became the first American to orbit the Earth. She continued to work at NASA until 1986, combining her math talent with electronic computer skills. Her calculations proved critical to the success of the Apollo Moon landing program and the start of the Space Shuttle program. //

https://youtu.be/E4j_LpKzcZQ //

A wonderful interview with Johnson where she gets to tell you her story. The interview is 22 minutes and well worth the time.

https://youtu.be/r8gJqKyIGhE

There aren’t many DC-8s left flying in the world today, but there’s one special airplane that is set to have an extended life in a very interesting role. NASA took on a Douglas DC-8 in February 1986 and has been operating it ever since as a flying science laboratory. Here’s what you need to know.

The National Aeronautics and Space Administration (NASA) is preparing to say goodbye to its old but iconic Douglas DC-8. NASA has operated the Douglas quadjet for decades, first taking it in February 1986, and using it ever since as a flying science laboratory.

The airplane was not new when it arrived with NASA, having originally been delivered to Alitalia in 1969 and flying with Braniff from 1979 until 1986. For NASA, it flies under registration N817NA, and is used to collect data for a range of experiments on behalf of the world’s scientific community, with operations costing scientists approximately $6,500 per hour.
NASA DC-8 flying science lab
Photo: NASA

The DC-8-72 is now approaching 54 years old, and despite being meticulously maintained by NASA, she is reaching the end of her useful life. As such, the Administration has lined up a replacement for the jet - a Boeing 777. //

The DC-8 is fast becoming a rare breed in terms of aircraft still flying. Just three airplanes are listed as being in active service today, the other two with Trans Air Cargo Service, according to ch-aviation. A further two are in maintenance just now, suggesting they could soon fly again. One operates for humanitarian purposes with Samaritan’s Purse, while the other is taken care of by SkyBus Cargo Charters.

After launching on a Falcon 9 rocket in August 2022, the Korean Pathfinder Lunar Orbiter slid into orbit around the Moon last month. This was South Korea's first lunar probe, and among its chief objectives was surveying the polar regions of the Moon for resources such as water ice.

One of the six instruments carried by the half-ton satellite was a hyper-sensitive camera built by NASA called ShadowCam. The camera was designed with maximum sensitivity to light, such that it could provide images of permanently shadowed regions of the poles—which is to say, capture images of things that are inherently very dark.

Earlier this week, the ShadowCam team released its first image, which reveals a wall and the floor of Shackleton Crater near the south pole of the Moon. At first glance, there's nothing remarkable about the photo. It looks a lot like... the Moon.

However, what you're actually looking at is an area of the Moon that lies in total darkness. Here is a photograph taken by NASA's Lunar Reconnaissance Orbiter in 2009, shortly after it reached the Moon. That black area on the left of the photo? That's the region of Shackleton Crater imaged by ShadowCam. Yeah, it's pretty phenomenal. //

According to the imaging team, the camera's ability to capture clear images at high sensitivity is the equivalent of increasing from ISO 100 to greater than 12,800 without increasing grain.

On September 22, 2022 NASA and SpaceX announced that they were investigating the possibility of using a Dragon spacecraft—of the kind used to ferry NASA astronauts to the International Space Station—to go visit Hubble. On Dec. 22 NASA issued a request for other commercial space companies to get involved. //

The idea is that Hubble could be boosted to a higher orbit to continue its work for many more years. There’s also the tantalising prospect that it could also be serviced and refurbished—and its optics improved. //

A general servicing would be crucial because whether or not Hubble avoids re-entry this decade it is getting old. Launched in 1990 and last serviced by a space shuttle crew in 2009, it’s beginning to have technical problems. The latest was in July 2021 when it spent a month out of action because its payload computer failed before the problem was fixed.

However, from a science point of view an upgrade to its optics would be a game-changer. The reflecting telescope has a 2.4 meter mirror that can’t be upgraded, but its cameras could be. //

If the feasibility studies suggests it’s a go-er it would be the sixth time Hubble has been visited since its launch from Space Shuttle Discovery on April 24, 1990. //

Almost immediately after its launch it was discovered that its mirror had an aberration causing images to be blurry, so it was visited in orbit by astronauts aboard NASA’s Space Shuttle Endeavour in 1993. They installed corrective optics. More servicing missions took place in 1997, 1999, 2002 and 2009 to upgrade various components, notably adding the telescope’s Wide Field Camera 3.

Hubble now has six cameras and sensors to gather data on and take spectacular images of deep sky targets previously beyond the reach of astronomers. There are larger ground-based telescopes, but their view of the cosmos is limited by Earth’s atmosphere, which blocks infrared and ultraviolet light.

Hubble remains valuable to astronomers—and continues to make incredible observations—because it sees the universe in ultraviolet, visible and near-infrared light. The new James Webb Space Telescope deals only in near and far-infrared light. Since Webb orbits the Sun a million miles from Earth it can likely never be serviced—despite repeated strikes by micrometeoroids already.

Webb's Latest Image Galleries: Recent | First Images | Test | In Depth

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There are also valid concerns about the safety of the SLS and Orion hardware. These vehicles are large, complex machines that will only fly infrequently, at most once a year. At such a flight rate, this launch system will always be experimental.

It can reasonably be argued that Starship is also not safe to launch on and land back on Earth. It, too, is a large and complex vehicle that will come back through Earth's atmosphere, dissipate heat, and perform delicate maneuvers before landing under the power of its own engines. Even though Starship will launch at least dozens of times per year, the vehicle is unlikely to meet NASA's safety requirements for humans for a long, long time. So Starship-only missions to the Moon are not a near-term solution.

Something even the prophet cannot predict
However, there is an alternative, the source suggested. NASA presently has a vehicle it has deemed safe enough to launch humans into space and back. That's SpaceX's Crew Dragon spacecraft, which launches on the rocket that owns the world record for the longest streak of successful launches—the Falcon 9. By the mid-2020s, Crew Dragon will already have launched humans into space dozens of times.

The safest and lowest-cost means of completing an Artemis mission to the Moon, therefore, may involve four astronauts launching to a fairly high altitude in low-Earth orbit on Crew Dragon and rendezvousing with a fully fueled Starship. The astronauts would then fly to the Moon, land, and come back to rendezvous with Crew Dragon in Earth orbit. They would then splash down on Earth inside Dragon.

This architecture is less risky because it doesn't involve launching on SLS, nor does it require two rendezvous and dockings in lunar orbit, far from Earth. The crew would only spend a couple of more days aboard Starship than they would during the existing Artemis III plan, so Starship life support should be up to the task. If you care about costs, this plan also excludes the $4.1 billion launch cost of Orion and the SLS rocket and substitutes Crew Dragon, which would be on the order of one-twentieth of the cost.