Space Sunday: spaceplanes and landers

Artist’s impression of the Experimental Spaceplane XS-1, a joint venture between DARPA and Boeing and dubbed the “Phantom Express” by the latter. Credit: Boeing

Spaceplanes  – vehicles capable of operating like an aircraft with in the Earth’s atmosphere, and as a space vehicle either in orbit or while above altitudes of around 80-90 kilometres – are still relatively rare beasts, despite once being seen as the future of low-cost access to space. There have only really been a handful put to what might be called “operational” use. Most notably these include the space shuttle – more formally called the Space Transportation System, and the secretive X-37B “mini shuttle” operated by Boeing and the US Air Force.

Things will be changing in the future, most notably when the sub-orbital SpacePlaneTwo vehicle(s) operated by Virgin Galactic start “tourist” flights to the edge of space, and when the DreamChaser Cargo vehicle starts flying cargo payloads to the International Space Station in the 2020 – of which more below. A further vehicle set to enter operations in 2020/21 is the Experimental Spaceplane 1 (XS-1), which is quite a fascinating concept I’ve briefly covered in these pages.

A joint venture between the US Defence Advanced Research Projects Agency (DARPA) and Boeing, the latter having been awarded the phase 2 development contract by DARPA in late 2017, the uncrewed vehicle sit between the comparatively small X-37B and a space shuttle orbiter in size, being roughly comparable with and executive business jet. Dubbed the “Phantom Express” by Boeing, its primary goal is to offer a rapid launch and turn-around capability in deploying replacement, or urgently required, payloads to orbit. So rapid, in fact that as part of its test launch programme, a single XS-1 demonstrator must complete 10 launches in 10 days. In addition, the vehicle must be capable of hypersonic flight to around Mach 10 (12,250 km/h), and operate with a launch cost of around US $5 million per flight.

A sub-orbital vehicle, the XS-1 will not have an internal cargo bay; instead, the payload(s) will be mounted on one or two expendable boosters carried on its back, forming the system’s upper stage. This design allows the XS-1 to be a completely self-contained launcher: there is no booster system to help it into the skies, and no external tank for fuel.

To complete the XS-1, Boeing has partnered with Aerojet Rocketdyne, who will provide the vehicle’s primary motor – the AR-22. This is effectively an updated variant of the RS-25 Space Shuttle Main Engine (SSME), and has been selected because of the AR-25’s track record of space shuttle flights.

An artist’s impression of the XS-1 being readied for launch, a single payload upper stage mounted on its back. Credit: Boeing / DARPA

The XS-1 will fly out of Kennedy Space Centre, where Boeing already operate the X-37B and have vehicle processing facilities. It will launch vertically from a dedicated mobile launch platform, rather than a fixed pad. After climbing to altitude and clearing the denser part of the atmosphere, the spaceplane will release the payload booster, which delivers the payload to orbit, while the spaceplane makes an automated return to Florida, and make a landing either at the former space shuttle runway at Kennedy Space Centre or the Skid Strip at Cape Canaveral Air Force Station.

Phase 2 of the programme runs through until the end of 2019, and encompasses the design, construction and testing of a technology demonstration vehicle and the construction of the first AR-22 motors. One of these will be test-fired on the ground 10 times in 10 days to verify it is ready for flight tests. It comes at a cost of US $146 million to DARPA, with Boeing covering the remaining costs. The follow-on third phase of the project is due to commence in late 2019, and will include both 12 to 15 flight tests intended to confirm the atmospheric handling of the XS-1 spaceplane, and the 10 test launches in a 10-day time frame.

While developed as a DARPA programme, the XS-1 is not seen as being purely for government launches. Following the flight tests, DARPA and Boeing plan to release “selected data” from the test programme to commercial enterprises interested in leveraging the system’s low-cost, rapid launch capabilities.

Dream Chaser Cargo: SNC Weigh Launcher Options

Another spaceplane I’ve referenced in these updates is Sierra Nevada Corporation’s (SNC’s) Dream Chaser Cargo. Developed from an earlier variant of the vehicle SNC hoped would be used to ferry crews to and from the International Space Station (ISS), Dream Chaser Cargo is due to start delivering supplies to the ISS in 2020, alongside the current flights by the SpaceX Dragon and Orbital ATK Cygnus vehicles. During the 34th Space Symposium held in April 2018, SNC provided an update on their plans for Dream Chaser in general.

The vehicle has now entered its critical design review (CDR) with NASA, which is due to conclude in July 2018. This will clear the way for the construction of the first flight-ready version of Dream Chaser Cargo, which is due to fly in late 2020.

Sierra Nevada Corporation’s Dream Chaser test article has officially be placed in “semi-retirement” until the company is ready to resume work on a crewed variant of the vehicle. Credit: Sierra Nevada Corporation

In addition the company announced the flight test article, originally built for the crewed version of the Dream Chaser, is being retired and mothballed until such time as SNC is ready to resume it explorations in developing a crewed version of the vehicle, something which may be contingent on commercial interest and partners.

SNC is currently contracted to fly six resupply missions to the ISS between 2020 and 2024. In 2017, the company contracted United Launch Alliance for the first two Dream Chaser Cargo flights, using the Atlas 5 booster. However, at the symposium, SNC indicated it is looking to see if any can offer an alternative to ULA which, despite the reliability of their Atlas and Delta vehicles, are perhaps the most expensive of launch operators in the marketplace.


SNC’s uncrewed Dream Chaser Cargo,cutaway showing its internal cargo storage, and the International Berth and Docking Mechanism for the vehicle offering additional internal and external non-pressurised payload space, which will be supplied by the European Space Agency. Credit: SNC

The company recently issued a request for proposals for multiple Dream Chaser launches, and describes the response as “tremendous”. Most interestingly, while no statement on which launch operators have responded, the suggestion is that non-US players have expressed an interest. In discussing the RFI, SNC referenced the fact that resupply missions to the ISS have in the past been flown by the European Space Agency’s Automated Transfer Vehicles launched atop the Ariane launch vehicle, as well as the Japanese Kounotori H-II Transfer vehicle (which may fly three more missions to the ISS between 2019 and 2024). The intimation here being that perhaps a player like Europe’s Arianespace has expressed an interest in launching Dream Chaser missions to the ISS.

A decision on which – if any – alternative launch providers have been selected for Dream Chaser Cargo missions are under consideration is expected later in 2018.

Lunar Rover Cancelled, But Mission Not Dead

In 2017, the current US Administration effectively pivoted NASA’s course away from human missions to Mars to focus on a return to the Moon. In April 2018, the new-appointed NASA Administrator, Jim Bridenstine, cancelled what had been seen as a major player in preparing the way for human mission to the Moon.

The Resource Prospector (RP) mission had been in development for almost a decade, with a proposed launch date in 2022. It would have delivered a small rover vehicle in one of the lunar polar regions to carried out a survey expedition to detect and map the location of volatiles such as hydrogen, oxygen and lunar water which would be used by follow-on human missions to the Moon.

The prototype Lunar Resource Prospector rover undergoing tests. Credit: NASA

The decision to cancel the mission drew a sharp response from the scientists and engineers involved in the project via a letter to the new NASA Administrator.

This action is viewed with both incredulity and dismay by our community, especially as the President’s Space Policy Directive 1 directs NASA to go to the lunar surface. RP was the only polar lander-rover mission under development by NASA (in fact, by any nation, as all of the international missions to the lunar poles are static landers) and would have been ready for preliminary design review at the beginning of 2019.

– Letter on the cancellation of the Resource Prospector, sent to the NASA Administrator Bridenstine

The letter itself drew a clarification response from Bridenstine, indicating that selected instruments from Resource Prospector will be still be flown, but aboard commercial landers under the agency’s Commercial Lunar Payload Services (CLPS) programme. Initiated in March 2018, CLPs is intended to court commercial options for meeting the goal of establishing a human presence on the Moon. While primarily aimed at larger-scale options – crewed landers, habitat units, etc., – CLPS could also be used to develop smaller-scale missions, including robotic landers.

Bridenstine was keen to emphasise that the switch to using commercial carriers would allow for “an expanded lunar surface campaign. More landers. More science. More exploration. More prospectors. More commercial partners.”

Under CLPS, NASA plans to issue multiple  contracts to companies able to demonstrate their ability to deliver at least 10 kilograms of payload safely to the lunar surface by the end of 2021. The formal request for proposals is expected to be issued in July and several companies, including former competitors in the Google Lunar X-Prize competition, have already expressed an interest in working with NASA on launching payloads.

“We are very excited about NASA’s Commercial Lunar Payload Services program,” Bob Richards, chief executive of Moon Express, said April 28. “NASA has been a great technology development partner to Moon Express through the Lunar CATALYST program, and the CLPS program would enable us to apply that technology to small robotic missions supporting NASA’s goals of lunar science and exploration.”

One challenge in using any of the current Lunar X-Prize  landers is that none of them are currently capable of landing a Resource Prospector class of mission on the Moon – the rover vehicle is simply too heavy. However, Moon Express is starting development of a new class of lander which might be used in such missions, which could be ready for flight in 2021. In the meantime, NASA might aim to undertake the RP’s mission on a “modular” basis, across several commercial landers – hence the reference to flying selected RP instruments to the Moon on commercial landers.

Mar 2020 Suffers Heat Shield Crack

NASA’s Jet Propulsion Laboratory has confirmed that an element of the heat shield for the Mars 2020 rover mission cracked during testing earlier in the month at a Lockheed Martin facility near Denver. The fracture in the composite structure is located near the outer edge of the shield and spans its circumference, and occurred during testing in which it was subjected to forces 20 percent above those expected in a normal entry into the Martian atmosphere.

The damaged unit is one of three originally built for the Mars Science Laboratory (MSL) rover Curiosity. While one of these ultimately flew on that mission and the remaining two placed in storage for possible use with future Curiosity-class rover missions – like Mars 2020, allowing the agency to reduce development costs of such missions.

The Mars 2020 heat shield will experience temperatures up to 2,100 C (3,800 F) during the vehicle’s entry into the Martian atmosphere at a speed of around 19,500 kilometres per hour (12,100 mph). Credit: NASA

The damage to the heat shield means that NASA will have to replace it in order to have a back-up unit available should the remaining unit suffer damage during any further testing or during spacecraft integration prior to launch. However, this will not impact the mission’s slated mid-2020 launch date.

It had originally been hoped that the remained heat shield could be used with the sample return mission, designed to be a follow-on to the Mars 2020 mission, and intended to return samples gathered by the Mars 2020 rover and left in cylinders for later collection. However, this follow-up sample return mission has been in a state of flux. In August 2017 it was initially downsized to a “lean sample return mission”, ditching almost all of the associated science initially planned for it in favour on just focusing on sample unit recovery and return.

More recently, on April 26th, 2018, NASA and the European Space Agency (ESA) signed a statement of intent to study potential cooperation in developing aspects of a Mars sample return architecture. However, precisely what role each agency might have in any joint sample return mission is still to be decided. Some within Europe might also be cautious regarding any joint venture; around a decade ago, ESA entered into an agreement with NASA to fly the European ExoMars rover aboard a NASA-sponsored launch vehicle – only for NASA to pull out of the agreement in 2012, forcing a complete top-to-bottom redesign of the European rover, which contributed to significant delays in the ExoMars mission (now due to fly in 2020 as part of a joint European-Russian partnership).